USB: g_mass_storage: testing code from f_mass_storage.c removed

[linux-2.6.git] / drivers / usb / gadget / f_mass_storage.c

/*
 * file_storage.c -- File-backed USB Storage Gadget, for USB development
 *
 * Copyright (C) 2003-2008 Alan Stern
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The names of the above-listed copyright holders may not be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * ALTERNATIVELY, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") as published by the Free Software
 * Foundation, either version 2 of that License or (at your option) any
 * later version.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


/*
 * The File-backed Storage Gadget acts as a USB Mass Storage device,
 * appearing to the host as a disk drive or as a CD-ROM drive.  In addition
 * to providing an example of a genuinely useful gadget driver for a USB
 * device, it also illustrates a technique of double-buffering for increased
 * throughput.  Last but not least, it gives an easy way to probe the
 * behavior of the Mass Storage drivers in a USB host.
 *
 * Backing storage is provided by a regular file or a block device, specified
 * by the "file" module parameter.  Access can be limited to read-only by
 * setting the optional "ro" module parameter.  (For CD-ROM emulation,
 * access is always read-only.)  The gadget will indicate that it has
 * removable media if the optional "removable" module parameter is set.
 *
 * There is support for multiple logical units (LUNs), each of which has
 * its own backing file.  The number of LUNs can be set using the optional
 * "luns" module parameter (anywhere from 1 to 8), and the corresponding
 * files are specified using comma-separated lists for "file" and "ro".
 * The default number of LUNs is taken from the number of "file" elements;
 * it is 1 if "file" is not given.  If "removable" is not set then a backing
 * file must be specified for each LUN.  If it is set, then an unspecified
 * or empty backing filename means the LUN's medium is not loaded.  Ideally
 * each LUN would be settable independently as a disk drive or a CD-ROM
 * drive, but currently all LUNs have to be the same type.  The CD-ROM
 * emulation includes a single data track and no audio tracks; hence there
 * need be only one backing file per LUN.  Note also that the CD-ROM block
 * length is set to 512 rather than the more common value 2048.
 *
 * Requirements are modest; only a bulk-in and a bulk-out endpoint are
 * needed (an interrupt-out endpoint is also needed for CBI).  The memory
 * requirement amounts to two 16K buffers, size configurable by a parameter.
 * Support is included for both full-speed and high-speed operation.
 *
 * Note that the driver is slightly non-portable in that it assumes a
 * single memory/DMA buffer will be useable for bulk-in, bulk-out, and
 * interrupt-in endpoints.  With most device controllers this isn't an
 * issue, but there may be some with hardware restrictions that prevent
 * a buffer from being used by more than one endpoint.
 *
 * Module options:
 *
 *      file=filename[,filename...]
 *                              Required if "removable" is not set, names of
 *                                      the files or block devices used for
 *                                      backing storage
 *      ro=b[,b...]             Default false, booleans for read-only access
 *      removable               Default false, boolean for removable media
 *      luns=N                  Default N = number of filenames, number of
 *                                      LUNs to support
 *      stall                   Default determined according to the type of
 *                                      USB device controller (usually true),
 *                                      boolean to permit the driver to halt
 *                                      bulk endpoints
 *      cdrom                   Default false, boolean for whether to emulate
 *                                      a CD-ROM drive
 *
 * The pathnames of the backing files and the ro settings are available in
 * the attribute files "file" and "ro" in the lun<n> subdirectory of the
 * gadget's sysfs directory.  If the "removable" option is set, writing to
 * these files will simulate ejecting/loading the medium (writing an empty
 * line means eject) and adjusting a write-enable tab.  Changes to the ro
 * setting are not allowed when the medium is loaded or if CD-ROM emulation
 * is being used.
 *
 * This gadget driver is heavily based on "Gadget Zero" by David Brownell.
 * The driver's SCSI command interface was based on the "Information
 * technology - Small Computer System Interface - 2" document from
 * X3T9.2 Project 375D, Revision 10L, 7-SEP-93, available at
 * <http://www.t10.org/ftp/t10/drafts/s2/s2-r10l.pdf>.  The single exception
 * is opcode 0x23 (READ FORMAT CAPACITIES), which was based on the
 * "Universal Serial Bus Mass Storage Class UFI Command Specification"
 * document, Revision 1.0, December 14, 1998, available at
 * <http://www.usb.org/developers/devclass_docs/usbmass-ufi10.pdf>.
 */


/*
 *                              Driver Design
 *
 * The FSG driver is fairly straightforward.  There is a main kernel
 * thread that handles most of the work.  Interrupt routines field
 * callbacks from the controller driver: bulk- and interrupt-request
 * completion notifications, endpoint-0 events, and disconnect events.
 * Completion events are passed to the main thread by wakeup calls.  Many
 * ep0 requests are handled at interrupt time, but SetInterface,
 * SetConfiguration, and device reset requests are forwarded to the
 * thread in the form of "exceptions" using SIGUSR1 signals (since they
 * should interrupt any ongoing file I/O operations).
 *
 * The thread's main routine implements the standard command/data/status
 * parts of a SCSI interaction.  It and its subroutines are full of tests
 * for pending signals/exceptions -- all this polling is necessary since
 * the kernel has no setjmp/longjmp equivalents.  (Maybe this is an
 * indication that the driver really wants to be running in userspace.)
 * An important point is that so long as the thread is alive it keeps an
 * open reference to the backing file.  This will prevent unmounting
 * the backing file's underlying filesystem and could cause problems
 * during system shutdown, for example.  To prevent such problems, the
 * thread catches INT, TERM, and KILL signals and converts them into
 * an EXIT exception.
 *
 * In normal operation the main thread is started during the gadget's
 * fsg_bind() callback and stopped during fsg_unbind().  But it can also
 * exit when it receives a signal, and there's no point leaving the
 * gadget running when the thread is dead.  So just before the thread
 * exits, it deregisters the gadget driver.  This makes things a little
 * tricky: The driver is deregistered at two places, and the exiting
 * thread can indirectly call fsg_unbind() which in turn can tell the
 * thread to exit.  The first problem is resolved through the use of the
 * REGISTERED atomic bitflag; the driver will only be deregistered once.
 * The second problem is resolved by having fsg_unbind() check
 * fsg->state; it won't try to stop the thread if the state is already
 * FSG_STATE_TERMINATED.
 *
 * To provide maximum throughput, the driver uses a circular pipeline of
 * buffer heads (struct fsg_buffhd).  In principle the pipeline can be
 * arbitrarily long; in practice the benefits don't justify having more
 * than 2 stages (i.e., double buffering).  But it helps to think of the
 * pipeline as being a long one.  Each buffer head contains a bulk-in and
 * a bulk-out request pointer (since the buffer can be used for both
 * output and input -- directions always are given from the host's
 * point of view) as well as a pointer to the buffer and various state
 * variables.
 *
 * Use of the pipeline follows a simple protocol.  There is a variable
 * (fsg->next_buffhd_to_fill) that points to the next buffer head to use.
 * At any time that buffer head may still be in use from an earlier
 * request, so each buffer head has a state variable indicating whether
 * it is EMPTY, FULL, or BUSY.  Typical use involves waiting for the
 * buffer head to be EMPTY, filling the buffer either by file I/O or by
 * USB I/O (during which the buffer head is BUSY), and marking the buffer
 * head FULL when the I/O is complete.  Then the buffer will be emptied
 * (again possibly by USB I/O, during which it is marked BUSY) and
 * finally marked EMPTY again (possibly by a completion routine).
 *
 * A module parameter tells the driver to avoid stalling the bulk
 * endpoints wherever the transport specification allows.  This is
 * necessary for some UDCs like the SuperH, which cannot reliably clear a
 * halt on a bulk endpoint.  However, under certain circumstances the
 * Bulk-only specification requires a stall.  In such cases the driver
 * will halt the endpoint and set a flag indicating that it should clear
 * the halt in software during the next device reset.  Hopefully this
 * will permit everything to work correctly.  Furthermore, although the
 * specification allows the bulk-out endpoint to halt when the host sends
 * too much data, implementing this would cause an unavoidable race.
 * The driver will always use the "no-stall" approach for OUT transfers.
 *
 * One subtle point concerns sending status-stage responses for ep0
 * requests.  Some of these requests, such as device reset, can involve
 * interrupting an ongoing file I/O operation, which might take an
 * arbitrarily long time.  During that delay the host might give up on
 * the original ep0 request and issue a new one.  When that happens the
 * driver should not notify the host about completion of the original
 * request, as the host will no longer be waiting for it.  So the driver
 * assigns to each ep0 request a unique tag, and it keeps track of the
 * tag value of the request associated with a long-running exception
 * (device-reset, interface-change, or configuration-change).  When the
 * exception handler is finished, the status-stage response is submitted
 * only if the current ep0 request tag is equal to the exception request
 * tag.  Thus only the most recently received ep0 request will get a
 * status-stage response.
 *
 * Warning: This driver source file is too long.  It ought to be split up
 * into a header file plus about 3 separate .c files, to handle the details
 * of the Gadget, USB Mass Storage, and SCSI protocols.
 */


/* #define VERBOSE_DEBUG */
/* #define DUMP_MSGS */


#include <linux/blkdev.h>
#include <linux/completion.h>
#include <linux/dcache.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/kref.h>
#include <linux/kthread.h>
#include <linux/limits.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/freezer.h>
#include <linux/utsname.h>

#include <linux/usb/ch9.h>
#include <linux/usb/gadget.h>

#include "gadget_chips.h"



/*
 * Kbuild is not very cooperative with respect to linking separately
 * compiled library objects into one module.  So for now we won't use
 * separate compilation ... ensuring init/exit sections work to shrink
 * the runtime footprint, and giving us at least some parts of what
 * a "gcc --combine ... part1.c part2.c part3.c ... " build would.
 */
#include "usbstring.c"
#include "config.c"
#include "epautoconf.c"

/*-------------------------------------------------------------------------*/

#define DRIVER_DESC             "File-backed Storage Gadget"
#define DRIVER_NAME             "g_file_storage"
#define DRIVER_VERSION          "20 November 2008"

static       char fsg_string_manufacturer[64];
static const char fsg_string_product[] = DRIVER_DESC;
static       char fsg_string_serial[13];
static const char fsg_string_config[] = "Self-powered";
static const char fsg_string_interface[] = "Mass Storage";


#define FSG_NO_INTR_EP 1

#include "storage_common.c"


MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_AUTHOR("Alan Stern");
MODULE_LICENSE("Dual BSD/GPL");

/*
 * This driver assumes self-powered hardware and has no way for users to
 * trigger remote wakeup.  It uses autoconfiguration to select endpoints
 * and endpoint addresses.
 */


/*-------------------------------------------------------------------------*/


/* Encapsulate the module parameter settings */

static struct {
        char            *file[FSG_MAX_LUNS];
        int             ro[FSG_MAX_LUNS];
        unsigned int    num_filenames;
        unsigned int    num_ros;
        unsigned int    nluns;

        int             removable;
        int             can_stall;
        int             cdrom;

        unsigned short  release;
} mod_data = {                                  // Default values
        .removable              = 0,
        .can_stall              = 1,
        .cdrom                  = 0,
        };


module_param_array_named(file, mod_data.file, charp, &mod_data.num_filenames,
                S_IRUGO);
MODULE_PARM_DESC(file, "names of backing files or devices");

module_param_array_named(ro, mod_data.ro, bool, &mod_data.num_ros, S_IRUGO);
MODULE_PARM_DESC(ro, "true to force read-only");

module_param_named(luns, mod_data.nluns, uint, S_IRUGO);
MODULE_PARM_DESC(luns, "number of LUNs");

module_param_named(removable, mod_data.removable, bool, S_IRUGO);
MODULE_PARM_DESC(removable, "true to simulate removable media");

module_param_named(stall, mod_data.can_stall, bool, S_IRUGO);
MODULE_PARM_DESC(stall, "false to prevent bulk stalls");

module_param_named(cdrom, mod_data.cdrom, bool, S_IRUGO);
MODULE_PARM_DESC(cdrom, "true to emulate cdrom instead of disk");


/*-------------------------------------------------------------------------*/


struct fsg_dev {
        /* lock protects: state, all the req_busy's, and cbbuf_cmnd */
        spinlock_t              lock;
        struct usb_gadget       *gadget;

        /* filesem protects: backing files in use */
        struct rw_semaphore     filesem;

        /* reference counting: wait until all LUNs are released */
        struct kref             ref;

        struct usb_ep           *ep0;           // Handy copy of gadget->ep0
        struct usb_request      *ep0req;        // For control responses
        unsigned int            ep0_req_tag;
        const char              *ep0req_name;

        unsigned int            bulk_out_maxpacket;
        enum fsg_state          state;          // For exception handling
        unsigned int            exception_req_tag;

        u8                      config, new_config;

        unsigned int            running : 1;
        unsigned int            bulk_in_enabled : 1;
        unsigned int            bulk_out_enabled : 1;
        unsigned int            phase_error : 1;
        unsigned int            short_packet_received : 1;
        unsigned int            bad_lun_okay : 1;

        unsigned long           atomic_bitflags;
#define REGISTERED              0
#define IGNORE_BULK_OUT         1

        struct usb_ep           *bulk_in;
        struct usb_ep           *bulk_out;

        struct fsg_buffhd       *next_buffhd_to_fill;
        struct fsg_buffhd       *next_buffhd_to_drain;
        struct fsg_buffhd       buffhds[FSG_NUM_BUFFERS];

        int                     thread_wakeup_needed;
        struct completion       thread_notifier;
        struct task_struct      *thread_task;

        int                     cmnd_size;
        u8                      cmnd[MAX_COMMAND_SIZE];
        enum data_direction     data_dir;
        u32                     data_size;
        u32                     data_size_from_cmnd;
        u32                     tag;
        unsigned int            lun;
        u32                     residue;
        u32                     usb_amount_left;

        unsigned int            nluns;
        struct fsg_lun          *luns;
        struct fsg_lun          *curlun;
};

typedef void (*fsg_routine_t)(struct fsg_dev *);

static int exception_in_progress(struct fsg_dev *fsg)
{
        return (fsg->state > FSG_STATE_IDLE);
}

/* Make bulk-out requests be divisible by the maxpacket size */
static void set_bulk_out_req_length(struct fsg_dev *fsg,
                struct fsg_buffhd *bh, unsigned int length)
{
        unsigned int    rem;

        bh->bulk_out_intended_length = length;
        rem = length % fsg->bulk_out_maxpacket;
        if (rem > 0)
                length += fsg->bulk_out_maxpacket - rem;
        bh->outreq->length = length;
}

static struct fsg_dev                   *the_fsg;
static struct usb_gadget_driver         fsg_driver;


/*-------------------------------------------------------------------------*/

static int fsg_set_halt(struct fsg_dev *fsg, struct usb_ep *ep)
{
        const char      *name;

        if (ep == fsg->bulk_in)
                name = "bulk-in";
        else if (ep == fsg->bulk_out)
                name = "bulk-out";
        else
                name = ep->name;
        DBG(fsg, "%s set halt\n", name);
        return usb_ep_set_halt(ep);
}


/*-------------------------------------------------------------------------*/

/*
 * DESCRIPTORS ... most are static, but strings and (full) configuration
 * descriptors are built on demand.  Also the (static) config and interface
 * descriptors are adjusted during fsg_bind().
 */

/* There is only one configuration. */
#define CONFIG_VALUE            1

static struct usb_device_descriptor
device_desc = {
        .bLength =              sizeof device_desc,
        .bDescriptorType =      USB_DT_DEVICE,

        .bcdUSB =               cpu_to_le16(0x0200),
        .bDeviceClass =         USB_CLASS_PER_INTERFACE,

        /* The next three values can be overridden by module parameters */
        .idVendor =             cpu_to_le16(FSG_VENDOR_ID),
        .idProduct =            cpu_to_le16(FSG_PRODUCT_ID),
        .bcdDevice =            cpu_to_le16(0xffff),

        .iManufacturer =        FSG_STRING_MANUFACTURER,
        .iProduct =             FSG_STRING_PRODUCT,
        .iSerialNumber =        FSG_STRING_SERIAL,
        .bNumConfigurations =   1,
};

static struct usb_config_descriptor
config_desc = {
        .bLength =              sizeof config_desc,
        .bDescriptorType =      USB_DT_CONFIG,

        /* wTotalLength computed by usb_gadget_config_buf() */
        .bNumInterfaces =       1,
        .bConfigurationValue =  CONFIG_VALUE,
        .iConfiguration =       FSG_STRING_CONFIG,
        .bmAttributes =         USB_CONFIG_ATT_ONE | USB_CONFIG_ATT_SELFPOWER,
        .bMaxPower =            CONFIG_USB_GADGET_VBUS_DRAW / 2,
};


static struct usb_qualifier_descriptor
dev_qualifier = {
        .bLength =              sizeof dev_qualifier,
        .bDescriptorType =      USB_DT_DEVICE_QUALIFIER,

        .bcdUSB =               cpu_to_le16(0x0200),
        .bDeviceClass =         USB_CLASS_PER_INTERFACE,

        .bNumConfigurations =   1,
};



/*
 * Config descriptors must agree with the code that sets configurations
 * and with code managing interfaces and their altsettings.  They must
 * also handle different speeds and other-speed requests.
 */
static int populate_config_buf(struct usb_gadget *gadget,
                u8 *buf, u8 type, unsigned index)
{
        enum usb_device_speed                   speed = gadget->speed;
        int                                     len;
        const struct usb_descriptor_header      **function;

        if (index > 0)
                return -EINVAL;

        if (gadget_is_dualspeed(gadget) && type == USB_DT_OTHER_SPEED_CONFIG)
                speed = (USB_SPEED_FULL + USB_SPEED_HIGH) - speed;
        if (gadget_is_dualspeed(gadget) && speed == USB_SPEED_HIGH)
                function = fsg_hs_function;
        else
                function = fsg_fs_function;

        /* for now, don't advertise srp-only devices */
        if (!gadget_is_otg(gadget))
                function++;

        len = usb_gadget_config_buf(&config_desc, buf, EP0_BUFSIZE, function);
        ((struct usb_config_descriptor *) buf)->bDescriptorType = type;
        return len;
}


/*-------------------------------------------------------------------------*/

/* These routines may be called in process context or in_irq */

/* Caller must hold fsg->lock */
static void wakeup_thread(struct fsg_dev *fsg)
{
        /* Tell the main thread that something has happened */
        fsg->thread_wakeup_needed = 1;
        if (fsg->thread_task)
                wake_up_process(fsg->thread_task);
}


static void raise_exception(struct fsg_dev *fsg, enum fsg_state new_state)
{
        unsigned long           flags;

        /* Do nothing if a higher-priority exception is already in progress.
         * If a lower-or-equal priority exception is in progress, preempt it
         * and notify the main thread by sending it a signal. */
        spin_lock_irqsave(&fsg->lock, flags);
        if (fsg->state <= new_state) {
                fsg->exception_req_tag = fsg->ep0_req_tag;
                fsg->state = new_state;
                if (fsg->thread_task)
                        send_sig_info(SIGUSR1, SEND_SIG_FORCED,
                                        fsg->thread_task);
        }
        spin_unlock_irqrestore(&fsg->lock, flags);
}


/*-------------------------------------------------------------------------*/

/* The disconnect callback and ep0 routines.  These always run in_irq,
 * except that ep0_queue() is called in the main thread to acknowledge
 * completion of various requests: set config, set interface, and
 * Bulk-only device reset. */

static void fsg_disconnect(struct usb_gadget *gadget)
{
        struct fsg_dev          *fsg = get_gadget_data(gadget);

        DBG(fsg, "disconnect or port reset\n");
        raise_exception(fsg, FSG_STATE_DISCONNECT);
}


static int ep0_queue(struct fsg_dev *fsg)
{
        int     rc;

        rc = usb_ep_queue(fsg->ep0, fsg->ep0req, GFP_ATOMIC);
        if (rc != 0 && rc != -ESHUTDOWN) {

                /* We can't do much more than wait for a reset */
                WARNING(fsg, "error in submission: %s --> %d\n",
                                fsg->ep0->name, rc);
        }
        return rc;
}

static void ep0_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct fsg_dev          *fsg = ep->driver_data;

        if (req->actual > 0)
                dump_msg(fsg, fsg->ep0req_name, req->buf, req->actual);
        if (req->status || req->actual != req->length)
                DBG(fsg, "%s --> %d, %u/%u\n", __func__,
                                req->status, req->actual, req->length);
        if (req->status == -ECONNRESET)         // Request was cancelled
                usb_ep_fifo_flush(ep);

        if (req->status == 0 && req->context)
                ((fsg_routine_t) (req->context))(fsg);
}


/*-------------------------------------------------------------------------*/

/* Bulk and interrupt endpoint completion handlers.
 * These always run in_irq. */

static void bulk_in_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct fsg_dev          *fsg = ep->driver_data;
        struct fsg_buffhd       *bh = req->context;

        if (req->status || req->actual != req->length)
                DBG(fsg, "%s --> %d, %u/%u\n", __func__,
                                req->status, req->actual, req->length);
        if (req->status == -ECONNRESET)         // Request was cancelled
                usb_ep_fifo_flush(ep);

        /* Hold the lock while we update the request and buffer states */
        smp_wmb();
        spin_lock(&fsg->lock);
        bh->inreq_busy = 0;
        bh->state = BUF_STATE_EMPTY;
        wakeup_thread(fsg);
        spin_unlock(&fsg->lock);
}

static void bulk_out_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct fsg_dev          *fsg = ep->driver_data;
        struct fsg_buffhd       *bh = req->context;

        dump_msg(fsg, "bulk-out", req->buf, req->actual);
        if (req->status || req->actual != bh->bulk_out_intended_length)
                DBG(fsg, "%s --> %d, %u/%u\n", __func__,
                                req->status, req->actual,
                                bh->bulk_out_intended_length);
        if (req->status == -ECONNRESET)         // Request was cancelled
                usb_ep_fifo_flush(ep);

        /* Hold the lock while we update the request and buffer states */
        smp_wmb();
        spin_lock(&fsg->lock);
        bh->outreq_busy = 0;
        bh->state = BUF_STATE_FULL;
        wakeup_thread(fsg);
        spin_unlock(&fsg->lock);
}


/*-------------------------------------------------------------------------*/

/* Ep0 class-specific handlers.  These always run in_irq. */

static int class_setup_req(struct fsg_dev *fsg,
                const struct usb_ctrlrequest *ctrl)
{
        struct usb_request      *req = fsg->ep0req;
        u16                     w_index = le16_to_cpu(ctrl->wIndex);
        u16                     w_value = le16_to_cpu(ctrl->wValue);
        u16                     w_length = le16_to_cpu(ctrl->wLength);

        if (!fsg->config)
                return -EOPNOTSUPP;

        switch (ctrl->bRequest) {

        case USB_BULK_RESET_REQUEST:
                if (ctrl->bRequestType !=
                    (USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                        break;
                if (w_index != 0 || w_value != 0)
                        return -EDOM;

                /* Raise an exception to stop the current operation
                 * and reinitialize our state. */
                DBG(fsg, "bulk reset request\n");
                raise_exception(fsg, FSG_STATE_RESET);
                return DELAYED_STATUS;

        case USB_BULK_GET_MAX_LUN_REQUEST:
                if (ctrl->bRequestType !=
                    (USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                        break;
                if (w_index != 0 || w_value != 0)
                        return -EDOM;
                VDBG(fsg, "get max LUN\n");
                *(u8 *) req->buf = fsg->nluns - 1;
                return 1;
        }

        VDBG(fsg,
             "unknown class-specific control req "
             "%02x.%02x v%04x i%04x l%u\n",
             ctrl->bRequestType, ctrl->bRequest,
             le16_to_cpu(ctrl->wValue), w_index, w_length);
        return -EOPNOTSUPP;
}


/*-------------------------------------------------------------------------*/

/* Ep0 standard request handlers.  These always run in_irq. */

static int standard_setup_req(struct fsg_dev *fsg,
                const struct usb_ctrlrequest *ctrl)
{
        struct usb_request      *req = fsg->ep0req;
        int                     value = -EOPNOTSUPP;
        u16                     w_index = le16_to_cpu(ctrl->wIndex);
        u16                     w_value = le16_to_cpu(ctrl->wValue);

        /* Usually this just stores reply data in the pre-allocated ep0 buffer,
         * but config change events will also reconfigure hardware. */
        switch (ctrl->bRequest) {

        case USB_REQ_GET_DESCRIPTOR:
                if (ctrl->bRequestType != (USB_DIR_IN | USB_TYPE_STANDARD |
                                USB_RECIP_DEVICE))
                        break;
                switch (w_value >> 8) {

                case USB_DT_DEVICE:
                        VDBG(fsg, "get device descriptor\n");
                        value = sizeof device_desc;
                        memcpy(req->buf, &device_desc, value);
                        break;
                case USB_DT_DEVICE_QUALIFIER:
                        VDBG(fsg, "get device qualifier\n");
                        if (!gadget_is_dualspeed(fsg->gadget))
                                break;
                        value = sizeof dev_qualifier;
                        memcpy(req->buf, &dev_qualifier, value);
                        break;

                case USB_DT_OTHER_SPEED_CONFIG:
                        VDBG(fsg, "get other-speed config descriptor\n");
                        if (!gadget_is_dualspeed(fsg->gadget))
                                break;
                        goto get_config;
                case USB_DT_CONFIG:
                        VDBG(fsg, "get configuration descriptor\n");
get_config:
                        value = populate_config_buf(fsg->gadget,
                                        req->buf,
                                        w_value >> 8,
                                        w_value & 0xff);
                        break;

                case USB_DT_STRING:
                        VDBG(fsg, "get string descriptor\n");

                        /* wIndex == language code */
                        value = usb_gadget_get_string(&fsg_stringtab,
                                        w_value & 0xff, req->buf);
                        break;
                }
                break;

        /* One config, two speeds */
        case USB_REQ_SET_CONFIGURATION:
                if (ctrl->bRequestType != (USB_DIR_OUT | USB_TYPE_STANDARD |
                                USB_RECIP_DEVICE))
                        break;
                VDBG(fsg, "set configuration\n");
                if (w_value == CONFIG_VALUE || w_value == 0) {
                        fsg->new_config = w_value;

                        /* Raise an exception to wipe out previous transaction
                         * state (queued bufs, etc) and set the new config. */
                        raise_exception(fsg, FSG_STATE_CONFIG_CHANGE);
                        value = DELAYED_STATUS;
                }
                break;
        case USB_REQ_GET_CONFIGURATION:
                if (ctrl->bRequestType != (USB_DIR_IN | USB_TYPE_STANDARD |
                                USB_RECIP_DEVICE))
                        break;
                VDBG(fsg, "get configuration\n");
                *(u8 *) req->buf = fsg->config;
                value = 1;
                break;

        case USB_REQ_SET_INTERFACE:
                if (ctrl->bRequestType != (USB_DIR_OUT| USB_TYPE_STANDARD |
                                USB_RECIP_INTERFACE))
                        break;
                if (fsg->config && w_index == 0) {

                        /* Raise an exception to wipe out previous transaction
                         * state (queued bufs, etc) and install the new
                         * interface altsetting. */
                        raise_exception(fsg, FSG_STATE_INTERFACE_CHANGE);
                        value = DELAYED_STATUS;
                }
                break;
        case USB_REQ_GET_INTERFACE:
                if (ctrl->bRequestType != (USB_DIR_IN | USB_TYPE_STANDARD |
                                USB_RECIP_INTERFACE))
                        break;
                if (!fsg->config)
                        break;
                if (w_index != 0) {
                        value = -EDOM;
                        break;
                }
                VDBG(fsg, "get interface\n");
                *(u8 *) req->buf = 0;
                value = 1;
                break;

        default:
                VDBG(fsg,
                        "unknown control req %02x.%02x v%04x i%04x l%u\n",
                        ctrl->bRequestType, ctrl->bRequest,
                        w_value, w_index, le16_to_cpu(ctrl->wLength));
        }

        return value;
}


static int fsg_setup(struct usb_gadget *gadget,
                const struct usb_ctrlrequest *ctrl)
{
        struct fsg_dev          *fsg = get_gadget_data(gadget);
        int                     rc;
        int                     w_length = le16_to_cpu(ctrl->wLength);

        ++fsg->ep0_req_tag;             // Record arrival of a new request
        fsg->ep0req->context = NULL;
        fsg->ep0req->length = 0;
        dump_msg(fsg, "ep0-setup", (u8 *) ctrl, sizeof(*ctrl));

        if ((ctrl->bRequestType & USB_TYPE_MASK) == USB_TYPE_CLASS)
                rc = class_setup_req(fsg, ctrl);
        else
                rc = standard_setup_req(fsg, ctrl);

        /* Respond with data/status or defer until later? */
        if (rc >= 0 && rc != DELAYED_STATUS) {
                rc = min(rc, w_length);
                fsg->ep0req->length = rc;
                fsg->ep0req->zero = rc < w_length;
                fsg->ep0req_name = (ctrl->bRequestType & USB_DIR_IN ?
                                "ep0-in" : "ep0-out");
                rc = ep0_queue(fsg);
        }

        /* Device either stalls (rc < 0) or reports success */
        return rc;
}


/*-------------------------------------------------------------------------*/

/* All the following routines run in process context */


/* Use this for bulk or interrupt transfers, not ep0 */
static void start_transfer(struct fsg_dev *fsg, struct usb_ep *ep,
                struct usb_request *req, int *pbusy,
                enum fsg_buffer_state *state)
{
        int     rc;

        if (ep == fsg->bulk_in)
                dump_msg(fsg, "bulk-in", req->buf, req->length);

        spin_lock_irq(&fsg->lock);
        *pbusy = 1;
        *state = BUF_STATE_BUSY;
        spin_unlock_irq(&fsg->lock);
        rc = usb_ep_queue(ep, req, GFP_KERNEL);
        if (rc != 0) {
                *pbusy = 0;
                *state = BUF_STATE_EMPTY;

                /* We can't do much more than wait for a reset */

                /* Note: currently the net2280 driver fails zero-length
                 * submissions if DMA is enabled. */
                if (rc != -ESHUTDOWN && !(rc == -EOPNOTSUPP &&
                                                req->length == 0))
                        WARNING(fsg, "error in submission: %s --> %d\n",
                                        ep->name, rc);
        }
}


static int sleep_thread(struct fsg_dev *fsg)
{
        int     rc = 0;

        /* Wait until a signal arrives or we are woken up */
        for (;;) {
                try_to_freeze();
                set_current_state(TASK_INTERRUPTIBLE);
                if (signal_pending(current)) {
                        rc = -EINTR;
                        break;
                }
                if (fsg->thread_wakeup_needed)
                        break;
                schedule();
        }
        __set_current_state(TASK_RUNNING);
        fsg->thread_wakeup_needed = 0;
        return rc;
}


/*-------------------------------------------------------------------------*/

static int do_read(struct fsg_dev *fsg)
{
        struct fsg_lun          *curlun = fsg->curlun;
        u32                     lba;
        struct fsg_buffhd       *bh;
        int                     rc;
        u32                     amount_left;
        loff_t                  file_offset, file_offset_tmp;
        unsigned int            amount;
        unsigned int            partial_page;
        ssize_t                 nread;

        /* Get the starting Logical Block Address and check that it's
         * not too big */
        if (fsg->cmnd[0] == SC_READ_6)
                lba = get_unaligned_be24(&fsg->cmnd[1]);
        else {
                lba = get_unaligned_be32(&fsg->cmnd[2]);

                /* We allow DPO (Disable Page Out = don't save data in the
                 * cache) and FUA (Force Unit Access = don't read from the
                 * cache), but we don't implement them. */
                if ((fsg->cmnd[1] & ~0x18) != 0) {
                        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
        }
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }
        file_offset = ((loff_t) lba) << 9;

        /* Carry out the file reads */
        amount_left = fsg->data_size_from_cmnd;
        if (unlikely(amount_left == 0))
                return -EIO;            // No default reply

        for (;;) {

                /* Figure out how much we need to read:
                 * Try to read the remaining amount.
                 * But don't read more than the buffer size.
                 * And don't try to read past the end of the file.
                 * Finally, if we're not at a page boundary, don't read past
                 *      the next page.
                 * If this means reading 0 then we were asked to read past
                 *      the end of file. */
                amount = min(amount_left, FSG_BUFLEN);
                amount = min((loff_t) amount,
                                curlun->file_length - file_offset);
                partial_page = file_offset & (PAGE_CACHE_SIZE - 1);
                if (partial_page > 0)
                        amount = min(amount, (unsigned int) PAGE_CACHE_SIZE -
                                        partial_page);

                /* Wait for the next buffer to become available */
                bh = fsg->next_buffhd_to_fill;
                while (bh->state != BUF_STATE_EMPTY) {
                        rc = sleep_thread(fsg);
                        if (rc)
                                return rc;
                }

                /* If we were asked to read past the end of file,
                 * end with an empty buffer. */
                if (amount == 0) {
                        curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                        curlun->sense_data_info = file_offset >> 9;
                        curlun->info_valid = 1;
                        bh->inreq->length = 0;
                        bh->state = BUF_STATE_FULL;
                        break;
                }

                /* Perform the read */
                file_offset_tmp = file_offset;
                nread = vfs_read(curlun->filp,
                                (char __user *) bh->buf,
                                amount, &file_offset_tmp);
                VLDBG(curlun, "file read %u @ %llu -> %d\n", amount,
                                (unsigned long long) file_offset,
                                (int) nread);
                if (signal_pending(current))
                        return -EINTR;

                if (nread < 0) {
                        LDBG(curlun, "error in file read: %d\n",
                                        (int) nread);
                        nread = 0;
                } else if (nread < amount) {
                        LDBG(curlun, "partial file read: %d/%u\n",
                                        (int) nread, amount);
                        nread -= (nread & 511); // Round down to a block
                }
                file_offset  += nread;
                amount_left  -= nread;
                fsg->residue -= nread;
                bh->inreq->length = nread;
                bh->state = BUF_STATE_FULL;

                /* If an error occurred, report it and its position */
                if (nread < amount) {
                        curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
                        curlun->sense_data_info = file_offset >> 9;
                        curlun->info_valid = 1;
                        break;
                }

                if (amount_left == 0)
                        break;          // No more left to read

                /* Send this buffer and go read some more */
                bh->inreq->zero = 0;
                start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                &bh->inreq_busy, &bh->state);
                fsg->next_buffhd_to_fill = bh->next;
        }

        return -EIO;            // No default reply
}


/*-------------------------------------------------------------------------*/

static int do_write(struct fsg_dev *fsg)
{
        struct fsg_lun          *curlun = fsg->curlun;
        u32                     lba;
        struct fsg_buffhd       *bh;
        int                     get_some_more;
        u32                     amount_left_to_req, amount_left_to_write;
        loff_t                  usb_offset, file_offset, file_offset_tmp;
        unsigned int            amount;
        unsigned int            partial_page;
        ssize_t                 nwritten;
        int                     rc;

        if (curlun->ro) {
                curlun->sense_data = SS_WRITE_PROTECTED;
                return -EINVAL;
        }
        spin_lock(&curlun->filp->f_lock);
        curlun->filp->f_flags &= ~O_SYNC;       // Default is not to wait
        spin_unlock(&curlun->filp->f_lock);

        /* Get the starting Logical Block Address and check that it's
         * not too big */
        if (fsg->cmnd[0] == SC_WRITE_6)
                lba = get_unaligned_be24(&fsg->cmnd[1]);
        else {
                lba = get_unaligned_be32(&fsg->cmnd[2]);

                /* We allow DPO (Disable Page Out = don't save data in the
                 * cache) and FUA (Force Unit Access = write directly to the
                 * medium).  We don't implement DPO; we implement FUA by
                 * performing synchronous output. */
                if ((fsg->cmnd[1] & ~0x18) != 0) {
                        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
                if (fsg->cmnd[1] & 0x08) {      // FUA
                        spin_lock(&curlun->filp->f_lock);
                        curlun->filp->f_flags |= O_SYNC;
                        spin_unlock(&curlun->filp->f_lock);
                }
        }
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }

        /* Carry out the file writes */
        get_some_more = 1;
        file_offset = usb_offset = ((loff_t) lba) << 9;
        amount_left_to_req = amount_left_to_write = fsg->data_size_from_cmnd;

        while (amount_left_to_write > 0) {

                /* Queue a request for more data from the host */
                bh = fsg->next_buffhd_to_fill;
                if (bh->state == BUF_STATE_EMPTY && get_some_more) {

                        /* Figure out how much we want to get:
                         * Try to get the remaining amount.
                         * But don't get more than the buffer size.
                         * And don't try to go past the end of the file.
                         * If we're not at a page boundary,
                         *      don't go past the next page.
                         * If this means getting 0, then we were asked
                         *      to write past the end of file.
                         * Finally, round down to a block boundary. */
                        amount = min(amount_left_to_req, FSG_BUFLEN);
                        amount = min((loff_t) amount, curlun->file_length -
                                        usb_offset);
                        partial_page = usb_offset & (PAGE_CACHE_SIZE - 1);
                        if (partial_page > 0)
                                amount = min(amount,
        (unsigned int) PAGE_CACHE_SIZE - partial_page);

                        if (amount == 0) {
                                get_some_more = 0;
                                curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                                curlun->sense_data_info = usb_offset >> 9;
                                curlun->info_valid = 1;
                                continue;
                        }
                        amount -= (amount & 511);
                        if (amount == 0) {

                                /* Why were we were asked to transfer a
                                 * partial block? */
                                get_some_more = 0;
                                continue;
                        }

                        /* Get the next buffer */
                        usb_offset += amount;
                        fsg->usb_amount_left -= amount;
                        amount_left_to_req -= amount;
                        if (amount_left_to_req == 0)
                                get_some_more = 0;

                        /* amount is always divisible by 512, hence by
                         * the bulk-out maxpacket size */
                        bh->outreq->length = bh->bulk_out_intended_length =
                                        amount;
                        bh->outreq->short_not_ok = 1;
                        start_transfer(fsg, fsg->bulk_out, bh->outreq,
                                        &bh->outreq_busy, &bh->state);
                        fsg->next_buffhd_to_fill = bh->next;
                        continue;
                }

                /* Write the received data to the backing file */
                bh = fsg->next_buffhd_to_drain;
                if (bh->state == BUF_STATE_EMPTY && !get_some_more)
                        break;                  // We stopped early
                if (bh->state == BUF_STATE_FULL) {
                        smp_rmb();
                        fsg->next_buffhd_to_drain = bh->next;
                        bh->state = BUF_STATE_EMPTY;

                        /* Did something go wrong with the transfer? */
                        if (bh->outreq->status != 0) {
                                curlun->sense_data = SS_COMMUNICATION_FAILURE;
                                curlun->sense_data_info = file_offset >> 9;
                                curlun->info_valid = 1;
                                break;
                        }

                        amount = bh->outreq->actual;
                        if (curlun->file_length - file_offset < amount) {
                                LERROR(curlun,
        "write %u @ %llu beyond end %llu\n",
        amount, (unsigned long long) file_offset,
        (unsigned long long) curlun->file_length);
                                amount = curlun->file_length - file_offset;
                        }

                        /* Perform the write */
                        file_offset_tmp = file_offset;
                        nwritten = vfs_write(curlun->filp,
                                        (char __user *) bh->buf,
                                        amount, &file_offset_tmp);
                        VLDBG(curlun, "file write %u @ %llu -> %d\n", amount,
                                        (unsigned long long) file_offset,
                                        (int) nwritten);
                        if (signal_pending(current))
                                return -EINTR;          // Interrupted!

                        if (nwritten < 0) {
                                LDBG(curlun, "error in file write: %d\n",
                                                (int) nwritten);
                                nwritten = 0;
                        } else if (nwritten < amount) {
                                LDBG(curlun, "partial file write: %d/%u\n",
                                                (int) nwritten, amount);
                                nwritten -= (nwritten & 511);
                                                // Round down to a block
                        }
                        file_offset += nwritten;
                        amount_left_to_write -= nwritten;
                        fsg->residue -= nwritten;

                        /* If an error occurred, report it and its position */
                        if (nwritten < amount) {
                                curlun->sense_data = SS_WRITE_ERROR;
                                curlun->sense_data_info = file_offset >> 9;
                                curlun->info_valid = 1;
                                break;
                        }

                        /* Did the host decide to stop early? */
                        if (bh->outreq->actual != bh->outreq->length) {
                                fsg->short_packet_received = 1;
                                break;
                        }
                        continue;
                }

                /* Wait for something to happen */
                rc = sleep_thread(fsg);
                if (rc)
                        return rc;
        }

        return -EIO;            // No default reply
}


/*-------------------------------------------------------------------------*/

static int do_synchronize_cache(struct fsg_dev *fsg)
{
        struct fsg_lun  *curlun = fsg->curlun;
        int             rc;

        /* We ignore the requested LBA and write out all file's
         * dirty data buffers. */
        rc = fsg_lun_fsync_sub(curlun);
        if (rc)
                curlun->sense_data = SS_WRITE_ERROR;
        return 0;
}


/*-------------------------------------------------------------------------*/

static void invalidate_sub(struct fsg_lun *curlun)
{
        struct file     *filp = curlun->filp;
        struct inode    *inode = filp->f_path.dentry->d_inode;
        unsigned long   rc;

        rc = invalidate_mapping_pages(inode->i_mapping, 0, -1);
        VLDBG(curlun, "invalidate_inode_pages -> %ld\n", rc);
}

static int do_verify(struct fsg_dev *fsg)
{
        struct fsg_lun          *curlun = fsg->curlun;
        u32                     lba;
        u32                     verification_length;
        struct fsg_buffhd       *bh = fsg->next_buffhd_to_fill;
        loff_t                  file_offset, file_offset_tmp;
        u32                     amount_left;
        unsigned int            amount;
        ssize_t                 nread;

        /* Get the starting Logical Block Address and check that it's
         * not too big */
        lba = get_unaligned_be32(&fsg->cmnd[2]);
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }

        /* We allow DPO (Disable Page Out = don't save data in the
         * cache) but we don't implement it. */
        if ((fsg->cmnd[1] & ~0x10) != 0) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        verification_length = get_unaligned_be16(&fsg->cmnd[7]);
        if (unlikely(verification_length == 0))
                return -EIO;            // No default reply

        /* Prepare to carry out the file verify */
        amount_left = verification_length << 9;
        file_offset = ((loff_t) lba) << 9;

        /* Write out all the dirty buffers before invalidating them */
        fsg_lun_fsync_sub(curlun);
        if (signal_pending(current))
                return -EINTR;

        invalidate_sub(curlun);
        if (signal_pending(current))
                return -EINTR;

        /* Just try to read the requested blocks */
        while (amount_left > 0) {

                /* Figure out how much we need to read:
                 * Try to read the remaining amount, but not more than
                 * the buffer size.
                 * And don't try to read past the end of the file.
                 * If this means reading 0 then we were asked to read
                 * past the end of file. */
                amount = min(amount_left, FSG_BUFLEN);
                amount = min((loff_t) amount,
                                curlun->file_length - file_offset);
                if (amount == 0) {
                        curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                        curlun->sense_data_info = file_offset >> 9;
                        curlun->info_valid = 1;
                        break;
                }

                /* Perform the read */
                file_offset_tmp = file_offset;
                nread = vfs_read(curlun->filp,
                                (char __user *) bh->buf,
                                amount, &file_offset_tmp);
                VLDBG(curlun, "file read %u @ %llu -> %d\n", amount,
                                (unsigned long long) file_offset,
                                (int) nread);
                if (signal_pending(current))
                        return -EINTR;

                if (nread < 0) {
                        LDBG(curlun, "error in file verify: %d\n",
                                        (int) nread);
                        nread = 0;
                } else if (nread < amount) {
                        LDBG(curlun, "partial file verify: %d/%u\n",
                                        (int) nread, amount);
                        nread -= (nread & 511); // Round down to a sector
                }
                if (nread == 0) {
                        curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
                        curlun->sense_data_info = file_offset >> 9;
                        curlun->info_valid = 1;
                        break;
                }
                file_offset += nread;
                amount_left -= nread;
        }
        return 0;
}


/*-------------------------------------------------------------------------*/

static int do_inquiry(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        u8      *buf = (u8 *) bh->buf;

        static char vendor_id[] = "Linux   ";
        static char product_disk_id[] = "File-Stor Gadget";
        static char product_cdrom_id[] = "File-CD Gadget  ";

        if (!fsg->curlun) {             // Unsupported LUNs are okay
                fsg->bad_lun_okay = 1;
                memset(buf, 0, 36);
                buf[0] = 0x7f;          // Unsupported, no device-type
                buf[4] = 31;            // Additional length
                return 36;
        }

        memset(buf, 0, 8);
        buf[0] = (mod_data.cdrom ? TYPE_CDROM : TYPE_DISK);
        if (mod_data.removable)
                buf[1] = 0x80;
        buf[2] = 2;             // ANSI SCSI level 2
        buf[3] = 2;             // SCSI-2 INQUIRY data format
        buf[4] = 31;            // Additional length
                                // No special options
        sprintf(buf + 8, "%-8s%-16s%04x", vendor_id,
                        (mod_data.cdrom ? product_cdrom_id :
                                product_disk_id),
                        mod_data.release);
        return 36;
}


static int do_request_sense(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = fsg->curlun;
        u8              *buf = (u8 *) bh->buf;
        u32             sd, sdinfo;
        int             valid;

        /*
         * From the SCSI-2 spec., section 7.9 (Unit attention condition):
         *
         * If a REQUEST SENSE command is received from an initiator
         * with a pending unit attention condition (before the target
         * generates the contingent allegiance condition), then the
         * target shall either:
         *   a) report any pending sense data and preserve the unit
         *      attention condition on the logical unit, or,
         *   b) report the unit attention condition, may discard any
         *      pending sense data, and clear the unit attention
         *      condition on the logical unit for that initiator.
         *
         * FSG normally uses option a); enable this code to use option b).
         */
#if 0
        if (curlun && curlun->unit_attention_data != SS_NO_SENSE) {
                curlun->sense_data = curlun->unit_attention_data;
                curlun->unit_attention_data = SS_NO_SENSE;
        }
#endif

        if (!curlun) {          // Unsupported LUNs are okay
                fsg->bad_lun_okay = 1;
                sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;
                sdinfo = 0;
                valid = 0;
        } else {
                sd = curlun->sense_data;
                sdinfo = curlun->sense_data_info;
                valid = curlun->info_valid << 7;
                curlun->sense_data = SS_NO_SENSE;
                curlun->sense_data_info = 0;
                curlun->info_valid = 0;
        }

        memset(buf, 0, 18);
        buf[0] = valid | 0x70;                  // Valid, current error
        buf[2] = SK(sd);
        put_unaligned_be32(sdinfo, &buf[3]);    /* Sense information */
        buf[7] = 18 - 8;                        // Additional sense length
        buf[12] = ASC(sd);
        buf[13] = ASCQ(sd);
        return 18;
}


static int do_read_capacity(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = fsg->curlun;
        u32             lba = get_unaligned_be32(&fsg->cmnd[2]);
        int             pmi = fsg->cmnd[8];
        u8              *buf = (u8 *) bh->buf;

        /* Check the PMI and LBA fields */
        if (pmi > 1 || (pmi == 0 && lba != 0)) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        put_unaligned_be32(curlun->num_sectors - 1, &buf[0]);
                                                /* Max logical block */
        put_unaligned_be32(512, &buf[4]);       /* Block length */
        return 8;
}


static int do_read_header(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = fsg->curlun;
        int             msf = fsg->cmnd[1] & 0x02;
        u32             lba = get_unaligned_be32(&fsg->cmnd[2]);
        u8              *buf = (u8 *) bh->buf;

        if ((fsg->cmnd[1] & ~0x02) != 0) {              /* Mask away MSF */
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }

        memset(buf, 0, 8);
        buf[0] = 0x01;          /* 2048 bytes of user data, rest is EC */
        store_cdrom_address(&buf[4], msf, lba);
        return 8;
}


static int do_read_toc(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = fsg->curlun;
        int             msf = fsg->cmnd[1] & 0x02;
        int             start_track = fsg->cmnd[6];
        u8              *buf = (u8 *) bh->buf;

        if ((fsg->cmnd[1] & ~0x02) != 0 ||              /* Mask away MSF */
                        start_track > 1) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        memset(buf, 0, 20);
        buf[1] = (20-2);                /* TOC data length */
        buf[2] = 1;                     /* First track number */
        buf[3] = 1;                     /* Last track number */
        buf[5] = 0x16;                  /* Data track, copying allowed */
        buf[6] = 0x01;                  /* Only track is number 1 */
        store_cdrom_address(&buf[8], msf, 0);

        buf[13] = 0x16;                 /* Lead-out track is data */
        buf[14] = 0xAA;                 /* Lead-out track number */
        store_cdrom_address(&buf[16], msf, curlun->num_sectors);
        return 20;
}


static int do_mode_sense(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = fsg->curlun;
        int             mscmnd = fsg->cmnd[0];
        u8              *buf = (u8 *) bh->buf;
        u8              *buf0 = buf;
        int             pc, page_code;
        int             changeable_values, all_pages;
        int             valid_page = 0;
        int             len, limit;

        if ((fsg->cmnd[1] & ~0x08) != 0) {              // Mask away DBD
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }
        pc = fsg->cmnd[2] >> 6;
        page_code = fsg->cmnd[2] & 0x3f;
        if (pc == 3) {
                curlun->sense_data = SS_SAVING_PARAMETERS_NOT_SUPPORTED;
                return -EINVAL;
        }
        changeable_values = (pc == 1);
        all_pages = (page_code == 0x3f);

        /* Write the mode parameter header.  Fixed values are: default
         * medium type, no cache control (DPOFUA), and no block descriptors.
         * The only variable value is the WriteProtect bit.  We will fill in
         * the mode data length later. */
        memset(buf, 0, 8);
        if (mscmnd == SC_MODE_SENSE_6) {
                buf[2] = (curlun->ro ? 0x80 : 0x00);            // WP, DPOFUA
                buf += 4;
                limit = 255;
        } else {                        // SC_MODE_SENSE_10
                buf[3] = (curlun->ro ? 0x80 : 0x00);            // WP, DPOFUA
                buf += 8;
                limit = 65535;          // Should really be FSG_BUFLEN
        }

        /* No block descriptors */

        /* The mode pages, in numerical order.  The only page we support
         * is the Caching page. */
        if (page_code == 0x08 || all_pages) {
                valid_page = 1;
                buf[0] = 0x08;          // Page code
                buf[1] = 10;            // Page length
                memset(buf+2, 0, 10);   // None of the fields are changeable

                if (!changeable_values) {
                        buf[2] = 0x04;  // Write cache enable,
                                        // Read cache not disabled
                                        // No cache retention priorities
                        put_unaligned_be16(0xffff, &buf[4]);
                                        /* Don't disable prefetch */
                                        /* Minimum prefetch = 0 */
                        put_unaligned_be16(0xffff, &buf[8]);
                                        /* Maximum prefetch */
                        put_unaligned_be16(0xffff, &buf[10]);
                                        /* Maximum prefetch ceiling */
                }
                buf += 12;
        }

        /* Check that a valid page was requested and the mode data length
         * isn't too long. */
        len = buf - buf0;
        if (!valid_page || len > limit) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        /*  Store the mode data length */
        if (mscmnd == SC_MODE_SENSE_6)
                buf0[0] = len - 1;
        else
                put_unaligned_be16(len - 2, buf0);
        return len;
}


static int do_start_stop(struct fsg_dev *fsg)
{
        if (!mod_data.removable) {
                fsg->curlun->sense_data = SS_INVALID_COMMAND;
                return -EINVAL;
        }
        return 0;
}


static int do_prevent_allow(struct fsg_dev *fsg)
{
        struct fsg_lun  *curlun = fsg->curlun;
        int             prevent;

        if (!mod_data.removable) {
                curlun->sense_data = SS_INVALID_COMMAND;
                return -EINVAL;
        }

        prevent = fsg->cmnd[4] & 0x01;
        if ((fsg->cmnd[4] & ~0x01) != 0) {              // Mask away Prevent
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        if (curlun->prevent_medium_removal && !prevent)
                fsg_lun_fsync_sub(curlun);
        curlun->prevent_medium_removal = prevent;
        return 0;
}


static int do_read_format_capacities(struct fsg_dev *fsg,
                        struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = fsg->curlun;
        u8              *buf = (u8 *) bh->buf;

        buf[0] = buf[1] = buf[2] = 0;
        buf[3] = 8;             // Only the Current/Maximum Capacity Descriptor
        buf += 4;

        put_unaligned_be32(curlun->num_sectors, &buf[0]);
                                                /* Number of blocks */
        put_unaligned_be32(512, &buf[4]);       /* Block length */
        buf[4] = 0x02;                          /* Current capacity */
        return 12;
}


static int do_mode_select(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = fsg->curlun;

        /* We don't support MODE SELECT */
        curlun->sense_data = SS_INVALID_COMMAND;
        return -EINVAL;
}


/*-------------------------------------------------------------------------*/

static int halt_bulk_in_endpoint(struct fsg_dev *fsg)
{
        int     rc;

        rc = fsg_set_halt(fsg, fsg->bulk_in);
        if (rc == -EAGAIN)
                VDBG(fsg, "delayed bulk-in endpoint halt\n");
        while (rc != 0) {
                if (rc != -EAGAIN) {
                        WARNING(fsg, "usb_ep_set_halt -> %d\n", rc);
                        rc = 0;
                        break;
                }

                /* Wait for a short time and then try again */
                if (msleep_interruptible(100) != 0)
                        return -EINTR;
                rc = usb_ep_set_halt(fsg->bulk_in);
        }
        return rc;
}

static int wedge_bulk_in_endpoint(struct fsg_dev *fsg)
{
        int     rc;

        DBG(fsg, "bulk-in set wedge\n");
        rc = usb_ep_set_wedge(fsg->bulk_in);
        if (rc == -EAGAIN)
                VDBG(fsg, "delayed bulk-in endpoint wedge\n");
        while (rc != 0) {
                if (rc != -EAGAIN) {
                        WARNING(fsg, "usb_ep_set_wedge -> %d\n", rc);
                        rc = 0;
                        break;
                }

                /* Wait for a short time and then try again */
                if (msleep_interruptible(100) != 0)
                        return -EINTR;
                rc = usb_ep_set_wedge(fsg->bulk_in);
        }
        return rc;
}

static int pad_with_zeros(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh = fsg->next_buffhd_to_fill;
        u32                     nkeep = bh->inreq->length;
        u32                     nsend;
        int                     rc;

        bh->state = BUF_STATE_EMPTY;            // For the first iteration
        fsg->usb_amount_left = nkeep + fsg->residue;
        while (fsg->usb_amount_left > 0) {

                /* Wait for the next buffer to be free */
                while (bh->state != BUF_STATE_EMPTY) {
                        rc = sleep_thread(fsg);
                        if (rc)
                                return rc;
                }

                nsend = min(fsg->usb_amount_left, FSG_BUFLEN);
                memset(bh->buf + nkeep, 0, nsend - nkeep);
                bh->inreq->length = nsend;
                bh->inreq->zero = 0;
                start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                &bh->inreq_busy, &bh->state);
                bh = fsg->next_buffhd_to_fill = bh->next;
                fsg->usb_amount_left -= nsend;
                nkeep = 0;
        }
        return 0;
}

static int throw_away_data(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh;
        u32                     amount;
        int                     rc;

        while ((bh = fsg->next_buffhd_to_drain)->state != BUF_STATE_EMPTY ||
                        fsg->usb_amount_left > 0) {

                /* Throw away the data in a filled buffer */
                if (bh->state == BUF_STATE_FULL) {
                        smp_rmb();
                        bh->state = BUF_STATE_EMPTY;
                        fsg->next_buffhd_to_drain = bh->next;

                        /* A short packet or an error ends everything */
                        if (bh->outreq->actual != bh->outreq->length ||
                                        bh->outreq->status != 0) {
                                raise_exception(fsg, FSG_STATE_ABORT_BULK_OUT);
                                return -EINTR;
                        }
                        continue;
                }

                /* Try to submit another request if we need one */
                bh = fsg->next_buffhd_to_fill;
                if (bh->state == BUF_STATE_EMPTY && fsg->usb_amount_left > 0) {
                        amount = min(fsg->usb_amount_left, FSG_BUFLEN);

                        /* amount is always divisible by 512, hence by
                         * the bulk-out maxpacket size */
                        bh->outreq->length = bh->bulk_out_intended_length =
                                        amount;
                        bh->outreq->short_not_ok = 1;
                        start_transfer(fsg, fsg->bulk_out, bh->outreq,
                                        &bh->outreq_busy, &bh->state);
                        fsg->next_buffhd_to_fill = bh->next;
                        fsg->usb_amount_left -= amount;
                        continue;
                }

                /* Otherwise wait for something to happen */
                rc = sleep_thread(fsg);
                if (rc)
                        return rc;
        }
        return 0;
}


static int finish_reply(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh = fsg->next_buffhd_to_fill;
        int                     rc = 0;

        switch (fsg->data_dir) {
        case DATA_DIR_NONE:
                break;                  // Nothing to send

        /* If we don't know whether the host wants to read or write,
         * this must be CB or CBI with an unknown command.  We mustn't
         * try to send or receive any data.  So stall both bulk pipes
         * if we can and wait for a reset. */
        case DATA_DIR_UNKNOWN:
                if (mod_data.can_stall) {
                        fsg_set_halt(fsg, fsg->bulk_out);
                        rc = halt_bulk_in_endpoint(fsg);
                }
                break;

        /* All but the last buffer of data must have already been sent */
        case DATA_DIR_TO_HOST:
                if (fsg->data_size == 0) {
                        /* Nothing to send */

                /* If there's no residue, simply send the last buffer */
                } else if (fsg->residue == 0) {
                        bh->inreq->zero = 0;
                        start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                        &bh->inreq_busy, &bh->state);
                        fsg->next_buffhd_to_fill = bh->next;

                /* For Bulk-only, if we're allowed to stall then send the
                 * short packet and halt the bulk-in endpoint.  If we can't
                 * stall, pad out the remaining data with 0's. */
                } else if (mod_data.can_stall) {
                        bh->inreq->zero = 1;
                        start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                       &bh->inreq_busy, &bh->state);
                        fsg->next_buffhd_to_fill = bh->next;
                        rc = halt_bulk_in_endpoint(fsg);
                } else {
                        rc = pad_with_zeros(fsg);
                }
                break;

        /* We have processed all we want from the data the host has sent.
         * There may still be outstanding bulk-out requests. */
        case DATA_DIR_FROM_HOST:
                if (fsg->residue == 0)
                        ;               // Nothing to receive

                /* Did the host stop sending unexpectedly early? */
                else if (fsg->short_packet_received) {
                        raise_exception(fsg, FSG_STATE_ABORT_BULK_OUT);
                        rc = -EINTR;
                }

                /* We haven't processed all the incoming data.  Even though
                 * we may be allowed to stall, doing so would cause a race.
                 * The controller may already have ACK'ed all the remaining
                 * bulk-out packets, in which case the host wouldn't see a
                 * STALL.  Not realizing the endpoint was halted, it wouldn't
                 * clear the halt -- leading to problems later on. */
#if 0
                else if (mod_data.can_stall) {
                        fsg_set_halt(fsg, fsg->bulk_out);
                        raise_exception(fsg, FSG_STATE_ABORT_BULK_OUT);
                        rc = -EINTR;
                }
#endif

                /* We can't stall.  Read in the excess data and throw it
                 * all away. */
                else
                        rc = throw_away_data(fsg);
                break;
        }
        return rc;
}


static int send_status(struct fsg_dev *fsg)
{
        struct fsg_lun          *curlun = fsg->curlun;
        struct fsg_buffhd       *bh;
        struct bulk_cs_wrap     *csw;
        int                     rc;
        u8                      status = USB_STATUS_PASS;
        u32                     sd, sdinfo = 0;

        /* Wait for the next buffer to become available */
        bh = fsg->next_buffhd_to_fill;
        while (bh->state != BUF_STATE_EMPTY) {
                rc = sleep_thread(fsg);
                if (rc)
                        return rc;
        }

        if (curlun) {
                sd = curlun->sense_data;
                sdinfo = curlun->sense_data_info;
        } else if (fsg->bad_lun_okay)
                sd = SS_NO_SENSE;
        else
                sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;

        if (fsg->phase_error) {
                DBG(fsg, "sending phase-error status\n");
                status = USB_STATUS_PHASE_ERROR;
                sd = SS_INVALID_COMMAND;
        } else if (sd != SS_NO_SENSE) {
                DBG(fsg, "sending command-failure status\n");
                status = USB_STATUS_FAIL;
                VDBG(fsg, "  sense data: SK x%02x, ASC x%02x, ASCQ x%02x;"
                                "  info x%x\n",
                                SK(sd), ASC(sd), ASCQ(sd), sdinfo);
        }


        /* Store and send the Bulk-only CSW */
        csw = bh->buf;

        csw->Signature = cpu_to_le32(USB_BULK_CS_SIG);
        csw->Tag = fsg->tag;
        csw->Residue = cpu_to_le32(fsg->residue);
        csw->Status = status;

        bh->inreq->length = USB_BULK_CS_WRAP_LEN;
        bh->inreq->zero = 0;
        start_transfer(fsg, fsg->bulk_in, bh->inreq,
                       &bh->inreq_busy, &bh->state);

        fsg->next_buffhd_to_fill = bh->next;
        return 0;
}


/*-------------------------------------------------------------------------*/

/* Check whether the command is properly formed and whether its data size
 * and direction agree with the values we already have. */
static int check_command(struct fsg_dev *fsg, int cmnd_size,
                enum data_direction data_dir, unsigned int mask,
                int needs_medium, const char *name)
{
        int                     i;
        int                     lun = fsg->cmnd[1] >> 5;
        static const char       dirletter[4] = {'u', 'o', 'i', 'n'};
        char                    hdlen[20];
        struct fsg_lun          *curlun;

        hdlen[0] = 0;
        if (fsg->data_dir != DATA_DIR_UNKNOWN)
                sprintf(hdlen, ", H%c=%u", dirletter[(int) fsg->data_dir],
                                fsg->data_size);
        VDBG(fsg, "SCSI command: %s;  Dc=%d, D%c=%u;  Hc=%d%s\n",
                        name, cmnd_size, dirletter[(int) data_dir],
                        fsg->data_size_from_cmnd, fsg->cmnd_size, hdlen);

        /* We can't reply at all until we know the correct data direction
         * and size. */
        if (fsg->data_size_from_cmnd == 0)
                data_dir = DATA_DIR_NONE;
        if (fsg->data_dir == DATA_DIR_UNKNOWN) {        // CB or CBI
                fsg->data_dir = data_dir;
                fsg->data_size = fsg->data_size_from_cmnd;

        } else {                                        // Bulk-only
                if (fsg->data_size < fsg->data_size_from_cmnd) {

                        /* Host data size < Device data size is a phase error.
                         * Carry out the command, but only transfer as much
                         * as we are allowed. */
                        fsg->data_size_from_cmnd = fsg->data_size;
                        fsg->phase_error = 1;
                }
        }
        fsg->residue = fsg->usb_amount_left = fsg->data_size;

        /* Conflicting data directions is a phase error */
        if (fsg->data_dir != data_dir && fsg->data_size_from_cmnd > 0) {
                fsg->phase_error = 1;
                return -EINVAL;
        }

        /* Verify the length of the command itself */
        if (cmnd_size != fsg->cmnd_size) {

                /* Special case workaround: There are plenty of buggy SCSI
                 * implementations. Many have issues with cbw->Length
                 * field passing a wrong command size. For those cases we
                 * always try to work around the problem by using the length
                 * sent by the host side provided it is at least as large
                 * as the correct command length.
                 * Examples of such cases would be MS-Windows, which issues
                 * REQUEST SENSE with cbw->Length == 12 where it should
                 * be 6, and xbox360 issuing INQUIRY, TEST UNIT READY and
                 * REQUEST SENSE with cbw->Length == 10 where it should
                 * be 6 as well.
                 */
                if (cmnd_size <= fsg->cmnd_size) {
                        DBG(fsg, "%s is buggy! Expected length %d "
                                        "but we got %d\n", name,
                                        cmnd_size, fsg->cmnd_size);
                        cmnd_size = fsg->cmnd_size;
                } else {
                        fsg->phase_error = 1;
                        return -EINVAL;
                }
        }

        /* Check that the LUN values are consistent */
        if (fsg->lun != lun)
                DBG(fsg, "using LUN %d from CBW, not LUN %d from CDB\n",
                    fsg->lun, lun);

        /* Check the LUN */
        if (fsg->lun >= 0 && fsg->lun < fsg->nluns) {
                fsg->curlun = curlun = &fsg->luns[fsg->lun];
                if (fsg->cmnd[0] != SC_REQUEST_SENSE) {
                        curlun->sense_data = SS_NO_SENSE;
                        curlun->sense_data_info = 0;
                        curlun->info_valid = 0;
                }
        } else {
                fsg->curlun = curlun = NULL;
                fsg->bad_lun_okay = 0;

                /* INQUIRY and REQUEST SENSE commands are explicitly allowed
                 * to use unsupported LUNs; all others may not. */
                if (fsg->cmnd[0] != SC_INQUIRY &&
                                fsg->cmnd[0] != SC_REQUEST_SENSE) {
                        DBG(fsg, "unsupported LUN %d\n", fsg->lun);
                        return -EINVAL;
                }
        }

        /* If a unit attention condition exists, only INQUIRY and
         * REQUEST SENSE commands are allowed; anything else must fail. */
        if (curlun && curlun->unit_attention_data != SS_NO_SENSE &&
                        fsg->cmnd[0] != SC_INQUIRY &&
                        fsg->cmnd[0] != SC_REQUEST_SENSE) {
                curlun->sense_data = curlun->unit_attention_data;
                curlun->unit_attention_data = SS_NO_SENSE;
                return -EINVAL;
        }

        /* Check that only command bytes listed in the mask are non-zero */
        fsg->cmnd[1] &= 0x1f;                   // Mask away the LUN
        for (i = 1; i < cmnd_size; ++i) {
                if (fsg->cmnd[i] && !(mask & (1 << i))) {
                        if (curlun)
                                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
        }

        /* If the medium isn't mounted and the command needs to access
         * it, return an error. */
        if (curlun && !fsg_lun_is_open(curlun) && needs_medium) {
                curlun->sense_data = SS_MEDIUM_NOT_PRESENT;
                return -EINVAL;
        }

        return 0;
}


static int do_scsi_command(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh;
        int                     rc;
        int                     reply = -EINVAL;
        int                     i;
        static char             unknown[16];

        dump_cdb(fsg);

        /* Wait for the next buffer to become available for data or status */
        bh = fsg->next_buffhd_to_drain = fsg->next_buffhd_to_fill;
        while (bh->state != BUF_STATE_EMPTY) {
                rc = sleep_thread(fsg);
                if (rc)
                        return rc;
        }
        fsg->phase_error = 0;
        fsg->short_packet_received = 0;

        down_read(&fsg->filesem);       // We're using the backing file
        switch (fsg->cmnd[0]) {

        case SC_INQUIRY:
                fsg->data_size_from_cmnd = fsg->cmnd[4];
                if ((reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                                (1<<4), 0,
                                "INQUIRY")) == 0)
                        reply = do_inquiry(fsg, bh);
                break;

        case SC_MODE_SELECT_6:
                fsg->data_size_from_cmnd = fsg->cmnd[4];
                if ((reply = check_command(fsg, 6, DATA_DIR_FROM_HOST,
                                (1<<1) | (1<<4), 0,
                                "MODE SELECT(6)")) == 0)
                        reply = do_mode_select(fsg, bh);
                break;

        case SC_MODE_SELECT_10:
                fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
                if ((reply = check_command(fsg, 10, DATA_DIR_FROM_HOST,
                                (1<<1) | (3<<7), 0,
                                "MODE SELECT(10)")) == 0)
                        reply = do_mode_select(fsg, bh);
                break;

        case SC_MODE_SENSE_6:
                fsg->data_size_from_cmnd = fsg->cmnd[4];
                if ((reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                                (1<<1) | (1<<2) | (1<<4), 0,
                                "MODE SENSE(6)")) == 0)
                        reply = do_mode_sense(fsg, bh);
                break;

        case SC_MODE_SENSE_10:
                fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
                if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                (1<<1) | (1<<2) | (3<<7), 0,
                                "MODE SENSE(10)")) == 0)
                        reply = do_mode_sense(fsg, bh);
                break;

        case SC_PREVENT_ALLOW_MEDIUM_REMOVAL:
                fsg->data_size_from_cmnd = 0;
                if ((reply = check_command(fsg, 6, DATA_DIR_NONE,
                                (1<<4), 0,
                                "PREVENT-ALLOW MEDIUM REMOVAL")) == 0)
                        reply = do_prevent_allow(fsg);
                break;

        case SC_READ_6:
                i = fsg->cmnd[4];
                fsg->data_size_from_cmnd = (i == 0 ? 256 : i) << 9;
                if ((reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                                (7<<1) | (1<<4), 1,
                                "READ(6)")) == 0)
                        reply = do_read(fsg);
                break;

        case SC_READ_10:
                fsg->data_size_from_cmnd =
                                get_unaligned_be16(&fsg->cmnd[7]) << 9;
                if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                (1<<1) | (0xf<<2) | (3<<7), 1,
                                "READ(10)")) == 0)
                        reply = do_read(fsg);
                break;

        case SC_READ_12:
                fsg->data_size_from_cmnd =
                                get_unaligned_be32(&fsg->cmnd[6]) << 9;
                if ((reply = check_command(fsg, 12, DATA_DIR_TO_HOST,
                                (1<<1) | (0xf<<2) | (0xf<<6), 1,
                                "READ(12)")) == 0)
                        reply = do_read(fsg);
                break;

        case SC_READ_CAPACITY:
                fsg->data_size_from_cmnd = 8;
                if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                (0xf<<2) | (1<<8), 1,
                                "READ CAPACITY")) == 0)
                        reply = do_read_capacity(fsg, bh);
                break;

        case SC_READ_HEADER:
                if (!mod_data.cdrom)
                        goto unknown_cmnd;
                fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
                if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                (3<<7) | (0x1f<<1), 1,
                                "READ HEADER")) == 0)
                        reply = do_read_header(fsg, bh);
                break;

        case SC_READ_TOC:
                if (!mod_data.cdrom)
                        goto unknown_cmnd;
                fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
                if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                (7<<6) | (1<<1), 1,
                                "READ TOC")) == 0)
                        reply = do_read_toc(fsg, bh);
                break;

        case SC_READ_FORMAT_CAPACITIES:
                fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
                if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                (3<<7), 1,
                                "READ FORMAT CAPACITIES")) == 0)
                        reply = do_read_format_capacities(fsg, bh);
                break;

        case SC_REQUEST_SENSE:
                fsg->data_size_from_cmnd = fsg->cmnd[4];
                if ((reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                                (1<<4), 0,
                                "REQUEST SENSE")) == 0)
                        reply = do_request_sense(fsg, bh);
                break;

        case SC_START_STOP_UNIT:
                fsg->data_size_from_cmnd = 0;
                if ((reply = check_command(fsg, 6, DATA_DIR_NONE,
                                (1<<1) | (1<<4), 0,
                                "START-STOP UNIT")) == 0)
                        reply = do_start_stop(fsg);
                break;

        case SC_SYNCHRONIZE_CACHE:
                fsg->data_size_from_cmnd = 0;
                if ((reply = check_command(fsg, 10, DATA_DIR_NONE,
                                (0xf<<2) | (3<<7), 1,
                                "SYNCHRONIZE CACHE")) == 0)
                        reply = do_synchronize_cache(fsg);
                break;

        case SC_TEST_UNIT_READY:
                fsg->data_size_from_cmnd = 0;
                reply = check_command(fsg, 6, DATA_DIR_NONE,
                                0, 1,
                                "TEST UNIT READY");
                break;

        /* Although optional, this command is used by MS-Windows.  We
         * support a minimal version: BytChk must be 0. */
        case SC_VERIFY:
                fsg->data_size_from_cmnd = 0;
                if ((reply = check_command(fsg, 10, DATA_DIR_NONE,
                                (1<<1) | (0xf<<2) | (3<<7), 1,
                                "VERIFY")) == 0)
                        reply = do_verify(fsg);
                break;

        case SC_WRITE_6:
                i = fsg->cmnd[4];
                fsg->data_size_from_cmnd = (i == 0 ? 256 : i) << 9;
                if ((reply = check_command(fsg, 6, DATA_DIR_FROM_HOST,
                                (7<<1) | (1<<4), 1,
                                "WRITE(6)")) == 0)
                        reply = do_write(fsg);
                break;

        case SC_WRITE_10:
                fsg->data_size_from_cmnd =
                                get_unaligned_be16(&fsg->cmnd[7]) << 9;
                if ((reply = check_command(fsg, 10, DATA_DIR_FROM_HOST,
                                (1<<1) | (0xf<<2) | (3<<7), 1,
                                "WRITE(10)")) == 0)
                        reply = do_write(fsg);
                break;

        case SC_WRITE_12:
                fsg->data_size_from_cmnd =
                                get_unaligned_be32(&fsg->cmnd[6]) << 9;
                if ((reply = check_command(fsg, 12, DATA_DIR_FROM_HOST,
                                (1<<1) | (0xf<<2) | (0xf<<6), 1,
                                "WRITE(12)")) == 0)
                        reply = do_write(fsg);
                break;

        /* Some mandatory commands that we recognize but don't implement.
         * They don't mean much in this setting.  It's left as an exercise
         * for anyone interested to implement RESERVE and RELEASE in terms
         * of Posix locks. */
        case SC_FORMAT_UNIT:
        case SC_RELEASE:
        case SC_RESERVE:
        case SC_SEND_DIAGNOSTIC:
                // Fall through

        default:
 unknown_cmnd:
                fsg->data_size_from_cmnd = 0;
                sprintf(unknown, "Unknown x%02x", fsg->cmnd[0]);
                if ((reply = check_command(fsg, fsg->cmnd_size,
                                DATA_DIR_UNKNOWN, 0xff, 0, unknown)) == 0) {
                        fsg->curlun->sense_data = SS_INVALID_COMMAND;
                        reply = -EINVAL;
                }
                break;
        }
        up_read(&fsg->filesem);

        if (reply == -EINTR || signal_pending(current))
                return -EINTR;

        /* Set up the single reply buffer for finish_reply() */
        if (reply == -EINVAL)
                reply = 0;              // Error reply length
        if (reply >= 0 && fsg->data_dir == DATA_DIR_TO_HOST) {
                reply = min((u32) reply, fsg->data_size_from_cmnd);
                bh->inreq->length = reply;
                bh->state = BUF_STATE_FULL;
                fsg->residue -= reply;
        }                               // Otherwise it's already set

        return 0;
}


/*-------------------------------------------------------------------------*/

static int received_cbw(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct usb_request              *req = bh->outreq;
        struct fsg_bulk_cb_wrap *cbw = req->buf;

        /* Was this a real packet?  Should it be ignored? */
        if (req->status || test_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags))
                return -EINVAL;

        /* Is the CBW valid? */
        if (req->actual != USB_BULK_CB_WRAP_LEN ||
                        cbw->Signature != cpu_to_le32(
                                USB_BULK_CB_SIG)) {
                DBG(fsg, "invalid CBW: len %u sig 0x%x\n",
                                req->actual,
                                le32_to_cpu(cbw->Signature));

                /* The Bulk-only spec says we MUST stall the IN endpoint
                 * (6.6.1), so it's unavoidable.  It also says we must
                 * retain this state until the next reset, but there's
                 * no way to tell the controller driver it should ignore
                 * Clear-Feature(HALT) requests.
                 *
                 * We aren't required to halt the OUT endpoint; instead
                 * we can simply accept and discard any data received
                 * until the next reset. */
                wedge_bulk_in_endpoint(fsg);
                set_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);
                return -EINVAL;
        }

        /* Is the CBW meaningful? */
        if (cbw->Lun >= FSG_MAX_LUNS || cbw->Flags & ~USB_BULK_IN_FLAG ||
                        cbw->Length <= 0 || cbw->Length > MAX_COMMAND_SIZE) {
                DBG(fsg, "non-meaningful CBW: lun = %u, flags = 0x%x, "
                                "cmdlen %u\n",
                                cbw->Lun, cbw->Flags, cbw->Length);

                /* We can do anything we want here, so let's stall the
                 * bulk pipes if we are allowed to. */
                if (mod_data.can_stall) {
                        fsg_set_halt(fsg, fsg->bulk_out);
                        halt_bulk_in_endpoint(fsg);
                }
                return -EINVAL;
        }

        /* Save the command for later */
        fsg->cmnd_size = cbw->Length;
        memcpy(fsg->cmnd, cbw->CDB, fsg->cmnd_size);
        if (cbw->Flags & USB_BULK_IN_FLAG)
                fsg->data_dir = DATA_DIR_TO_HOST;
        else
                fsg->data_dir = DATA_DIR_FROM_HOST;
        fsg->data_size = le32_to_cpu(cbw->DataTransferLength);
        if (fsg->data_size == 0)
                fsg->data_dir = DATA_DIR_NONE;
        fsg->lun = cbw->Lun;
        fsg->tag = cbw->Tag;
        return 0;
}


static int get_next_command(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh;
        int                     rc = 0;

        /* Wait for the next buffer to become available */
        bh = fsg->next_buffhd_to_fill;
        while (bh->state != BUF_STATE_EMPTY) {
                rc = sleep_thread(fsg);
                if (rc)
                        return rc;
        }

        /* Queue a request to read a Bulk-only CBW */
        set_bulk_out_req_length(fsg, bh, USB_BULK_CB_WRAP_LEN);
        bh->outreq->short_not_ok = 1;
        start_transfer(fsg, fsg->bulk_out, bh->outreq,
                       &bh->outreq_busy, &bh->state);

        /* We will drain the buffer in software, which means we
         * can reuse it for the next filling.  No need to advance
         * next_buffhd_to_fill. */

        /* Wait for the CBW to arrive */
        while (bh->state != BUF_STATE_FULL) {
                rc = sleep_thread(fsg);
                if (rc)
                        return rc;
        }
        smp_rmb();
        rc = received_cbw(fsg, bh);
        bh->state = BUF_STATE_EMPTY;

        return rc;
}


/*-------------------------------------------------------------------------*/

static int enable_endpoint(struct fsg_dev *fsg, struct usb_ep *ep,
                const struct usb_endpoint_descriptor *d)
{
        int     rc;

        ep->driver_data = fsg;
        rc = usb_ep_enable(ep, d);
        if (rc)
                ERROR(fsg, "can't enable %s, result %d\n", ep->name, rc);
        return rc;
}

static int alloc_request(struct fsg_dev *fsg, struct usb_ep *ep,
                struct usb_request **preq)
{
        *preq = usb_ep_alloc_request(ep, GFP_ATOMIC);
        if (*preq)
                return 0;
        ERROR(fsg, "can't allocate request for %s\n", ep->name);
        return -ENOMEM;
}

/*
 * Reset interface setting and re-init endpoint state (toggle etc).
 * Call with altsetting < 0 to disable the interface.  The only other
 * available altsetting is 0, which enables the interface.
 */
static int do_set_interface(struct fsg_dev *fsg, int altsetting)
{
        int     rc = 0;
        int     i;
        const struct usb_endpoint_descriptor    *d;

        if (fsg->running)
                DBG(fsg, "reset interface\n");

reset:
        /* Deallocate the requests */
        for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
                struct fsg_buffhd *bh = &fsg->buffhds[i];

                if (bh->inreq) {
                        usb_ep_free_request(fsg->bulk_in, bh->inreq);
                        bh->inreq = NULL;
                }
                if (bh->outreq) {
                        usb_ep_free_request(fsg->bulk_out, bh->outreq);
                        bh->outreq = NULL;
                }
        }

        /* Disable the endpoints */
        if (fsg->bulk_in_enabled) {
                usb_ep_disable(fsg->bulk_in);
                fsg->bulk_in_enabled = 0;
        }
        if (fsg->bulk_out_enabled) {
                usb_ep_disable(fsg->bulk_out);
                fsg->bulk_out_enabled = 0;
        }

        fsg->running = 0;
        if (altsetting < 0 || rc != 0)
                return rc;

        DBG(fsg, "set interface %d\n", altsetting);

        /* Enable the endpoints */
        d = fsg_ep_desc(fsg->gadget,
                        &fsg_fs_bulk_in_desc, &fsg_hs_bulk_in_desc);
        if ((rc = enable_endpoint(fsg, fsg->bulk_in, d)) != 0)
                goto reset;
        fsg->bulk_in_enabled = 1;

        d = fsg_ep_desc(fsg->gadget,
                        &fsg_fs_bulk_out_desc, &fsg_hs_bulk_out_desc);
        if ((rc = enable_endpoint(fsg, fsg->bulk_out, d)) != 0)
                goto reset;
        fsg->bulk_out_enabled = 1;
        fsg->bulk_out_maxpacket = le16_to_cpu(d->wMaxPacketSize);
        clear_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);

        /* Allocate the requests */
        for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
                struct fsg_buffhd       *bh = &fsg->buffhds[i];

                if ((rc = alloc_request(fsg, fsg->bulk_in, &bh->inreq)) != 0)
                        goto reset;
                if ((rc = alloc_request(fsg, fsg->bulk_out, &bh->outreq)) != 0)
                        goto reset;
                bh->inreq->buf = bh->outreq->buf = bh->buf;
                bh->inreq->context = bh->outreq->context = bh;
                bh->inreq->complete = bulk_in_complete;
                bh->outreq->complete = bulk_out_complete;
        }

        fsg->running = 1;
        for (i = 0; i < fsg->nluns; ++i)
                fsg->luns[i].unit_attention_data = SS_RESET_OCCURRED;
        return rc;
}


/*
 * Change our operational configuration.  This code must agree with the code
 * that returns config descriptors, and with interface altsetting code.
 *
 * It's also responsible for power management interactions.  Some
 * configurations might not work with our current power sources.
 * For now we just assume the gadget is always self-powered.
 */
static int do_set_config(struct fsg_dev *fsg, u8 new_config)
{
        int     rc = 0;

        /* Disable the single interface */
        if (fsg->config != 0) {
                DBG(fsg, "reset config\n");
                fsg->config = 0;
                rc = do_set_interface(fsg, -1);
        }

        /* Enable the interface */
        if (new_config != 0) {
                fsg->config = new_config;
                if ((rc = do_set_interface(fsg, 0)) != 0)
                        fsg->config = 0;        // Reset on errors
                else {
                        char *speed;

                        switch (fsg->gadget->speed) {
                        case USB_SPEED_LOW:     speed = "low";  break;
                        case USB_SPEED_FULL:    speed = "full"; break;
                        case USB_SPEED_HIGH:    speed = "high"; break;
                        default:                speed = "?";    break;
                        }
                        INFO(fsg, "%s speed config #%d\n", speed, fsg->config);
                }
        }
        return rc;
}


/*-------------------------------------------------------------------------*/

static void handle_exception(struct fsg_dev *fsg)
{
        siginfo_t               info;
        int                     sig;
        int                     i;
        int                     num_active;
        struct fsg_buffhd       *bh;
        enum fsg_state          old_state;
        u8                      new_config;
        struct fsg_lun          *curlun;
        unsigned int            exception_req_tag;
        int                     rc;

        /* Clear the existing signals.  Anything but SIGUSR1 is converted
         * into a high-priority EXIT exception. */
        for (;;) {
                sig = dequeue_signal_lock(current, &current->blocked, &info);
                if (!sig)
                        break;
                if (sig != SIGUSR1) {
                        if (fsg->state < FSG_STATE_EXIT)
                                DBG(fsg, "Main thread exiting on signal\n");
                        raise_exception(fsg, FSG_STATE_EXIT);
                }
        }

        /* Cancel all the pending transfers */
        for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
                bh = &fsg->buffhds[i];
                if (bh->inreq_busy)
                        usb_ep_dequeue(fsg->bulk_in, bh->inreq);
                if (bh->outreq_busy)
                        usb_ep_dequeue(fsg->bulk_out, bh->outreq);
        }

        /* Wait until everything is idle */
        for (;;) {
                num_active = 0;
                for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
                        bh = &fsg->buffhds[i];
                        num_active += bh->inreq_busy + bh->outreq_busy;
                }
                if (num_active == 0)
                        break;
                if (sleep_thread(fsg))
                        return;
        }

        /* Clear out the controller's fifos */
        if (fsg->bulk_in_enabled)
                usb_ep_fifo_flush(fsg->bulk_in);
        if (fsg->bulk_out_enabled)
                usb_ep_fifo_flush(fsg->bulk_out);

        /* Reset the I/O buffer states and pointers, the SCSI
         * state, and the exception.  Then invoke the handler. */
        spin_lock_irq(&fsg->lock);

        for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
                bh = &fsg->buffhds[i];
                bh->state = BUF_STATE_EMPTY;
        }
        fsg->next_buffhd_to_fill = fsg->next_buffhd_to_drain =
                        &fsg->buffhds[0];

        exception_req_tag = fsg->exception_req_tag;
        new_config = fsg->new_config;
        old_state = fsg->state;

        if (old_state == FSG_STATE_ABORT_BULK_OUT)
                fsg->state = FSG_STATE_STATUS_PHASE;
        else {
                for (i = 0; i < fsg->nluns; ++i) {
                        curlun = &fsg->luns[i];
                        curlun->prevent_medium_removal = 0;
                        curlun->sense_data = curlun->unit_attention_data =
                                        SS_NO_SENSE;
                        curlun->sense_data_info = 0;
                        curlun->info_valid = 0;
                }
                fsg->state = FSG_STATE_IDLE;
        }
        spin_unlock_irq(&fsg->lock);

        /* Carry out any extra actions required for the exception */
        switch (old_state) {
        default:
                break;

        case FSG_STATE_ABORT_BULK_OUT:
                send_status(fsg);
                spin_lock_irq(&fsg->lock);
                if (fsg->state == FSG_STATE_STATUS_PHASE)
                        fsg->state = FSG_STATE_IDLE;
                spin_unlock_irq(&fsg->lock);
                break;

        case FSG_STATE_RESET:
                /* In case we were forced against our will to halt a
                 * bulk endpoint, clear the halt now.  (The SuperH UDC
                 * requires this.) */
                if (test_and_clear_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags))
                        usb_ep_clear_halt(fsg->bulk_in);

                if (fsg->ep0_req_tag == exception_req_tag)
                        ep0_queue(fsg); // Complete the status stage

                /* Technically this should go here, but it would only be
                 * a waste of time.  Ditto for the INTERFACE_CHANGE and
                 * CONFIG_CHANGE cases. */
                // for (i = 0; i < fsg->nluns; ++i)
                //      fsg->luns[i].unit_attention_data = SS_RESET_OCCURRED;
                break;

        case FSG_STATE_INTERFACE_CHANGE:
                rc = do_set_interface(fsg, 0);
                if (fsg->ep0_req_tag != exception_req_tag)
                        break;
                if (rc != 0)                    // STALL on errors
                        fsg_set_halt(fsg, fsg->ep0);
                else                            // Complete the status stage
                        ep0_queue(fsg);
                break;

        case FSG_STATE_CONFIG_CHANGE:
                rc = do_set_config(fsg, new_config);
                if (fsg->ep0_req_tag != exception_req_tag)
                        break;
                if (rc != 0)                    // STALL on errors
                        fsg_set_halt(fsg, fsg->ep0);
                else                            // Complete the status stage
                        ep0_queue(fsg);
                break;

        case FSG_STATE_DISCONNECT:
                for (i = 0; i < fsg->nluns; ++i)
                        fsg_lun_fsync_sub(fsg->luns + i);
                do_set_config(fsg, 0);          // Unconfigured state
                break;

        case FSG_STATE_EXIT:
        case FSG_STATE_TERMINATED:
                do_set_config(fsg, 0);                  // Free resources
                spin_lock_irq(&fsg->lock);
                fsg->state = FSG_STATE_TERMINATED;      // Stop the thread
                spin_unlock_irq(&fsg->lock);
                break;
        }
}


/*-------------------------------------------------------------------------*/

static int fsg_main_thread(void *fsg_)
{
        struct fsg_dev          *fsg = fsg_;

        /* Allow the thread to be killed by a signal, but set the signal mask
         * to block everything but INT, TERM, KILL, and USR1. */
        allow_signal(SIGINT);
        allow_signal(SIGTERM);
        allow_signal(SIGKILL);
        allow_signal(SIGUSR1);

        /* Allow the thread to be frozen */
        set_freezable();

        /* Arrange for userspace references to be interpreted as kernel
         * pointers.  That way we can pass a kernel pointer to a routine
         * that expects a __user pointer and it will work okay. */
        set_fs(get_ds());

        /* The main loop */
        while (fsg->state != FSG_STATE_TERMINATED) {
                if (exception_in_progress(fsg) || signal_pending(current)) {
                        handle_exception(fsg);
                        continue;
                }

                if (!fsg->running) {
                        sleep_thread(fsg);
                        continue;
                }

                if (get_next_command(fsg))
                        continue;

                spin_lock_irq(&fsg->lock);
                if (!exception_in_progress(fsg))
                        fsg->state = FSG_STATE_DATA_PHASE;
                spin_unlock_irq(&fsg->lock);

                if (do_scsi_command(fsg) || finish_reply(fsg))
                        continue;

                spin_lock_irq(&fsg->lock);
                if (!exception_in_progress(fsg))
                        fsg->state = FSG_STATE_STATUS_PHASE;
                spin_unlock_irq(&fsg->lock);

                if (send_status(fsg))
                        continue;

                spin_lock_irq(&fsg->lock);
                if (!exception_in_progress(fsg))
                        fsg->state = FSG_STATE_IDLE;
                spin_unlock_irq(&fsg->lock);
                }

        spin_lock_irq(&fsg->lock);
        fsg->thread_task = NULL;
        spin_unlock_irq(&fsg->lock);

        /* If we are exiting because of a signal, unregister the
         * gadget driver. */
        if (test_and_clear_bit(REGISTERED, &fsg->atomic_bitflags))
                usb_gadget_unregister_driver(&fsg_driver);

        /* Let the unbind and cleanup routines know the thread has exited */
        complete_and_exit(&fsg->thread_notifier, 0);
}


/*-------------------------------------------------------------------------*/


/* The write permissions and store_xxx pointers are set in fsg_bind() */
static DEVICE_ATTR(ro, 0444, fsg_show_ro, NULL);
static DEVICE_ATTR(file, 0444, fsg_show_file, NULL);


/*-------------------------------------------------------------------------*/

static void fsg_release(struct kref *ref)
{
        struct fsg_dev  *fsg = container_of(ref, struct fsg_dev, ref);

        kfree(fsg->luns);
        kfree(fsg);
}

static void lun_release(struct device *dev)
{
        struct rw_semaphore     *filesem = dev_get_drvdata(dev);
        struct fsg_dev          *fsg =
                container_of(filesem, struct fsg_dev, filesem);

        kref_put(&fsg->ref, fsg_release);
}

static void /* __init_or_exit */ fsg_unbind(struct usb_gadget *gadget)
{
        struct fsg_dev          *fsg = get_gadget_data(gadget);
        int                     i;
        struct fsg_lun          *curlun;
        struct usb_request      *req = fsg->ep0req;

        DBG(fsg, "unbind\n");
        clear_bit(REGISTERED, &fsg->atomic_bitflags);

        /* Unregister the sysfs attribute files and the LUNs */
        for (i = 0; i < fsg->nluns; ++i) {
                curlun = &fsg->luns[i];
                if (curlun->registered) {
                        device_remove_file(&curlun->dev, &dev_attr_ro);
                        device_remove_file(&curlun->dev, &dev_attr_file);
                        fsg_lun_close(curlun);
                        device_unregister(&curlun->dev);
                        curlun->registered = 0;
                }
        }

        /* If the thread isn't already dead, tell it to exit now */
        if (fsg->state != FSG_STATE_TERMINATED) {
                raise_exception(fsg, FSG_STATE_EXIT);
                wait_for_completion(&fsg->thread_notifier);

                /* The cleanup routine waits for this completion also */
                complete(&fsg->thread_notifier);
        }

        /* Free the data buffers */
        for (i = 0; i < FSG_NUM_BUFFERS; ++i)
                kfree(fsg->buffhds[i].buf);

        /* Free the request and buffer for endpoint 0 */
        if (req) {
                kfree(req->buf);
                usb_ep_free_request(fsg->ep0, req);
        }

        set_gadget_data(gadget, NULL);
}


static int __init check_parameters(struct fsg_dev *fsg)
{
        int     gcnum;

        /* Some peripheral controllers are known not to be able to
         * halt bulk endpoints correctly.  If one of them is present,
         * disable stalls.
         */
        if (gadget_is_sh(fsg->gadget) || gadget_is_at91(fsg->gadget))
                mod_data.can_stall = 0;

        if (mod_data.release == 0xffff) {       // Parameter wasn't set
                /* The sa1100 controller is not supported */
                if (gadget_is_sa1100(fsg->gadget))
                        gcnum = -1;
                else
                        gcnum = usb_gadget_controller_number(fsg->gadget);
                if (gcnum >= 0)
                        mod_data.release = 0x0300 + gcnum;
                else {
                        WARNING(fsg, "controller '%s' not recognized\n",
                                fsg->gadget->name);
                        mod_data.release = 0x0399;
                }
        }

        return 0;
}


static int __init fsg_bind(struct usb_gadget *gadget)
{
        struct fsg_dev          *fsg = the_fsg;
        int                     rc;
        int                     i;
        struct fsg_lun          *curlun;
        struct usb_ep           *ep;
        struct usb_request      *req;
        char                    *pathbuf, *p;

        fsg->gadget = gadget;
        set_gadget_data(gadget, fsg);
        fsg->ep0 = gadget->ep0;
        fsg->ep0->driver_data = fsg;

        if ((rc = check_parameters(fsg)) != 0)
                goto out;

        if (mod_data.removable) {       // Enable the store_xxx attributes
                dev_attr_file.attr.mode = 0644;
                dev_attr_file.store = fsg_store_file;
                if (!mod_data.cdrom) {
                        dev_attr_ro.attr.mode = 0644;
                        dev_attr_ro.store = fsg_store_ro;
                }
        }

        /* Find out how many LUNs there should be */
        i = mod_data.nluns;
        if (i == 0)
                i = max(mod_data.num_filenames, 1u);
        if (i > FSG_MAX_LUNS) {
                ERROR(fsg, "invalid number of LUNs: %d\n", i);
                rc = -EINVAL;
                goto out;
        }

        /* Create the LUNs, open their backing files, and register the
         * LUN devices in sysfs. */
        fsg->luns = kzalloc(i * sizeof(struct fsg_lun), GFP_KERNEL);
        if (!fsg->luns) {
                rc = -ENOMEM;
                goto out;
        }
        fsg->nluns = i;

        for (i = 0; i < fsg->nluns; ++i) {
                curlun = &fsg->luns[i];
                curlun->cdrom = !!mod_data.cdrom;
                curlun->ro = mod_data.cdrom || mod_data.ro[i];
                curlun->initially_ro = curlun->ro;
                curlun->removable = mod_data.removable;
                curlun->dev.release = lun_release;
                curlun->dev.parent = &gadget->dev;
                curlun->dev.driver = &fsg_driver.driver;
                dev_set_drvdata(&curlun->dev, &fsg->filesem);
                dev_set_name(&curlun->dev,"%s-lun%d",
                             dev_name(&gadget->dev), i);

                if ((rc = device_register(&curlun->dev)) != 0) {
                        INFO(fsg, "failed to register LUN%d: %d\n", i, rc);
                        goto out;
                }
                if ((rc = device_create_file(&curlun->dev,
                                        &dev_attr_ro)) != 0 ||
                                (rc = device_create_file(&curlun->dev,
                                        &dev_attr_file)) != 0) {
                        device_unregister(&curlun->dev);
                        goto out;
                }
                curlun->registered = 1;
                kref_get(&fsg->ref);

                if (mod_data.file[i] && *mod_data.file[i]) {
                        if ((rc = fsg_lun_open(curlun,
                                        mod_data.file[i])) != 0)
                                goto out;
                } else if (!mod_data.removable) {
                        ERROR(fsg, "no file given for LUN%d\n", i);
                        rc = -EINVAL;
                        goto out;
                }
        }

        /* Find all the endpoints we will use */
        usb_ep_autoconfig_reset(gadget);
        ep = usb_ep_autoconfig(gadget, &fsg_fs_bulk_in_desc);
        if (!ep)
                goto autoconf_fail;
        ep->driver_data = fsg;          // claim the endpoint
        fsg->bulk_in = ep;

        ep = usb_ep_autoconfig(gadget, &fsg_fs_bulk_out_desc);
        if (!ep)
                goto autoconf_fail;
        ep->driver_data = fsg;          // claim the endpoint
        fsg->bulk_out = ep;

        /* Fix up the descriptors */
        device_desc.bMaxPacketSize0 = fsg->ep0->maxpacket;
        device_desc.bcdDevice = cpu_to_le16(mod_data.release);

        if (gadget_is_dualspeed(gadget)) {
                /* Assume ep0 uses the same maxpacket value for both speeds */
                dev_qualifier.bMaxPacketSize0 = fsg->ep0->maxpacket;

                /* Assume endpoint addresses are the same for both speeds */
                fsg_hs_bulk_in_desc.bEndpointAddress =
                        fsg_fs_bulk_in_desc.bEndpointAddress;
                fsg_hs_bulk_out_desc.bEndpointAddress =
                        fsg_fs_bulk_out_desc.bEndpointAddress;
        }

        if (gadget_is_otg(gadget))
                fsg_otg_desc.bmAttributes |= USB_OTG_HNP;

        rc = -ENOMEM;

        /* Allocate the request and buffer for endpoint 0 */
        fsg->ep0req = req = usb_ep_alloc_request(fsg->ep0, GFP_KERNEL);
        if (!req)
                goto out;
        req->buf = kmalloc(EP0_BUFSIZE, GFP_KERNEL);
        if (!req->buf)
                goto out;
        req->complete = ep0_complete;

        /* Allocate the data buffers */
        for (i = 0; i < FSG_NUM_BUFFERS; ++i) {
                struct fsg_buffhd       *bh = &fsg->buffhds[i];

                /* Allocate for the bulk-in endpoint.  We assume that
                 * the buffer will also work with the bulk-out (and
                 * interrupt-in) endpoint. */
                bh->buf = kmalloc(FSG_BUFLEN, GFP_KERNEL);
                if (!bh->buf)
                        goto out;
                bh->next = bh + 1;
        }
        fsg->buffhds[FSG_NUM_BUFFERS - 1].next = &fsg->buffhds[0];

        /* This should reflect the actual gadget power source */
        usb_gadget_set_selfpowered(gadget);

        snprintf(fsg_string_manufacturer, sizeof fsg_string_manufacturer,
                        "%s %s with %s",
                        init_utsname()->sysname, init_utsname()->release,
                        gadget->name);

        /* On a real device, serial[] would be loaded from permanent
         * storage.  We just encode it from the driver version string. */
        for (i = 0; i < sizeof fsg_string_serial - 2; i += 2) {
                unsigned char           c = DRIVER_VERSION[i / 2];

                if (!c)
                        break;
                sprintf(&fsg_string_serial[i], "%02X", c);
        }

        fsg->thread_task = kthread_create(fsg_main_thread, fsg,
                        "file-storage-gadget");
        if (IS_ERR(fsg->thread_task)) {