USB: gadget: f_audio_source: New gadget driver for audio output
Mike Lockwood [Fri, 11 May 2012 16:01:08 +0000 (09:01 -0700)]
This driver presents a standard USB audio class interface to the host
and an ALSA PCM device to userspace

Bug 1026047

Signed-off-by: Mike Lockwood <lockwood@google.com>
(cherry picked from commit a23ff394752015a233dd3b27b05c9d913cbf5536)

Signed-off-by: Rakesh Bodla <rbodla@nvidia.com>
Change-Id: I4054e09888f17d9cdfcfd4a3d430ca5cfb3fd9fa
Reviewed-on: http://git-master/r/123343
Reviewed-by: Venkat Moganty <vmoganty@nvidia.com>

drivers/usb/gadget/android.c
drivers/usb/gadget/f_audio_source.c [new file with mode: 0644]

index e23557e..7b3185f 100644 (file)
@@ -45,6 +45,7 @@
 #include "epautoconf.c"
 #include "composite.c"
 
+#include "f_audio_source.c"
 #include "f_mass_storage.c"
 #include "u_serial.c"
 #include "f_acm.c"
@@ -649,6 +650,67 @@ static struct android_usb_function accessory_function = {
        .ctrlrequest    = accessory_function_ctrlrequest,
 };
 
+static int audio_source_function_init(struct android_usb_function *f,
+                       struct usb_composite_dev *cdev)
+{
+       struct audio_source_config *config;
+
+       config = kzalloc(sizeof(struct audio_source_config), GFP_KERNEL);
+       if (!config)
+               return -ENOMEM;
+       config->card = -1;
+       config->device = -1;
+       f->config = config;
+       return 0;
+}
+
+static void audio_source_function_cleanup(struct android_usb_function *f)
+{
+       kfree(f->config);
+}
+
+static int audio_source_function_bind_config(struct android_usb_function *f,
+                                               struct usb_configuration *c)
+{
+       struct audio_source_config *config = f->config;
+
+       return audio_source_bind_config(c, config);
+}
+
+static void audio_source_function_unbind_config(struct android_usb_function *f,
+                                               struct usb_configuration *c)
+{
+       struct audio_source_config *config = f->config;
+
+       config->card = -1;
+       config->device = -1;
+}
+
+static ssize_t audio_source_pcm_show(struct device *dev,
+               struct device_attribute *attr, char *buf)
+{
+       struct android_usb_function *f = dev_get_drvdata(dev);
+       struct audio_source_config *config = f->config;
+
+       /* print PCM card and device numbers */
+       return sprintf(buf, "%d %d\n", config->card, config->device);
+}
+
+static DEVICE_ATTR(pcm, S_IRUGO | S_IWUSR, audio_source_pcm_show, NULL);
+
+static struct device_attribute *audio_source_function_attributes[] = {
+       &dev_attr_pcm,
+       NULL
+};
+
+static struct android_usb_function audio_source_function = {
+       .name           = "audio_source",
+       .init           = audio_source_function_init,
+       .cleanup        = audio_source_function_cleanup,
+       .bind_config    = audio_source_function_bind_config,
+       .unbind_config  = audio_source_function_unbind_config,
+       .attributes     = audio_source_function_attributes,
+};
 
 static struct android_usb_function *supported_functions[] = {
        &adb_function,
@@ -658,6 +720,7 @@ static struct android_usb_function *supported_functions[] = {
        &rndis_function,
        &mass_storage_function,
        &accessory_function,
+       &audio_source_function,
        NULL
 };
 
diff --git a/drivers/usb/gadget/f_audio_source.c b/drivers/usb/gadget/f_audio_source.c
new file mode 100644 (file)
index 0000000..c762543
--- /dev/null
@@ -0,0 +1,826 @@
+/*
+ * Gadget Function Driver for USB audio source device
+ *
+ * Copyright (C) 2012 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/usb/audio.h>
+#include <linux/wait.h>
+#include <sound/core.h>
+#include <sound/initval.h>
+#include <sound/pcm.h>
+
+#define SAMPLE_RATE 44100
+/* Each frame is two 16 bit integers (one per channel) */
+#define BYTES_PER_FRAME 4
+#define FRAMES_PER_MSEC (SAMPLE_RATE / 1000)
+/* Add one to FRAMES_PER_MSEC to adjust for round-off above */
+#define IN_EP_MAX_PACKET_SIZE ((FRAMES_PER_MSEC + 1) * BYTES_PER_FRAME)
+
+/* Number of requests to allocate */
+#define IN_EP_REQ_COUNT 16
+
+#define AUDIO_AC_INTERFACE     0
+#define AUDIO_AS_INTERFACE     1
+#define AUDIO_NUM_INTERFACES   2
+
+/* B.3.1  Standard AC Interface Descriptor */
+static struct usb_interface_descriptor ac_interface_desc = {
+       .bLength =              USB_DT_INTERFACE_SIZE,
+       .bDescriptorType =      USB_DT_INTERFACE,
+       .bNumEndpoints =        0,
+       .bInterfaceClass =      USB_CLASS_AUDIO,
+       .bInterfaceSubClass =   USB_SUBCLASS_AUDIOCONTROL,
+};
+
+DECLARE_UAC_AC_HEADER_DESCRIPTOR(2);
+
+#define UAC_DT_AC_HEADER_LENGTH        UAC_DT_AC_HEADER_SIZE(AUDIO_NUM_INTERFACES)
+/* 1 input terminal, 1 output terminal and 1 feature unit */
+#define UAC_DT_TOTAL_LENGTH (UAC_DT_AC_HEADER_LENGTH \
+       + UAC_DT_INPUT_TERMINAL_SIZE + UAC_DT_OUTPUT_TERMINAL_SIZE \
+       + UAC_DT_FEATURE_UNIT_SIZE(0))
+/* B.3.2  Class-Specific AC Interface Descriptor */
+static struct uac1_ac_header_descriptor_2 ac_header_desc = {
+       .bLength =              UAC_DT_AC_HEADER_LENGTH,
+       .bDescriptorType =      USB_DT_CS_INTERFACE,
+       .bDescriptorSubtype =   UAC_HEADER,
+       .bcdADC =               __constant_cpu_to_le16(0x0100),
+       .wTotalLength =         __constant_cpu_to_le16(UAC_DT_TOTAL_LENGTH),
+       .bInCollection =        AUDIO_NUM_INTERFACES,
+       .baInterfaceNr = {
+               [0] =           AUDIO_AC_INTERFACE,
+               [1] =           AUDIO_AS_INTERFACE,
+       }
+};
+
+#define INPUT_TERMINAL_ID      1
+static struct uac_input_terminal_descriptor input_terminal_desc = {
+       .bLength =              UAC_DT_INPUT_TERMINAL_SIZE,
+       .bDescriptorType =      USB_DT_CS_INTERFACE,
+       .bDescriptorSubtype =   UAC_INPUT_TERMINAL,
+       .bTerminalID =          INPUT_TERMINAL_ID,
+       .wTerminalType =        UAC_INPUT_TERMINAL_MICROPHONE,
+       .bAssocTerminal =       0,
+       .wChannelConfig =       0x3,
+};
+
+DECLARE_UAC_FEATURE_UNIT_DESCRIPTOR(0);
+
+#define FEATURE_UNIT_ID                2
+static struct uac_feature_unit_descriptor_0 feature_unit_desc = {
+       .bLength                = UAC_DT_FEATURE_UNIT_SIZE(0),
+       .bDescriptorType        = USB_DT_CS_INTERFACE,
+       .bDescriptorSubtype     = UAC_FEATURE_UNIT,
+       .bUnitID                = FEATURE_UNIT_ID,
+       .bSourceID              = INPUT_TERMINAL_ID,
+       .bControlSize           = 2,
+};
+
+#define OUTPUT_TERMINAL_ID     3
+static struct uac1_output_terminal_descriptor output_terminal_desc = {
+       .bLength                = UAC_DT_OUTPUT_TERMINAL_SIZE,
+       .bDescriptorType        = USB_DT_CS_INTERFACE,
+       .bDescriptorSubtype     = UAC_OUTPUT_TERMINAL,
+       .bTerminalID            = OUTPUT_TERMINAL_ID,
+       .wTerminalType          = UAC_TERMINAL_STREAMING,
+       .bAssocTerminal         = FEATURE_UNIT_ID,
+       .bSourceID              = FEATURE_UNIT_ID,
+};
+
+/* B.4.1  Standard AS Interface Descriptor */
+static struct usb_interface_descriptor as_interface_alt_0_desc = {
+       .bLength =              USB_DT_INTERFACE_SIZE,
+       .bDescriptorType =      USB_DT_INTERFACE,
+       .bAlternateSetting =    0,
+       .bNumEndpoints =        0,
+       .bInterfaceClass =      USB_CLASS_AUDIO,
+       .bInterfaceSubClass =   USB_SUBCLASS_AUDIOSTREAMING,
+};
+
+static struct usb_interface_descriptor as_interface_alt_1_desc = {
+       .bLength =              USB_DT_INTERFACE_SIZE,
+       .bDescriptorType =      USB_DT_INTERFACE,
+       .bAlternateSetting =    1,
+       .bNumEndpoints =        1,
+       .bInterfaceClass =      USB_CLASS_AUDIO,
+       .bInterfaceSubClass =   USB_SUBCLASS_AUDIOSTREAMING,
+};
+
+/* B.4.2  Class-Specific AS Interface Descriptor */
+static struct uac1_as_header_descriptor as_header_desc = {
+       .bLength =              UAC_DT_AS_HEADER_SIZE,
+       .bDescriptorType =      USB_DT_CS_INTERFACE,
+       .bDescriptorSubtype =   UAC_AS_GENERAL,
+       .bTerminalLink =        INPUT_TERMINAL_ID,
+       .bDelay =               1,
+       .wFormatTag =           UAC_FORMAT_TYPE_I_PCM,
+};
+
+DECLARE_UAC_FORMAT_TYPE_I_DISCRETE_DESC(1);
+
+static struct uac_format_type_i_discrete_descriptor_1 as_type_i_desc = {
+       .bLength =              UAC_FORMAT_TYPE_I_DISCRETE_DESC_SIZE(1),
+       .bDescriptorType =      USB_DT_CS_INTERFACE,
+       .bDescriptorSubtype =   UAC_FORMAT_TYPE,
+       .bFormatType =          UAC_FORMAT_TYPE_I,
+       .bSubframeSize =        2,
+       .bBitResolution =       16,
+       .bSamFreqType =         1,
+};
+
+/* Standard ISO IN Endpoint Descriptor for highspeed */
+static struct usb_endpoint_descriptor hs_as_in_ep_desc  = {
+       .bLength =              USB_DT_ENDPOINT_AUDIO_SIZE,
+       .bDescriptorType =      USB_DT_ENDPOINT,
+       .bEndpointAddress =     USB_DIR_IN,
+       .bmAttributes =         USB_ENDPOINT_SYNC_SYNC
+                               | USB_ENDPOINT_XFER_ISOC,
+       .wMaxPacketSize =       __constant_cpu_to_le16(IN_EP_MAX_PACKET_SIZE),
+       .bInterval =            4, /* poll 1 per millisecond */
+};
+
+/* Standard ISO IN Endpoint Descriptor for highspeed */
+static struct usb_endpoint_descriptor fs_as_in_ep_desc  = {
+       .bLength =              USB_DT_ENDPOINT_AUDIO_SIZE,
+       .bDescriptorType =      USB_DT_ENDPOINT,
+       .bEndpointAddress =     USB_DIR_IN,
+       .bmAttributes =         USB_ENDPOINT_SYNC_SYNC
+                               | USB_ENDPOINT_XFER_ISOC,
+       .wMaxPacketSize =       __constant_cpu_to_le16(IN_EP_MAX_PACKET_SIZE),
+       .bInterval =            1, /* poll 1 per millisecond */
+};
+
+/* Class-specific AS ISO OUT Endpoint Descriptor */
+static struct uac_iso_endpoint_descriptor as_iso_in_desc = {
+       .bLength =              UAC_ISO_ENDPOINT_DESC_SIZE,
+       .bDescriptorType =      USB_DT_CS_ENDPOINT,
+       .bDescriptorSubtype =   UAC_EP_GENERAL,
+       .bmAttributes =         1,
+       .bLockDelayUnits =      1,
+       .wLockDelay =           __constant_cpu_to_le16(1),
+};
+
+static struct usb_descriptor_header *hs_audio_desc[] = {
+       (struct usb_descriptor_header *)&ac_interface_desc,
+       (struct usb_descriptor_header *)&ac_header_desc,
+
+       (struct usb_descriptor_header *)&input_terminal_desc,
+       (struct usb_descriptor_header *)&output_terminal_desc,
+       (struct usb_descriptor_header *)&feature_unit_desc,
+
+       (struct usb_descriptor_header *)&as_interface_alt_0_desc,
+       (struct usb_descriptor_header *)&as_interface_alt_1_desc,
+       (struct usb_descriptor_header *)&as_header_desc,
+
+       (struct usb_descriptor_header *)&as_type_i_desc,
+
+       (struct usb_descriptor_header *)&hs_as_in_ep_desc,
+       (struct usb_descriptor_header *)&as_iso_in_desc,
+       NULL,
+};
+
+static struct usb_descriptor_header *fs_audio_desc[] = {
+       (struct usb_descriptor_header *)&ac_interface_desc,
+       (struct usb_descriptor_header *)&ac_header_desc,
+
+       (struct usb_descriptor_header *)&input_terminal_desc,
+       (struct usb_descriptor_header *)&output_terminal_desc,
+       (struct usb_descriptor_header *)&feature_unit_desc,
+
+       (struct usb_descriptor_header *)&as_interface_alt_0_desc,
+       (struct usb_descriptor_header *)&as_interface_alt_1_desc,
+       (struct usb_descriptor_header *)&as_header_desc,
+
+       (struct usb_descriptor_header *)&as_type_i_desc,
+
+       (struct usb_descriptor_header *)&fs_as_in_ep_desc,
+       (struct usb_descriptor_header *)&as_iso_in_desc,
+       NULL,
+};
+
+static struct snd_pcm_hardware audio_hw_info = {
+       .info =                 SNDRV_PCM_INFO_MMAP |
+                               SNDRV_PCM_INFO_MMAP_VALID |
+                               SNDRV_PCM_INFO_BATCH |
+                               SNDRV_PCM_INFO_INTERLEAVED |
+                               SNDRV_PCM_INFO_BLOCK_TRANSFER,
+
+       .formats                = SNDRV_PCM_FMTBIT_S16_LE,
+       .channels_min           = 2,
+       .channels_max           = 2,
+       .rate_min               = SAMPLE_RATE,
+       .rate_max               = SAMPLE_RATE,
+
+       .buffer_bytes_max =     1024 * 1024,
+       .period_bytes_min =     64,
+       .period_bytes_max =     512 * 1024,
+       .periods_min =          2,
+       .periods_max =          1024,
+};
+
+/*-------------------------------------------------------------------------*/
+
+struct audio_source_config {
+       int     card;
+       int     device;
+};
+
+struct audio_dev {
+       struct usb_function             func;
+       struct snd_card                 *card;
+       struct snd_pcm                  *pcm;
+       struct snd_pcm_substream *substream;
+
+       struct list_head                idle_reqs;
+       struct usb_ep                   *in_ep;
+       struct usb_endpoint_descriptor  *in_desc;
+
+       spinlock_t                      lock;
+
+       /* beginning, end and current position in our buffer */
+       void                            *buffer_start;
+       void                            *buffer_end;
+       void                            *buffer_pos;
+
+       /* byte size of a "period" */
+       unsigned int                    period;
+       /* bytes sent since last call to snd_pcm_period_elapsed */
+       unsigned int                    period_offset;
+       /* time we started playing */
+       ktime_t                         start_time;
+       /* number of frames sent since start_time */
+       s64                             frames_sent;
+};
+
+static inline struct audio_dev *func_to_audio(struct usb_function *f)
+{
+       return container_of(f, struct audio_dev, func);
+}
+
+/*-------------------------------------------------------------------------*/
+
+static struct usb_request *audio_request_new(struct usb_ep *ep, int buffer_size)
+{
+       struct usb_request *req = usb_ep_alloc_request(ep, GFP_KERNEL);
+       if (!req)
+               return NULL;
+
+       req->buf = kmalloc(buffer_size, GFP_KERNEL);
+       if (!req->buf) {
+               usb_ep_free_request(ep, req);
+               return NULL;
+       }
+       req->length = buffer_size;
+       return req;
+}
+
+static void audio_request_free(struct usb_request *req, struct usb_ep *ep)
+{
+       if (req) {
+               kfree(req->buf);
+               usb_ep_free_request(ep, req);
+       }
+}
+
+static void audio_req_put(struct audio_dev *audio, struct usb_request *req)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&audio->lock, flags);
+       list_add_tail(&req->list, &audio->idle_reqs);
+       spin_unlock_irqrestore(&audio->lock, flags);
+}
+
+static struct usb_request *audio_req_get(struct audio_dev *audio)
+{
+       unsigned long flags;
+       struct usb_request *req;
+
+       spin_lock_irqsave(&audio->lock, flags);
+       if (list_empty(&audio->idle_reqs)) {
+               req = 0;
+       } else {
+               req = list_first_entry(&audio->idle_reqs, struct usb_request,
+                               list);
+               list_del(&req->list);
+       }
+       spin_unlock_irqrestore(&audio->lock, flags);
+       return req;
+}
+
+/* send the appropriate number of packets to match our bitrate */
+static void audio_send(struct audio_dev *audio)
+{
+       struct snd_pcm_runtime *runtime;
+       struct usb_request *req;
+       int length, length1, length2, ret;
+       s64 msecs;
+       s64 frames;
+       ktime_t now;
+
+       /* audio->substream will be null if we have been closed */
+       if (!audio->substream)
+               return;
+       /* audio->buffer_pos will be null if we have been stopped */
+       if (!audio->buffer_pos)
+               return;
+
+       runtime = audio->substream->runtime;
+
+       now = ktime_get();
+       msecs = ktime_to_ns(now) - ktime_to_ns(audio->start_time);
+       do_div(msecs, 1000000);
+       /* Add a bit to msecs so we queue some extra requests in case
+        * we miss a few SOFs due to interrupts being disabled or CPU load.
+        */
+       msecs += IN_EP_REQ_COUNT/2;
+       frames = msecs * SAMPLE_RATE;
+       do_div(frames, 1000);
+
+       /* Readjust our frames_sent if we fall too far behind.
+        * If we get too far behind it is better to drop some frames than
+        * to keep sending data too fast in an attempt to catch up.
+        */
+       if (frames - audio->frames_sent > 2 * FRAMES_PER_MSEC * IN_EP_REQ_COUNT)
+               audio->frames_sent = frames - FRAMES_PER_MSEC;
+
+       frames -= audio->frames_sent;
+
+       while (frames > 0) {
+               req = audio_req_get(audio);
+               if (!req)
+                       break;
+
+               length = frames_to_bytes(runtime, frames);
+               if (length > IN_EP_MAX_PACKET_SIZE)
+                       length = IN_EP_MAX_PACKET_SIZE;
+
+               if (audio->buffer_pos + length > audio->buffer_end)
+                       length1 = audio->buffer_end - audio->buffer_pos;
+               else
+                       length1 = length;
+               memcpy(req->buf, audio->buffer_pos, length1);
+               if (length1 < length) {
+                       /* Wrap around and copy remaining length
+                        * at beginning of buffer.
+                        */
+                       length2 = length - length1;
+                       memcpy(req->buf + length1, audio->buffer_start,
+                                       length2);
+                       audio->buffer_pos = audio->buffer_start + length2;
+               } else {
+                       audio->buffer_pos += length1;
+                       if (audio->buffer_pos >= audio->buffer_end)
+                               audio->buffer_pos = audio->buffer_start;
+               }
+
+               req->length = length;
+               ret = usb_ep_queue(audio->in_ep, req, GFP_ATOMIC);
+               if (ret < 0) {
+                       pr_err("usb_ep_queue failed ret: %d\n", ret);
+                       audio_req_put(audio, req);
+                       break;
+               }
+
+               frames -= bytes_to_frames(runtime, length);
+               audio->frames_sent += bytes_to_frames(runtime, length);
+       }
+}
+
+static void audio_control_complete(struct usb_ep *ep, struct usb_request *req)
+{
+       /* nothing to do here */
+}
+
+static void audio_data_complete(struct usb_ep *ep, struct usb_request *req)
+{
+       struct audio_dev *audio = req->context;
+
+       pr_debug("audio_data_complete req->status %d req->actual %d\n",
+               req->status, req->actual);
+
+       audio_req_put(audio, req);
+
+       if (!audio->buffer_start)
+               return;
+
+       audio->period_offset += req->actual;
+       if (audio->period_offset >= audio->period) {
+               snd_pcm_period_elapsed(audio->substream);
+               audio->period_offset = 0;
+       }
+       audio_send(audio);
+}
+
+static int audio_set_endpoint_req(struct usb_function *f,
+               const struct usb_ctrlrequest *ctrl)
+{
+       int value = -EOPNOTSUPP;
+       u16 ep = le16_to_cpu(ctrl->wIndex);
+       u16 len = le16_to_cpu(ctrl->wLength);
+       u16 w_value = le16_to_cpu(ctrl->wValue);
+
+       pr_debug("bRequest 0x%x, w_value 0x%04x, len %d, endpoint %d\n",
+                       ctrl->bRequest, w_value, len, ep);
+
+       switch (ctrl->bRequest) {
+       case UAC_SET_CUR:
+       case UAC_SET_MIN:
+       case UAC_SET_MAX:
+       case UAC_SET_RES:
+               value = len;
+               break;
+       default:
+               break;
+       }
+
+       return value;
+}
+
+static int audio_get_endpoint_req(struct usb_function *f,
+               const struct usb_ctrlrequest *ctrl)
+{
+       struct usb_composite_dev *cdev = f->config->cdev;
+       int value = -EOPNOTSUPP;
+       u8 ep = ((le16_to_cpu(ctrl->wIndex) >> 8) & 0xFF);
+       u16 len = le16_to_cpu(ctrl->wLength);
+       u16 w_value = le16_to_cpu(ctrl->wValue);
+       u8 *buf = cdev->req->buf;
+
+       pr_debug("bRequest 0x%x, w_value 0x%04x, len %d, endpoint %d\n",
+                       ctrl->bRequest, w_value, len, ep);
+
+       if (w_value == UAC_EP_CS_ATTR_SAMPLE_RATE << 8) {
+               switch (ctrl->bRequest) {
+               case UAC_GET_CUR:
+               case UAC_GET_MIN:
+               case UAC_GET_MAX:
+               case UAC_GET_RES:
+                       /* return our sample rate */
+                       buf[0] = (u8)SAMPLE_RATE;
+                       buf[1] = (u8)(SAMPLE_RATE >> 8);
+                       buf[2] = (u8)(SAMPLE_RATE >> 16);
+                       value = 3;
+                       break;
+               default:
+                       break;
+               }
+       }
+
+       return value;
+}
+
+static int
+audio_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
+{
+       struct usb_composite_dev *cdev = f->config->cdev;
+       struct usb_request *req = cdev->req;
+       int value = -EOPNOTSUPP;
+       u16 w_index = le16_to_cpu(ctrl->wIndex);
+       u16 w_value = le16_to_cpu(ctrl->wValue);
+       u16 w_length = le16_to_cpu(ctrl->wLength);
+
+       /* composite driver infrastructure handles everything; interface
+        * activation uses set_alt().
+        */
+       switch (ctrl->bRequestType) {
+       case USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_ENDPOINT:
+               value = audio_set_endpoint_req(f, ctrl);
+               break;
+
+       case USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_ENDPOINT:
+               value = audio_get_endpoint_req(f, ctrl);
+               break;
+       }
+
+       /* respond with data transfer or status phase? */
+       if (value >= 0) {
+               pr_debug("audio req%02x.%02x v%04x i%04x l%d\n",
+                       ctrl->bRequestType, ctrl->bRequest,
+                       w_value, w_index, w_length);
+               req->zero = 0;
+               req->length = value;
+               req->complete = audio_control_complete;
+               value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
+               if (value < 0)
+                       pr_err("audio response on err %d\n", value);
+       }
+
+       /* device either stalls (value < 0) or reports success */
+       return value;
+}
+
+static int audio_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
+{
+       struct audio_dev *audio = func_to_audio(f);
+       struct usb_composite_dev *cdev = f->config->cdev;
+
+       pr_debug("audio_set_alt intf %d, alt %d\n", intf, alt);
+       config_ep_by_speed(cdev->gadget, f, audio->in_ep);
+       usb_ep_enable(audio->in_ep);
+       return 0;
+}
+
+static void audio_disable(struct usb_function *f)
+{
+       struct audio_dev        *audio = func_to_audio(f);
+
+       pr_debug("audio_disable\n");
+       usb_ep_disable(audio->in_ep);
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void audio_build_desc(struct audio_dev *audio)
+{
+       u8 *sam_freq;
+       int rate;
+
+       /* Set channel numbers */
+       input_terminal_desc.bNrChannels = 2;
+       as_type_i_desc.bNrChannels = 2;
+
+       /* Set sample rates */
+       rate = SAMPLE_RATE;
+       sam_freq = as_type_i_desc.tSamFreq[0];
+       memcpy(sam_freq, &rate, 3);
+}
+
+/* audio function driver setup/binding */
+static int
+audio_bind(struct usb_configuration *c, struct usb_function *f)
+{
+       struct usb_composite_dev *cdev = c->cdev;
+       struct audio_dev *audio = func_to_audio(f);
+       int status;
+       struct usb_ep *ep;
+       struct usb_request *req;
+       int i;
+
+       audio_build_desc(audio);
+
+       /* allocate instance-specific interface IDs, and patch descriptors */
+       status = usb_interface_id(c, f);
+       if (status < 0)
+               goto fail;
+       ac_interface_desc.bInterfaceNumber = status;
+
+       status = usb_interface_id(c, f);
+       if (status < 0)
+               goto fail;
+       as_interface_alt_0_desc.bInterfaceNumber = status;
+       as_interface_alt_1_desc.bInterfaceNumber = status;
+
+       status = -ENODEV;
+
+       /* allocate our endpoint */
+       ep = usb_ep_autoconfig(cdev->gadget, &fs_as_in_ep_desc);
+       if (!ep)
+               goto fail;
+       audio->in_ep = ep;
+       ep->driver_data = audio; /* claim */
+
+       if (gadget_is_dualspeed(c->cdev->gadget))
+               hs_as_in_ep_desc.bEndpointAddress =
+                       fs_as_in_ep_desc.bEndpointAddress;
+
+       f->descriptors = fs_audio_desc;
+       f->hs_descriptors = hs_audio_desc;
+
+       for (i = 0, status = 0; i < IN_EP_REQ_COUNT && status == 0; i++) {
+               req = audio_request_new(ep, IN_EP_MAX_PACKET_SIZE);
+               if (req) {
+                       req->context = audio;
+                       req->complete = audio_data_complete;
+                       audio_req_put(audio, req);
+               } else
+                       status = -ENOMEM;
+       }
+
+fail:
+       return status;
+}
+
+static void
+audio_unbind(struct usb_configuration *c, struct usb_function *f)
+{
+       struct audio_dev *audio = func_to_audio(f);
+       struct usb_request *req;
+
+       while ((req = audio_req_get(audio)))
+               audio_request_free(req, audio->in_ep);
+
+       snd_card_free_when_closed(audio->card);
+       kfree(audio);
+}
+
+static void audio_pcm_playback_start(struct audio_dev *audio)
+{
+       audio->start_time = ktime_get();
+       audio->frames_sent = 0;
+       audio_send(audio);
+}
+
+static void audio_pcm_playback_stop(struct audio_dev *audio)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&audio->lock, flags);
+       audio->buffer_start = 0;
+       audio->buffer_end = 0;
+       audio->buffer_pos = 0;
+       spin_unlock_irqrestore(&audio->lock, flags);
+}
+
+static int audio_pcm_open(struct snd_pcm_substream *substream)
+{
+       struct snd_pcm_runtime *runtime = substream->runtime;
+       struct audio_dev *audio = substream->private_data;
+
+       runtime->private_data = audio;
+       runtime->hw = audio_hw_info;
+       snd_pcm_limit_hw_rates(runtime);
+       runtime->hw.channels_max = 2;
+
+       audio->substream = substream;
+       return 0;
+}
+
+static int audio_pcm_close(struct snd_pcm_substream *substream)
+{
+       struct audio_dev *audio = substream->private_data;
+       unsigned long flags;
+
+       spin_lock_irqsave(&audio->lock, flags);
+       audio->substream = NULL;
+       spin_unlock_irqrestore(&audio->lock, flags);
+
+       return 0;
+}
+
+static int audio_pcm_hw_params(struct snd_pcm_substream *substream,
+                               struct snd_pcm_hw_params *params)
+{
+       unsigned int channels = params_channels(params);
+       unsigned int rate = params_rate(params);
+
+       if (rate != SAMPLE_RATE)
+               return -EINVAL;
+       if (channels != 2)
+               return -EINVAL;
+
+       return snd_pcm_lib_alloc_vmalloc_buffer(substream,
+               params_buffer_bytes(params));
+}
+
+static int audio_pcm_hw_free(struct snd_pcm_substream *substream)
+{
+       return snd_pcm_lib_free_vmalloc_buffer(substream);
+}
+
+static int audio_pcm_prepare(struct snd_pcm_substream *substream)
+{
+       struct snd_pcm_runtime *runtime = substream->runtime;
+       struct audio_dev *audio = runtime->private_data;
+
+       audio->period = snd_pcm_lib_period_bytes(substream);
+       audio->period_offset = 0;
+       audio->buffer_start = runtime->dma_area;
+       audio->buffer_end = audio->buffer_start
+               + snd_pcm_lib_buffer_bytes(substream);
+       audio->buffer_pos = audio->buffer_start;
+
+       return 0;
+}
+
+static snd_pcm_uframes_t audio_pcm_pointer(struct snd_pcm_substream *substream)
+{
+       struct snd_pcm_runtime *runtime = substream->runtime;
+       struct audio_dev *audio = runtime->private_data;
+       ssize_t bytes = audio->buffer_pos - audio->buffer_start;
+
+       /* return offset of next frame to fill in our buffer */
+       return bytes_to_frames(runtime, bytes);
+}
+
+static int audio_pcm_playback_trigger(struct snd_pcm_substream *substream,
+                                       int cmd)
+{
+       struct audio_dev *audio = substream->runtime->private_data;
+       int ret = 0;
+
+       switch (cmd) {
+       case SNDRV_PCM_TRIGGER_START:
+       case SNDRV_PCM_TRIGGER_RESUME:
+               audio_pcm_playback_start(audio);
+               break;
+
+       case SNDRV_PCM_TRIGGER_STOP:
+       case SNDRV_PCM_TRIGGER_SUSPEND:
+               audio_pcm_playback_stop(audio);
+               break;
+
+       default:
+               ret = -EINVAL;
+       }
+
+       return ret;
+}
+
+static struct snd_pcm_ops audio_playback_ops = {
+       .open           = audio_pcm_open,
+       .close          = audio_pcm_close,
+       .ioctl          = snd_pcm_lib_ioctl,
+       .hw_params      = audio_pcm_hw_params,
+       .hw_free        = audio_pcm_hw_free,
+       .prepare        = audio_pcm_prepare,
+       .trigger        = audio_pcm_playback_trigger,
+       .pointer        = audio_pcm_pointer,
+};
+
+int audio_source_bind_config(struct usb_configuration *c,
+               struct audio_source_config *config)
+{
+       struct audio_dev *audio;
+       struct snd_card *card;
+       struct snd_pcm *pcm;
+       int err;
+
+       config->card = -1;
+       config->device = -1;
+
+       audio = kzalloc(sizeof *audio, GFP_KERNEL);
+       if (!audio)
+               return -ENOMEM;
+
+       audio->func.name = "audio_source";
+
+       spin_lock_init(&audio->lock);
+
+       audio->func.bind = audio_bind;
+       audio->func.unbind = audio_unbind;
+       audio->func.set_alt = audio_set_alt;
+       audio->func.setup = audio_setup;
+       audio->func.disable = audio_disable;
+       audio->in_desc = &fs_as_in_ep_desc;
+
+       INIT_LIST_HEAD(&audio->idle_reqs);
+
+       err = snd_card_create(SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1,
+                       THIS_MODULE, 0, &card);
+       if (err)
+               goto snd_card_fail;
+
+       snd_card_set_dev(card, &c->cdev->gadget->dev);
+
+       err = snd_pcm_new(card, "USB audio source", 0, 1, 0, &pcm);
+       if (err)
+               goto pcm_fail;
+       pcm->private_data = audio;
+       pcm->info_flags = 0;
+       audio->pcm = pcm;
+
+       strlcpy(pcm->name, "USB gadget audio", sizeof(pcm->name));
+
+       snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &audio_playback_ops);
+       snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV,
+                               NULL, 0, 64 * 1024);
+
+       strlcpy(card->driver, "audio_source", sizeof(card->driver));
+       strlcpy(card->shortname, card->driver, sizeof(card->shortname));
+       strlcpy(card->longname, "USB accessory audio source",
+               sizeof(card->longname));
+
+       err = snd_card_register(card);
+       if (err)
+               goto register_fail;
+
+       err = usb_add_function(c, &audio->func);
+       if (err)
+               goto add_fail;
+
+       config->card = pcm->card->number;
+       config->device = pcm->device;
+       audio->card = card;
+       return 0;
+
+add_fail:
+register_fail:
+pcm_fail:
+       snd_card_free(audio->card);
+snd_card_fail:
+       kfree(audio);
+       return err;
+}