stmmac: priv->lock can be used uninitialized
[linux-2.6.git] / drivers / spi / spidev.c
1 /*
2  * spidev.c -- simple synchronous userspace interface to SPI devices
3  *
4  * Copyright (C) 2006 SWAPP
5  *      Andrea Paterniani <a.paterniani@swapp-eng.it>
6  * Copyright (C) 2007 David Brownell (simplification, cleanup)
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License as published by
10  * the Free Software Foundation; either version 2 of the License, or
11  * (at your option) any later version.
12  *
13  * This program is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16  * GNU General Public License for more details.
17  *
18  * You should have received a copy of the GNU General Public License
19  * along with this program; if not, write to the Free Software
20  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21  */
22
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/ioctl.h>
26 #include <linux/fs.h>
27 #include <linux/device.h>
28 #include <linux/err.h>
29 #include <linux/list.h>
30 #include <linux/errno.h>
31 #include <linux/mutex.h>
32 #include <linux/slab.h>
33
34 #include <linux/spi/spi.h>
35 #include <linux/spi/spidev.h>
36
37 #include <asm/uaccess.h>
38
39
40 /*
41  * This supports acccess to SPI devices using normal userspace I/O calls.
42  * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
43  * and often mask message boundaries, full SPI support requires full duplex
44  * transfers.  There are several kinds of internal message boundaries to
45  * handle chipselect management and other protocol options.
46  *
47  * SPI has a character major number assigned.  We allocate minor numbers
48  * dynamically using a bitmask.  You must use hotplug tools, such as udev
49  * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
50  * nodes, since there is no fixed association of minor numbers with any
51  * particular SPI bus or device.
52  */
53 #define SPIDEV_MAJOR                    153     /* assigned */
54 #define N_SPI_MINORS                    32      /* ... up to 256 */
55
56 static DECLARE_BITMAP(minors, N_SPI_MINORS);
57
58
59 /* Bit masks for spi_device.mode management.  Note that incorrect
60  * settings for some settings can cause *lots* of trouble for other
61  * devices on a shared bus:
62  *
63  *  - CS_HIGH ... this device will be active when it shouldn't be
64  *  - 3WIRE ... when active, it won't behave as it should
65  *  - NO_CS ... there will be no explicit message boundaries; this
66  *      is completely incompatible with the shared bus model
67  *  - READY ... transfers may proceed when they shouldn't.
68  *
69  * REVISIT should changing those flags be privileged?
70  */
71 #define SPI_MODE_MASK           (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
72                                 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \
73                                 | SPI_NO_CS | SPI_READY)
74
75 struct spidev_data {
76         dev_t                   devt;
77         spinlock_t              spi_lock;
78         struct spi_device       *spi;
79         struct list_head        device_entry;
80
81         /* buffer is NULL unless this device is open (users > 0) */
82         struct mutex            buf_lock;
83         unsigned                users;
84         u8                      *buffer;
85 };
86
87 static LIST_HEAD(device_list);
88 static DEFINE_MUTEX(device_list_lock);
89
90 static unsigned bufsiz = 4096;
91 module_param(bufsiz, uint, S_IRUGO);
92 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
93
94 /*-------------------------------------------------------------------------*/
95
96 /*
97  * We can't use the standard synchronous wrappers for file I/O; we
98  * need to protect against async removal of the underlying spi_device.
99  */
100 static void spidev_complete(void *arg)
101 {
102         complete(arg);
103 }
104
105 static ssize_t
106 spidev_sync(struct spidev_data *spidev, struct spi_message *message)
107 {
108         DECLARE_COMPLETION_ONSTACK(done);
109         int status;
110
111         message->complete = spidev_complete;
112         message->context = &done;
113
114         spin_lock_irq(&spidev->spi_lock);
115         if (spidev->spi == NULL)
116                 status = -ESHUTDOWN;
117         else
118                 status = spi_async(spidev->spi, message);
119         spin_unlock_irq(&spidev->spi_lock);
120
121         if (status == 0) {
122                 wait_for_completion(&done);
123                 status = message->status;
124                 if (status == 0)
125                         status = message->actual_length;
126         }
127         return status;
128 }
129
130 static inline ssize_t
131 spidev_sync_write(struct spidev_data *spidev, size_t len)
132 {
133         struct spi_transfer     t = {
134                         .tx_buf         = spidev->buffer,
135                         .len            = len,
136                 };
137         struct spi_message      m;
138
139         spi_message_init(&m);
140         spi_message_add_tail(&t, &m);
141         return spidev_sync(spidev, &m);
142 }
143
144 static inline ssize_t
145 spidev_sync_read(struct spidev_data *spidev, size_t len)
146 {
147         struct spi_transfer     t = {
148                         .rx_buf         = spidev->buffer,
149                         .len            = len,
150                 };
151         struct spi_message      m;
152
153         spi_message_init(&m);
154         spi_message_add_tail(&t, &m);
155         return spidev_sync(spidev, &m);
156 }
157
158 /*-------------------------------------------------------------------------*/
159
160 /* Read-only message with current device setup */
161 static ssize_t
162 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
163 {
164         struct spidev_data      *spidev;
165         ssize_t                 status = 0;
166
167         /* chipselect only toggles at start or end of operation */
168         if (count > bufsiz)
169                 return -EMSGSIZE;
170
171         spidev = filp->private_data;
172
173         mutex_lock(&spidev->buf_lock);
174         status = spidev_sync_read(spidev, count);
175         if (status > 0) {
176                 unsigned long   missing;
177
178                 missing = copy_to_user(buf, spidev->buffer, status);
179                 if (missing == status)
180                         status = -EFAULT;
181                 else
182                         status = status - missing;
183         }
184         mutex_unlock(&spidev->buf_lock);
185
186         return status;
187 }
188
189 /* Write-only message with current device setup */
190 static ssize_t
191 spidev_write(struct file *filp, const char __user *buf,
192                 size_t count, loff_t *f_pos)
193 {
194         struct spidev_data      *spidev;
195         ssize_t                 status = 0;
196         unsigned long           missing;
197
198         /* chipselect only toggles at start or end of operation */
199         if (count > bufsiz)
200                 return -EMSGSIZE;
201
202         spidev = filp->private_data;
203
204         mutex_lock(&spidev->buf_lock);
205         missing = copy_from_user(spidev->buffer, buf, count);
206         if (missing == 0) {
207                 status = spidev_sync_write(spidev, count);
208         } else
209                 status = -EFAULT;
210         mutex_unlock(&spidev->buf_lock);
211
212         return status;
213 }
214
215 static int spidev_message(struct spidev_data *spidev,
216                 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
217 {
218         struct spi_message      msg;
219         struct spi_transfer     *k_xfers;
220         struct spi_transfer     *k_tmp;
221         struct spi_ioc_transfer *u_tmp;
222         unsigned                n, total;
223         u8                      *buf;
224         int                     status = -EFAULT;
225
226         spi_message_init(&msg);
227         k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
228         if (k_xfers == NULL)
229                 return -ENOMEM;
230
231         /* Construct spi_message, copying any tx data to bounce buffer.
232          * We walk the array of user-provided transfers, using each one
233          * to initialize a kernel version of the same transfer.
234          */
235         buf = spidev->buffer;
236         total = 0;
237         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
238                         n;
239                         n--, k_tmp++, u_tmp++) {
240                 k_tmp->len = u_tmp->len;
241
242                 total += k_tmp->len;
243                 if (total > bufsiz) {
244                         status = -EMSGSIZE;
245                         goto done;
246                 }
247
248                 if (u_tmp->rx_buf) {
249                         k_tmp->rx_buf = buf;
250                         if (!access_ok(VERIFY_WRITE, (u8 __user *)
251                                                 (uintptr_t) u_tmp->rx_buf,
252                                                 u_tmp->len))
253                                 goto done;
254                 }
255                 if (u_tmp->tx_buf) {
256                         k_tmp->tx_buf = buf;
257                         if (copy_from_user(buf, (const u8 __user *)
258                                                 (uintptr_t) u_tmp->tx_buf,
259                                         u_tmp->len))
260                                 goto done;
261                 }
262                 buf += k_tmp->len;
263
264                 k_tmp->cs_change = !!u_tmp->cs_change;
265                 k_tmp->bits_per_word = u_tmp->bits_per_word;
266                 k_tmp->delay_usecs = u_tmp->delay_usecs;
267                 k_tmp->speed_hz = u_tmp->speed_hz;
268 #ifdef VERBOSE
269                 dev_dbg(&spidev->spi->dev,
270                         "  xfer len %zd %s%s%s%dbits %u usec %uHz\n",
271                         u_tmp->len,
272                         u_tmp->rx_buf ? "rx " : "",
273                         u_tmp->tx_buf ? "tx " : "",
274                         u_tmp->cs_change ? "cs " : "",
275                         u_tmp->bits_per_word ? : spidev->spi->bits_per_word,
276                         u_tmp->delay_usecs,
277                         u_tmp->speed_hz ? : spidev->spi->max_speed_hz);
278 #endif
279                 spi_message_add_tail(k_tmp, &msg);
280         }
281
282         status = spidev_sync(spidev, &msg);
283         if (status < 0)
284                 goto done;
285
286         /* copy any rx data out of bounce buffer */
287         buf = spidev->buffer;
288         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
289                 if (u_tmp->rx_buf) {
290                         if (__copy_to_user((u8 __user *)
291                                         (uintptr_t) u_tmp->rx_buf, buf,
292                                         u_tmp->len)) {
293                                 status = -EFAULT;
294                                 goto done;
295                         }
296                 }
297                 buf += u_tmp->len;
298         }
299         status = total;
300
301 done:
302         kfree(k_xfers);
303         return status;
304 }
305
306 static long
307 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
308 {
309         int                     err = 0;
310         int                     retval = 0;
311         struct spidev_data      *spidev;
312         struct spi_device       *spi;
313         u32                     tmp;
314         unsigned                n_ioc;
315         struct spi_ioc_transfer *ioc;
316
317         /* Check type and command number */
318         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
319                 return -ENOTTY;
320
321         /* Check access direction once here; don't repeat below.
322          * IOC_DIR is from the user perspective, while access_ok is
323          * from the kernel perspective; so they look reversed.
324          */
325         if (_IOC_DIR(cmd) & _IOC_READ)
326                 err = !access_ok(VERIFY_WRITE,
327                                 (void __user *)arg, _IOC_SIZE(cmd));
328         if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
329                 err = !access_ok(VERIFY_READ,
330                                 (void __user *)arg, _IOC_SIZE(cmd));
331         if (err)
332                 return -EFAULT;
333
334         /* guard against device removal before, or while,
335          * we issue this ioctl.
336          */
337         spidev = filp->private_data;
338         spin_lock_irq(&spidev->spi_lock);
339         spi = spi_dev_get(spidev->spi);
340         spin_unlock_irq(&spidev->spi_lock);
341
342         if (spi == NULL)
343                 return -ESHUTDOWN;
344
345         /* use the buffer lock here for triple duty:
346          *  - prevent I/O (from us) so calling spi_setup() is safe;
347          *  - prevent concurrent SPI_IOC_WR_* from morphing
348          *    data fields while SPI_IOC_RD_* reads them;
349          *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
350          */
351         mutex_lock(&spidev->buf_lock);
352
353         switch (cmd) {
354         /* read requests */
355         case SPI_IOC_RD_MODE:
356                 retval = __put_user(spi->mode & SPI_MODE_MASK,
357                                         (__u8 __user *)arg);
358                 break;
359         case SPI_IOC_RD_LSB_FIRST:
360                 retval = __put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
361                                         (__u8 __user *)arg);
362                 break;
363         case SPI_IOC_RD_BITS_PER_WORD:
364                 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
365                 break;
366         case SPI_IOC_RD_MAX_SPEED_HZ:
367                 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg);
368                 break;
369
370         /* write requests */
371         case SPI_IOC_WR_MODE:
372                 retval = __get_user(tmp, (u8 __user *)arg);
373                 if (retval == 0) {
374                         u8      save = spi->mode;
375
376                         if (tmp & ~SPI_MODE_MASK) {
377                                 retval = -EINVAL;
378                                 break;
379                         }
380
381                         tmp |= spi->mode & ~SPI_MODE_MASK;
382                         spi->mode = (u8)tmp;
383                         retval = spi_setup(spi);
384                         if (retval < 0)
385                                 spi->mode = save;
386                         else
387                                 dev_dbg(&spi->dev, "spi mode %02x\n", tmp);
388                 }
389                 break;
390         case SPI_IOC_WR_LSB_FIRST:
391                 retval = __get_user(tmp, (__u8 __user *)arg);
392                 if (retval == 0) {
393                         u8      save = spi->mode;
394
395                         if (tmp)
396                                 spi->mode |= SPI_LSB_FIRST;
397                         else
398                                 spi->mode &= ~SPI_LSB_FIRST;
399                         retval = spi_setup(spi);
400                         if (retval < 0)
401                                 spi->mode = save;
402                         else
403                                 dev_dbg(&spi->dev, "%csb first\n",
404                                                 tmp ? 'l' : 'm');
405                 }
406                 break;
407         case SPI_IOC_WR_BITS_PER_WORD:
408                 retval = __get_user(tmp, (__u8 __user *)arg);
409                 if (retval == 0) {
410                         u8      save = spi->bits_per_word;
411
412                         spi->bits_per_word = tmp;
413                         retval = spi_setup(spi);
414                         if (retval < 0)
415                                 spi->bits_per_word = save;
416                         else
417                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
418                 }
419                 break;
420         case SPI_IOC_WR_MAX_SPEED_HZ:
421                 retval = __get_user(tmp, (__u32 __user *)arg);
422                 if (retval == 0) {
423                         u32     save = spi->max_speed_hz;
424
425                         spi->max_speed_hz = tmp;
426                         retval = spi_setup(spi);
427                         if (retval < 0)
428                                 spi->max_speed_hz = save;
429                         else
430                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
431                 }
432                 break;
433
434         default:
435                 /* segmented and/or full-duplex I/O request */
436                 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
437                                 || _IOC_DIR(cmd) != _IOC_WRITE) {
438                         retval = -ENOTTY;
439                         break;
440                 }
441
442                 tmp = _IOC_SIZE(cmd);
443                 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) {
444                         retval = -EINVAL;
445                         break;
446                 }
447                 n_ioc = tmp / sizeof(struct spi_ioc_transfer);
448                 if (n_ioc == 0)
449                         break;
450
451                 /* copy into scratch area */
452                 ioc = kmalloc(tmp, GFP_KERNEL);
453                 if (!ioc) {
454                         retval = -ENOMEM;
455                         break;
456                 }
457                 if (__copy_from_user(ioc, (void __user *)arg, tmp)) {
458                         kfree(ioc);
459                         retval = -EFAULT;
460                         break;
461                 }
462
463                 /* translate to spi_message, execute */
464                 retval = spidev_message(spidev, ioc, n_ioc);
465                 kfree(ioc);
466                 break;
467         }
468
469         mutex_unlock(&spidev->buf_lock);
470         spi_dev_put(spi);
471         return retval;
472 }
473
474 static int spidev_open(struct inode *inode, struct file *filp)
475 {
476         struct spidev_data      *spidev;
477         int                     status = -ENXIO;
478
479         mutex_lock(&device_list_lock);
480
481         list_for_each_entry(spidev, &device_list, device_entry) {
482                 if (spidev->devt == inode->i_rdev) {
483                         status = 0;
484                         break;
485                 }
486         }
487         if (status == 0) {
488                 if (!spidev->buffer) {
489                         spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
490                         if (!spidev->buffer) {
491                                 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
492                                 status = -ENOMEM;
493                         }
494                 }
495                 if (status == 0) {
496                         spidev->users++;
497                         filp->private_data = spidev;
498                         nonseekable_open(inode, filp);
499                 }
500         } else
501                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
502
503         mutex_unlock(&device_list_lock);
504         return status;
505 }
506
507 static int spidev_release(struct inode *inode, struct file *filp)
508 {
509         struct spidev_data      *spidev;
510         int                     status = 0;
511
512         mutex_lock(&device_list_lock);
513         spidev = filp->private_data;
514         filp->private_data = NULL;
515
516         /* last close? */
517         spidev->users--;
518         if (!spidev->users) {
519                 int             dofree;
520
521                 kfree(spidev->buffer);
522                 spidev->buffer = NULL;
523
524                 /* ... after we unbound from the underlying device? */
525                 spin_lock_irq(&spidev->spi_lock);
526                 dofree = (spidev->spi == NULL);
527                 spin_unlock_irq(&spidev->spi_lock);
528
529                 if (dofree)
530                         kfree(spidev);
531         }
532         mutex_unlock(&device_list_lock);
533
534         return status;
535 }
536
537 static const struct file_operations spidev_fops = {
538         .owner =        THIS_MODULE,
539         /* REVISIT switch to aio primitives, so that userspace
540          * gets more complete API coverage.  It'll simplify things
541          * too, except for the locking.
542          */
543         .write =        spidev_write,
544         .read =         spidev_read,
545         .unlocked_ioctl = spidev_ioctl,
546         .open =         spidev_open,
547         .release =      spidev_release,
548         .llseek =       no_llseek,
549 };
550
551 /*-------------------------------------------------------------------------*/
552
553 /* The main reason to have this class is to make mdev/udev create the
554  * /dev/spidevB.C character device nodes exposing our userspace API.
555  * It also simplifies memory management.
556  */
557
558 static struct class *spidev_class;
559
560 /*-------------------------------------------------------------------------*/
561
562 static int __devinit spidev_probe(struct spi_device *spi)
563 {
564         struct spidev_data      *spidev;
565         int                     status;
566         unsigned long           minor;
567
568         /* Allocate driver data */
569         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
570         if (!spidev)
571                 return -ENOMEM;
572
573         /* Initialize the driver data */
574         spidev->spi = spi;
575         spin_lock_init(&spidev->spi_lock);
576         mutex_init(&spidev->buf_lock);
577
578         INIT_LIST_HEAD(&spidev->device_entry);
579
580         /* If we can allocate a minor number, hook up this device.
581          * Reusing minors is fine so long as udev or mdev is working.
582          */
583         mutex_lock(&device_list_lock);
584         minor = find_first_zero_bit(minors, N_SPI_MINORS);
585         if (minor < N_SPI_MINORS) {
586                 struct device *dev;
587
588                 spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
589                 dev = device_create(spidev_class, &spi->dev, spidev->devt,
590                                     spidev, "spidev%d.%d",
591                                     spi->master->bus_num, spi->chip_select);
592                 status = IS_ERR(dev) ? PTR_ERR(dev) : 0;
593         } else {
594                 dev_dbg(&spi->dev, "no minor number available!\n");
595                 status = -ENODEV;
596         }
597         if (status == 0) {
598                 set_bit(minor, minors);
599                 list_add(&spidev->device_entry, &device_list);
600         }
601         mutex_unlock(&device_list_lock);
602
603         if (status == 0)
604                 spi_set_drvdata(spi, spidev);
605         else
606                 kfree(spidev);
607
608         return status;
609 }
610
611 static int __devexit spidev_remove(struct spi_device *spi)
612 {
613         struct spidev_data      *spidev = spi_get_drvdata(spi);
614
615         /* make sure ops on existing fds can abort cleanly */
616         spin_lock_irq(&spidev->spi_lock);
617         spidev->spi = NULL;
618         spi_set_drvdata(spi, NULL);
619         spin_unlock_irq(&spidev->spi_lock);
620
621         /* prevent new opens */
622         mutex_lock(&device_list_lock);
623         list_del(&spidev->device_entry);
624         device_destroy(spidev_class, spidev->devt);
625         clear_bit(MINOR(spidev->devt), minors);
626         if (spidev->users == 0)
627                 kfree(spidev);
628         mutex_unlock(&device_list_lock);
629
630         return 0;
631 }
632
633 static struct spi_driver spidev_spi_driver = {
634         .driver = {
635                 .name =         "spidev",
636                 .owner =        THIS_MODULE,
637         },
638         .probe =        spidev_probe,
639         .remove =       __devexit_p(spidev_remove),
640
641         /* NOTE:  suspend/resume methods are not necessary here.
642          * We don't do anything except pass the requests to/from
643          * the underlying controller.  The refrigerator handles
644          * most issues; the controller driver handles the rest.
645          */
646 };
647
648 /*-------------------------------------------------------------------------*/
649
650 static int __init spidev_init(void)
651 {
652         int status;
653
654         /* Claim our 256 reserved device numbers.  Then register a class
655          * that will key udev/mdev to add/remove /dev nodes.  Last, register
656          * the driver which manages those device numbers.
657          */
658         BUILD_BUG_ON(N_SPI_MINORS > 256);
659         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
660         if (status < 0)
661                 return status;
662
663         spidev_class = class_create(THIS_MODULE, "spidev");
664         if (IS_ERR(spidev_class)) {
665                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
666                 return PTR_ERR(spidev_class);
667         }
668
669         status = spi_register_driver(&spidev_spi_driver);
670         if (status < 0) {
671                 class_destroy(spidev_class);
672                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
673         }
674         return status;
675 }
676 module_init(spidev_init);
677
678 static void __exit spidev_exit(void)
679 {
680         spi_unregister_driver(&spidev_spi_driver);
681         class_destroy(spidev_class);
682         unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
683 }
684 module_exit(spidev_exit);
685
686 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
687 MODULE_DESCRIPTION("User mode SPI device interface");
688 MODULE_LICENSE("GPL");
689 MODULE_ALIAS("spi:spidev");