2 * Simple synchronous userspace interface to SPI devices
4 * Copyright (C) 2006 SWAPP
5 * Andrea Paterniani <a.paterniani@swapp-eng.it>
6 * Copyright (C) 2007 David Brownell (simplification, cleanup)
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.
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.
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.
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/ioctl.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 #include <linux/compat.h>
35 #include <linux/spi/spi.h>
36 #include <linux/spi/spidev.h>
38 #include <asm/uaccess.h>
42 * This supports access to SPI devices using normal userspace I/O calls.
43 * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
44 * and often mask message boundaries, full SPI support requires full duplex
45 * transfers. There are several kinds of internal message boundaries to
46 * handle chipselect management and other protocol options.
48 * SPI has a character major number assigned. We allocate minor numbers
49 * dynamically using a bitmask. You must use hotplug tools, such as udev
50 * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
51 * nodes, since there is no fixed association of minor numbers with any
52 * particular SPI bus or device.
54 #define SPIDEV_MAJOR 153 /* assigned */
55 #define N_SPI_MINORS 32 /* ... up to 256 */
57 static DECLARE_BITMAP(minors, N_SPI_MINORS);
60 /* Bit masks for spi_device.mode management. Note that incorrect
61 * settings for some settings can cause *lots* of trouble for other
62 * devices on a shared bus:
64 * - CS_HIGH ... this device will be active when it shouldn't be
65 * - 3WIRE ... when active, it won't behave as it should
66 * - NO_CS ... there will be no explicit message boundaries; this
67 * is completely incompatible with the shared bus model
68 * - READY ... transfers may proceed when they shouldn't.
70 * REVISIT should changing those flags be privileged?
72 #define SPI_MODE_MASK (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
73 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \
74 | SPI_NO_CS | SPI_READY)
79 struct spi_device *spi;
80 struct list_head device_entry;
82 /* buffer is NULL unless this device is open (users > 0) */
83 struct mutex buf_lock;
88 static LIST_HEAD(device_list);
89 static DEFINE_MUTEX(device_list_lock);
91 static unsigned bufsiz = 4096;
92 module_param(bufsiz, uint, S_IRUGO);
93 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
95 /*-------------------------------------------------------------------------*/
98 * We can't use the standard synchronous wrappers for file I/O; we
99 * need to protect against async removal of the underlying spi_device.
101 static void spidev_complete(void *arg)
107 spidev_sync(struct spidev_data *spidev, struct spi_message *message)
109 DECLARE_COMPLETION_ONSTACK(done);
112 message->complete = spidev_complete;
113 message->context = &done;
115 spin_lock_irq(&spidev->spi_lock);
116 if (spidev->spi == NULL)
119 status = spi_async(spidev->spi, message);
120 spin_unlock_irq(&spidev->spi_lock);
123 wait_for_completion(&done);
124 status = message->status;
126 status = message->actual_length;
131 static inline ssize_t
132 spidev_sync_write(struct spidev_data *spidev, size_t len)
134 struct spi_transfer t = {
135 .tx_buf = spidev->buffer,
138 struct spi_message m;
140 spi_message_init(&m);
141 spi_message_add_tail(&t, &m);
142 return spidev_sync(spidev, &m);
145 static inline ssize_t
146 spidev_sync_read(struct spidev_data *spidev, size_t len)
148 struct spi_transfer t = {
149 .rx_buf = spidev->buffer,
152 struct spi_message m;
154 spi_message_init(&m);
155 spi_message_add_tail(&t, &m);
156 return spidev_sync(spidev, &m);
159 /*-------------------------------------------------------------------------*/
161 /* Read-only message with current device setup */
163 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
165 struct spidev_data *spidev;
168 /* chipselect only toggles at start or end of operation */
172 spidev = filp->private_data;
174 mutex_lock(&spidev->buf_lock);
175 status = spidev_sync_read(spidev, count);
177 unsigned long missing;
179 missing = copy_to_user(buf, spidev->buffer, status);
180 if (missing == status)
183 status = status - missing;
185 mutex_unlock(&spidev->buf_lock);
190 /* Write-only message with current device setup */
192 spidev_write(struct file *filp, const char __user *buf,
193 size_t count, loff_t *f_pos)
195 struct spidev_data *spidev;
197 unsigned long missing;
199 /* chipselect only toggles at start or end of operation */
203 spidev = filp->private_data;
205 mutex_lock(&spidev->buf_lock);
206 missing = copy_from_user(spidev->buffer, buf, count);
208 status = spidev_sync_write(spidev, count);
211 mutex_unlock(&spidev->buf_lock);
216 static int spidev_message(struct spidev_data *spidev,
217 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
219 struct spi_message msg;
220 struct spi_transfer *k_xfers;
221 struct spi_transfer *k_tmp;
222 struct spi_ioc_transfer *u_tmp;
225 int status = -EFAULT;
227 spi_message_init(&msg);
228 k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
232 /* Construct spi_message, copying any tx data to bounce buffer.
233 * We walk the array of user-provided transfers, using each one
234 * to initialize a kernel version of the same transfer.
236 buf = spidev->buffer;
238 for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
240 n--, k_tmp++, u_tmp++) {
241 k_tmp->len = u_tmp->len;
244 /* Check total length of transfers. Also check each
245 * transfer length to avoid arithmetic overflow.
247 if (total > bufsiz || k_tmp->len > bufsiz) {
254 if (!access_ok(VERIFY_WRITE, (u8 __user *)
255 (uintptr_t) u_tmp->rx_buf,
261 if (copy_from_user(buf, (const u8 __user *)
262 (uintptr_t) u_tmp->tx_buf,
268 k_tmp->cs_change = !!u_tmp->cs_change;
269 k_tmp->bits_per_word = u_tmp->bits_per_word;
270 k_tmp->delay_usecs = u_tmp->delay_usecs;
271 k_tmp->speed_hz = u_tmp->speed_hz;
273 dev_dbg(&spidev->spi->dev,
274 " xfer len %zd %s%s%s%dbits %u usec %uHz\n",
276 u_tmp->rx_buf ? "rx " : "",
277 u_tmp->tx_buf ? "tx " : "",
278 u_tmp->cs_change ? "cs " : "",
279 u_tmp->bits_per_word ? : spidev->spi->bits_per_word,
281 u_tmp->speed_hz ? : spidev->spi->max_speed_hz);
283 spi_message_add_tail(k_tmp, &msg);
286 status = spidev_sync(spidev, &msg);
290 /* copy any rx data out of bounce buffer */
291 buf = spidev->buffer;
292 for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
294 if (__copy_to_user((u8 __user *)
295 (uintptr_t) u_tmp->rx_buf, buf,
311 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
315 struct spidev_data *spidev;
316 struct spi_device *spi;
319 struct spi_ioc_transfer *ioc;
321 /* Check type and command number */
322 if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
325 /* Check access direction once here; don't repeat below.
326 * IOC_DIR is from the user perspective, while access_ok is
327 * from the kernel perspective; so they look reversed.
329 if (_IOC_DIR(cmd) & _IOC_READ)
330 err = !access_ok(VERIFY_WRITE,
331 (void __user *)arg, _IOC_SIZE(cmd));
332 if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
333 err = !access_ok(VERIFY_READ,
334 (void __user *)arg, _IOC_SIZE(cmd));
338 /* guard against device removal before, or while,
339 * we issue this ioctl.
341 spidev = filp->private_data;
342 spin_lock_irq(&spidev->spi_lock);
343 spi = spi_dev_get(spidev->spi);
344 spin_unlock_irq(&spidev->spi_lock);
349 /* use the buffer lock here for triple duty:
350 * - prevent I/O (from us) so calling spi_setup() is safe;
351 * - prevent concurrent SPI_IOC_WR_* from morphing
352 * data fields while SPI_IOC_RD_* reads them;
353 * - SPI_IOC_MESSAGE needs the buffer locked "normally".
355 mutex_lock(&spidev->buf_lock);
359 case SPI_IOC_RD_MODE:
360 retval = __put_user(spi->mode & SPI_MODE_MASK,
363 case SPI_IOC_RD_LSB_FIRST:
364 retval = __put_user((spi->mode & SPI_LSB_FIRST) ? 1 : 0,
367 case SPI_IOC_RD_BITS_PER_WORD:
368 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
370 case SPI_IOC_RD_MAX_SPEED_HZ:
371 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg);
375 case SPI_IOC_WR_MODE:
376 retval = __get_user(tmp, (u8 __user *)arg);
380 if (tmp & ~SPI_MODE_MASK) {
385 tmp |= spi->mode & ~SPI_MODE_MASK;
387 retval = spi_setup(spi);
391 dev_dbg(&spi->dev, "spi mode %02x\n", tmp);
394 case SPI_IOC_WR_LSB_FIRST:
395 retval = __get_user(tmp, (__u8 __user *)arg);
400 spi->mode |= SPI_LSB_FIRST;
402 spi->mode &= ~SPI_LSB_FIRST;
403 retval = spi_setup(spi);
407 dev_dbg(&spi->dev, "%csb first\n",
411 case SPI_IOC_WR_BITS_PER_WORD:
412 retval = __get_user(tmp, (__u8 __user *)arg);
414 u8 save = spi->bits_per_word;
416 spi->bits_per_word = tmp;
417 retval = spi_setup(spi);
419 spi->bits_per_word = save;
421 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
424 case SPI_IOC_WR_MAX_SPEED_HZ:
425 retval = __get_user(tmp, (__u32 __user *)arg);
427 u32 save = spi->max_speed_hz;
429 spi->max_speed_hz = tmp;
430 retval = spi_setup(spi);
432 spi->max_speed_hz = save;
434 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
439 /* segmented and/or full-duplex I/O request */
440 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
441 || _IOC_DIR(cmd) != _IOC_WRITE) {
446 tmp = _IOC_SIZE(cmd);
447 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) {
451 n_ioc = tmp / sizeof(struct spi_ioc_transfer);
455 /* copy into scratch area */
456 ioc = kmalloc(tmp, GFP_KERNEL);
461 if (__copy_from_user(ioc, (void __user *)arg, tmp)) {
467 /* translate to spi_message, execute */
468 retval = spidev_message(spidev, ioc, n_ioc);
473 mutex_unlock(&spidev->buf_lock);
480 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
482 return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
485 #define spidev_compat_ioctl NULL
486 #endif /* CONFIG_COMPAT */
488 static int spidev_open(struct inode *inode, struct file *filp)
490 struct spidev_data *spidev;
493 mutex_lock(&device_list_lock);
495 list_for_each_entry(spidev, &device_list, device_entry) {
496 if (spidev->devt == inode->i_rdev) {
502 if (!spidev->buffer) {
503 spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
504 if (!spidev->buffer) {
505 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
511 filp->private_data = spidev;
512 nonseekable_open(inode, filp);
515 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
517 mutex_unlock(&device_list_lock);
521 static int spidev_release(struct inode *inode, struct file *filp)
523 struct spidev_data *spidev;
526 mutex_lock(&device_list_lock);
527 spidev = filp->private_data;
528 filp->private_data = NULL;
532 if (!spidev->users) {
535 kfree(spidev->buffer);
536 spidev->buffer = NULL;
538 /* ... after we unbound from the underlying device? */
539 spin_lock_irq(&spidev->spi_lock);
540 dofree = (spidev->spi == NULL);
541 spin_unlock_irq(&spidev->spi_lock);
546 mutex_unlock(&device_list_lock);
551 static const struct file_operations spidev_fops = {
552 .owner = THIS_MODULE,
553 /* REVISIT switch to aio primitives, so that userspace
554 * gets more complete API coverage. It'll simplify things
555 * too, except for the locking.
557 .write = spidev_write,
559 .unlocked_ioctl = spidev_ioctl,
560 .compat_ioctl = spidev_compat_ioctl,
562 .release = spidev_release,
566 /*-------------------------------------------------------------------------*/
568 /* The main reason to have this class is to make mdev/udev create the
569 * /dev/spidevB.C character device nodes exposing our userspace API.
570 * It also simplifies memory management.
573 static struct class *spidev_class;
575 /*-------------------------------------------------------------------------*/
577 static int __devinit spidev_probe(struct spi_device *spi)
579 struct spidev_data *spidev;
583 /* Allocate driver data */
584 spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
588 /* Initialize the driver data */
590 spin_lock_init(&spidev->spi_lock);
591 mutex_init(&spidev->buf_lock);
593 INIT_LIST_HEAD(&spidev->device_entry);
595 /* If we can allocate a minor number, hook up this device.
596 * Reusing minors is fine so long as udev or mdev is working.
598 mutex_lock(&device_list_lock);
599 minor = find_first_zero_bit(minors, N_SPI_MINORS);
600 if (minor < N_SPI_MINORS) {
603 spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
604 dev = device_create(spidev_class, &spi->dev, spidev->devt,
605 spidev, "spidev%d.%d",
606 spi->master->bus_num, spi->chip_select);
607 status = IS_ERR(dev) ? PTR_ERR(dev) : 0;
609 dev_dbg(&spi->dev, "no minor number available!\n");
613 set_bit(minor, minors);
614 list_add(&spidev->device_entry, &device_list);
616 mutex_unlock(&device_list_lock);
619 spi_set_drvdata(spi, spidev);
626 static int __devexit spidev_remove(struct spi_device *spi)
628 struct spidev_data *spidev = spi_get_drvdata(spi);
630 /* make sure ops on existing fds can abort cleanly */
631 spin_lock_irq(&spidev->spi_lock);
633 spi_set_drvdata(spi, NULL);
634 spin_unlock_irq(&spidev->spi_lock);
636 /* prevent new opens */
637 mutex_lock(&device_list_lock);
638 list_del(&spidev->device_entry);
639 device_destroy(spidev_class, spidev->devt);
640 clear_bit(MINOR(spidev->devt), minors);
641 if (spidev->users == 0)
643 mutex_unlock(&device_list_lock);
648 static struct spi_driver spidev_spi_driver = {
651 .owner = THIS_MODULE,
653 .probe = spidev_probe,
654 .remove = __devexit_p(spidev_remove),
656 /* NOTE: suspend/resume methods are not necessary here.
657 * We don't do anything except pass the requests to/from
658 * the underlying controller. The refrigerator handles
659 * most issues; the controller driver handles the rest.
663 /*-------------------------------------------------------------------------*/
665 static int __init spidev_init(void)
669 /* Claim our 256 reserved device numbers. Then register a class
670 * that will key udev/mdev to add/remove /dev nodes. Last, register
671 * the driver which manages those device numbers.
673 BUILD_BUG_ON(N_SPI_MINORS > 256);
674 status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
678 spidev_class = class_create(THIS_MODULE, "spidev");
679 if (IS_ERR(spidev_class)) {
680 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
681 return PTR_ERR(spidev_class);
684 status = spi_register_driver(&spidev_spi_driver);
686 class_destroy(spidev_class);
687 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
691 module_init(spidev_init);
693 static void __exit spidev_exit(void)
695 spi_unregister_driver(&spidev_spi_driver);
696 class_destroy(spidev_class);
697 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
699 module_exit(spidev_exit);
701 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
702 MODULE_DESCRIPTION("User mode SPI device interface");
703 MODULE_LICENSE("GPL");
704 MODULE_ALIAS("spi:spidev");