2 * spidev.c -- 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>
34 #include <linux/spi/spi.h>
35 #include <linux/spi/spidev.h>
37 #include <asm/uaccess.h>
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 of internal message boundaries to
45 * handle chipselect management and other protocol options.
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.
53 #define SPIDEV_MAJOR 153 /* assigned */
54 #define N_SPI_MINORS 32 /* ... up to 256 */
56 static unsigned long minors
[N_SPI_MINORS
/ BITS_PER_LONG
];
59 /* Bit masks for spi_device.mode management. Note that incorrect
60 * settings for CS_HIGH and 3WIRE can cause *lots* of trouble for other
61 * devices on a shared bus: CS_HIGH, because this device will be
62 * active when it shouldn't be; 3WIRE, because when active it won't
63 * behave as it should.
65 * REVISIT should changing those two modes be privileged?
67 #define SPI_MODE_MASK (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
68 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP)
73 struct spi_device
*spi
;
74 struct list_head device_entry
;
76 /* buffer is NULL unless this device is open (users > 0) */
77 struct mutex buf_lock
;
82 static LIST_HEAD(device_list
);
83 static DEFINE_MUTEX(device_list_lock
);
85 static unsigned bufsiz
= 4096;
86 module_param(bufsiz
, uint
, S_IRUGO
);
87 MODULE_PARM_DESC(bufsiz
, "data bytes in biggest supported SPI message");
89 /*-------------------------------------------------------------------------*/
92 * We can't use the standard synchronous wrappers for file I/O; we
93 * need to protect against async removal of the underlying spi_device.
95 static void spidev_complete(void *arg
)
101 spidev_sync(struct spidev_data
*spidev
, struct spi_message
*message
)
103 DECLARE_COMPLETION_ONSTACK(done
);
106 message
->complete
= spidev_complete
;
107 message
->context
= &done
;
109 spin_lock_irq(&spidev
->spi_lock
);
110 if (spidev
->spi
== NULL
)
113 status
= spi_async(spidev
->spi
, message
);
114 spin_unlock_irq(&spidev
->spi_lock
);
117 wait_for_completion(&done
);
118 status
= message
->status
;
120 status
= message
->actual_length
;
125 static inline ssize_t
126 spidev_sync_write(struct spidev_data
*spidev
, size_t len
)
128 struct spi_transfer t
= {
129 .tx_buf
= spidev
->buffer
,
132 struct spi_message m
;
134 spi_message_init(&m
);
135 spi_message_add_tail(&t
, &m
);
136 return spidev_sync(spidev
, &m
);
139 static inline ssize_t
140 spidev_sync_read(struct spidev_data
*spidev
, size_t len
)
142 struct spi_transfer t
= {
143 .rx_buf
= spidev
->buffer
,
146 struct spi_message m
;
148 spi_message_init(&m
);
149 spi_message_add_tail(&t
, &m
);
150 return spidev_sync(spidev
, &m
);
153 /*-------------------------------------------------------------------------*/
155 /* Read-only message with current device setup */
157 spidev_read(struct file
*filp
, char __user
*buf
, size_t count
, loff_t
*f_pos
)
159 struct spidev_data
*spidev
;
162 /* chipselect only toggles at start or end of operation */
166 spidev
= filp
->private_data
;
168 mutex_lock(&spidev
->buf_lock
);
169 status
= spidev_sync_read(spidev
, count
);
171 unsigned long missing
;
173 missing
= copy_to_user(buf
, spidev
->buffer
, status
);
174 if (missing
== status
)
177 status
= status
- missing
;
179 mutex_unlock(&spidev
->buf_lock
);
184 /* Write-only message with current device setup */
186 spidev_write(struct file
*filp
, const char __user
*buf
,
187 size_t count
, loff_t
*f_pos
)
189 struct spidev_data
*spidev
;
191 unsigned long missing
;
193 /* chipselect only toggles at start or end of operation */
197 spidev
= filp
->private_data
;
199 mutex_lock(&spidev
->buf_lock
);
200 missing
= copy_from_user(spidev
->buffer
, buf
, count
);
202 status
= spidev_sync_write(spidev
, count
);
205 mutex_unlock(&spidev
->buf_lock
);
210 static int spidev_message(struct spidev_data
*spidev
,
211 struct spi_ioc_transfer
*u_xfers
, unsigned n_xfers
)
213 struct spi_message msg
;
214 struct spi_transfer
*k_xfers
;
215 struct spi_transfer
*k_tmp
;
216 struct spi_ioc_transfer
*u_tmp
;
219 int status
= -EFAULT
;
221 spi_message_init(&msg
);
222 k_xfers
= kcalloc(n_xfers
, sizeof(*k_tmp
), GFP_KERNEL
);
226 /* Construct spi_message, copying any tx data to bounce buffer.
227 * We walk the array of user-provided transfers, using each one
228 * to initialize a kernel version of the same transfer.
230 mutex_lock(&spidev
->buf_lock
);
231 buf
= spidev
->buffer
;
233 for (n
= n_xfers
, k_tmp
= k_xfers
, u_tmp
= u_xfers
;
235 n
--, k_tmp
++, u_tmp
++) {
236 k_tmp
->len
= u_tmp
->len
;
239 if (total
> bufsiz
) {
246 if (!access_ok(VERIFY_WRITE
, (u8 __user
*)
247 (uintptr_t) u_tmp
->rx_buf
,
253 if (copy_from_user(buf
, (const u8 __user
*)
254 (uintptr_t) u_tmp
->tx_buf
,
260 k_tmp
->cs_change
= !!u_tmp
->cs_change
;
261 k_tmp
->bits_per_word
= u_tmp
->bits_per_word
;
262 k_tmp
->delay_usecs
= u_tmp
->delay_usecs
;
263 k_tmp
->speed_hz
= u_tmp
->speed_hz
;
266 " xfer len %zd %s%s%s%dbits %u usec %uHz\n",
268 u_tmp
->rx_buf
? "rx " : "",
269 u_tmp
->tx_buf
? "tx " : "",
270 u_tmp
->cs_change
? "cs " : "",
271 u_tmp
->bits_per_word
? : spi
->bits_per_word
,
273 u_tmp
->speed_hz
? : spi
->max_speed_hz
);
275 spi_message_add_tail(k_tmp
, &msg
);
278 status
= spidev_sync(spidev
, &msg
);
282 /* copy any rx data out of bounce buffer */
283 buf
= spidev
->buffer
;
284 for (n
= n_xfers
, u_tmp
= u_xfers
; n
; n
--, u_tmp
++) {
286 if (__copy_to_user((u8 __user
*)
287 (uintptr_t) u_tmp
->rx_buf
, buf
,
298 mutex_unlock(&spidev
->buf_lock
);
304 spidev_ioctl(struct inode
*inode
, struct file
*filp
,
305 unsigned int cmd
, unsigned long arg
)
309 struct spidev_data
*spidev
;
310 struct spi_device
*spi
;
313 struct spi_ioc_transfer
*ioc
;
315 /* Check type and command number */
316 if (_IOC_TYPE(cmd
) != SPI_IOC_MAGIC
)
319 /* Check access direction once here; don't repeat below.
320 * IOC_DIR is from the user perspective, while access_ok is
321 * from the kernel perspective; so they look reversed.
323 if (_IOC_DIR(cmd
) & _IOC_READ
)
324 err
= !access_ok(VERIFY_WRITE
,
325 (void __user
*)arg
, _IOC_SIZE(cmd
));
326 if (err
== 0 && _IOC_DIR(cmd
) & _IOC_WRITE
)
327 err
= !access_ok(VERIFY_READ
,
328 (void __user
*)arg
, _IOC_SIZE(cmd
));
332 /* guard against device removal before, or while,
333 * we issue this ioctl.
335 spidev
= filp
->private_data
;
336 spin_lock_irq(&spidev
->spi_lock
);
337 spi
= spi_dev_get(spidev
->spi
);
338 spin_unlock_irq(&spidev
->spi_lock
);
345 case SPI_IOC_RD_MODE
:
346 retval
= __put_user(spi
->mode
& SPI_MODE_MASK
,
349 case SPI_IOC_RD_LSB_FIRST
:
350 retval
= __put_user((spi
->mode
& SPI_LSB_FIRST
) ? 1 : 0,
353 case SPI_IOC_RD_BITS_PER_WORD
:
354 retval
= __put_user(spi
->bits_per_word
, (__u8 __user
*)arg
);
356 case SPI_IOC_RD_MAX_SPEED_HZ
:
357 retval
= __put_user(spi
->max_speed_hz
, (__u32 __user
*)arg
);
361 case SPI_IOC_WR_MODE
:
362 retval
= __get_user(tmp
, (u8 __user
*)arg
);
366 if (tmp
& ~SPI_MODE_MASK
) {
371 tmp
|= spi
->mode
& ~SPI_MODE_MASK
;
373 retval
= spi_setup(spi
);
377 dev_dbg(&spi
->dev
, "spi mode %02x\n", tmp
);
380 case SPI_IOC_WR_LSB_FIRST
:
381 retval
= __get_user(tmp
, (__u8 __user
*)arg
);
386 spi
->mode
|= SPI_LSB_FIRST
;
388 spi
->mode
&= ~SPI_LSB_FIRST
;
389 retval
= spi_setup(spi
);
393 dev_dbg(&spi
->dev
, "%csb first\n",
397 case SPI_IOC_WR_BITS_PER_WORD
:
398 retval
= __get_user(tmp
, (__u8 __user
*)arg
);
400 u8 save
= spi
->bits_per_word
;
402 spi
->bits_per_word
= tmp
;
403 retval
= spi_setup(spi
);
405 spi
->bits_per_word
= save
;
407 dev_dbg(&spi
->dev
, "%d bits per word\n", tmp
);
410 case SPI_IOC_WR_MAX_SPEED_HZ
:
411 retval
= __get_user(tmp
, (__u32 __user
*)arg
);
413 u32 save
= spi
->max_speed_hz
;
415 spi
->max_speed_hz
= tmp
;
416 retval
= spi_setup(spi
);
418 spi
->max_speed_hz
= save
;
420 dev_dbg(&spi
->dev
, "%d Hz (max)\n", tmp
);
425 /* segmented and/or full-duplex I/O request */
426 if (_IOC_NR(cmd
) != _IOC_NR(SPI_IOC_MESSAGE(0))
427 || _IOC_DIR(cmd
) != _IOC_WRITE
) {
432 tmp
= _IOC_SIZE(cmd
);
433 if ((tmp
% sizeof(struct spi_ioc_transfer
)) != 0) {
437 n_ioc
= tmp
/ sizeof(struct spi_ioc_transfer
);
441 /* copy into scratch area */
442 ioc
= kmalloc(tmp
, GFP_KERNEL
);
447 if (__copy_from_user(ioc
, (void __user
*)arg
, tmp
)) {
453 /* translate to spi_message, execute */
454 retval
= spidev_message(spidev
, ioc
, n_ioc
);
462 static int spidev_open(struct inode
*inode
, struct file
*filp
)
464 struct spidev_data
*spidev
;
467 mutex_lock(&device_list_lock
);
469 list_for_each_entry(spidev
, &device_list
, device_entry
) {
470 if (spidev
->devt
== inode
->i_rdev
) {
476 if (!spidev
->buffer
) {
477 spidev
->buffer
= kmalloc(bufsiz
, GFP_KERNEL
);
478 if (!spidev
->buffer
) {
479 dev_dbg(&spidev
->spi
->dev
, "open/ENOMEM\n");
485 filp
->private_data
= spidev
;
486 nonseekable_open(inode
, filp
);
489 pr_debug("spidev: nothing for minor %d\n", iminor(inode
));
491 mutex_unlock(&device_list_lock
);
495 static int spidev_release(struct inode
*inode
, struct file
*filp
)
497 struct spidev_data
*spidev
;
500 mutex_lock(&device_list_lock
);
501 spidev
= filp
->private_data
;
502 filp
->private_data
= NULL
;
506 if (!spidev
->users
) {
509 kfree(spidev
->buffer
);
510 spidev
->buffer
= NULL
;
512 /* ... after we unbound from the underlying device? */
513 spin_lock_irq(&spidev
->spi_lock
);
514 dofree
= (spidev
->spi
== NULL
);
515 spin_unlock_irq(&spidev
->spi_lock
);
520 mutex_unlock(&device_list_lock
);
525 static struct file_operations spidev_fops
= {
526 .owner
= THIS_MODULE
,
527 /* REVISIT switch to aio primitives, so that userspace
528 * gets more complete API coverage. It'll simplify things
529 * too, except for the locking.
531 .write
= spidev_write
,
533 .ioctl
= spidev_ioctl
,
535 .release
= spidev_release
,
538 /*-------------------------------------------------------------------------*/
540 /* The main reason to have this class is to make mdev/udev create the
541 * /dev/spidevB.C character device nodes exposing our userspace API.
542 * It also simplifies memory management.
545 static struct class *spidev_class
;
547 /*-------------------------------------------------------------------------*/
549 static int spidev_probe(struct spi_device
*spi
)
551 struct spidev_data
*spidev
;
555 /* Allocate driver data */
556 spidev
= kzalloc(sizeof(*spidev
), GFP_KERNEL
);
560 /* Initialize the driver data */
562 spin_lock_init(&spidev
->spi_lock
);
563 mutex_init(&spidev
->buf_lock
);
565 INIT_LIST_HEAD(&spidev
->device_entry
);
567 /* If we can allocate a minor number, hook up this device.
568 * Reusing minors is fine so long as udev or mdev is working.
570 mutex_lock(&device_list_lock
);
571 minor
= find_first_zero_bit(minors
, N_SPI_MINORS
);
572 if (minor
< N_SPI_MINORS
) {
575 spidev
->devt
= MKDEV(SPIDEV_MAJOR
, minor
);
576 dev
= device_create(spidev_class
, &spi
->dev
, spidev
->devt
,
578 spi
->master
->bus_num
, spi
->chip_select
);
579 status
= IS_ERR(dev
) ? PTR_ERR(dev
) : 0;
581 dev_dbg(&spi
->dev
, "no minor number available!\n");
585 set_bit(minor
, minors
);
586 spi_set_drvdata(spi
, spidev
);
587 list_add(&spidev
->device_entry
, &device_list
);
589 mutex_unlock(&device_list_lock
);
597 static int spidev_remove(struct spi_device
*spi
)
599 struct spidev_data
*spidev
= spi_get_drvdata(spi
);
601 /* make sure ops on existing fds can abort cleanly */
602 spin_lock_irq(&spidev
->spi_lock
);
604 spi_set_drvdata(spi
, NULL
);
605 spin_unlock_irq(&spidev
->spi_lock
);
607 /* prevent new opens */
608 mutex_lock(&device_list_lock
);
609 list_del(&spidev
->device_entry
);
610 device_destroy(spidev_class
, spidev
->devt
);
611 clear_bit(MINOR(spidev
->devt
), minors
);
612 if (spidev
->users
== 0)
614 mutex_unlock(&device_list_lock
);
619 static struct spi_driver spidev_spi
= {
622 .owner
= THIS_MODULE
,
624 .probe
= spidev_probe
,
625 .remove
= __devexit_p(spidev_remove
),
627 /* NOTE: suspend/resume methods are not necessary here.
628 * We don't do anything except pass the requests to/from
629 * the underlying controller. The refrigerator handles
630 * most issues; the controller driver handles the rest.
634 /*-------------------------------------------------------------------------*/
636 static int __init
spidev_init(void)
640 /* Claim our 256 reserved device numbers. Then register a class
641 * that will key udev/mdev to add/remove /dev nodes. Last, register
642 * the driver which manages those device numbers.
644 BUILD_BUG_ON(N_SPI_MINORS
> 256);
645 status
= register_chrdev(SPIDEV_MAJOR
, "spi", &spidev_fops
);
649 spidev_class
= class_create(THIS_MODULE
, "spidev");
650 if (IS_ERR(spidev_class
)) {
651 unregister_chrdev(SPIDEV_MAJOR
, spidev_spi
.driver
.name
);
652 return PTR_ERR(spidev_class
);
655 status
= spi_register_driver(&spidev_spi
);
657 class_destroy(spidev_class
);
658 unregister_chrdev(SPIDEV_MAJOR
, spidev_spi
.driver
.name
);
662 module_init(spidev_init
);
664 static void __exit
spidev_exit(void)
666 spi_unregister_driver(&spidev_spi
);
667 class_destroy(spidev_class
);
668 unregister_chrdev(SPIDEV_MAJOR
, spidev_spi
.driver
.name
);
670 module_exit(spidev_exit
);
672 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
673 MODULE_DESCRIPTION("User mode SPI device interface");
674 MODULE_LICENSE("GPL");