xref: /openbmc/linux/drivers/spi/spidev.c (revision 0ad53fe3)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Simple synchronous userspace interface to SPI devices
4  *
5  * Copyright (C) 2006 SWAPP
6  *	Andrea Paterniani <a.paterniani@swapp-eng.it>
7  * Copyright (C) 2007 David Brownell (simplification, cleanup)
8  */
9 
10 #include <linux/init.h>
11 #include <linux/module.h>
12 #include <linux/ioctl.h>
13 #include <linux/fs.h>
14 #include <linux/device.h>
15 #include <linux/err.h>
16 #include <linux/list.h>
17 #include <linux/errno.h>
18 #include <linux/mutex.h>
19 #include <linux/slab.h>
20 #include <linux/compat.h>
21 #include <linux/of.h>
22 #include <linux/of_device.h>
23 #include <linux/acpi.h>
24 
25 #include <linux/spi/spi.h>
26 #include <linux/spi/spidev.h>
27 
28 #include <linux/uaccess.h>
29 
30 
31 /*
32  * This supports access to SPI devices using normal userspace I/O calls.
33  * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
34  * and often mask message boundaries, full SPI support requires full duplex
35  * transfers.  There are several kinds of internal message boundaries to
36  * handle chipselect management and other protocol options.
37  *
38  * SPI has a character major number assigned.  We allocate minor numbers
39  * dynamically using a bitmask.  You must use hotplug tools, such as udev
40  * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
41  * nodes, since there is no fixed association of minor numbers with any
42  * particular SPI bus or device.
43  */
44 #define SPIDEV_MAJOR			153	/* assigned */
45 #define N_SPI_MINORS			32	/* ... up to 256 */
46 
47 static DECLARE_BITMAP(minors, N_SPI_MINORS);
48 
49 
50 /* Bit masks for spi_device.mode management.  Note that incorrect
51  * settings for some settings can cause *lots* of trouble for other
52  * devices on a shared bus:
53  *
54  *  - CS_HIGH ... this device will be active when it shouldn't be
55  *  - 3WIRE ... when active, it won't behave as it should
56  *  - NO_CS ... there will be no explicit message boundaries; this
57  *	is completely incompatible with the shared bus model
58  *  - READY ... transfers may proceed when they shouldn't.
59  *
60  * REVISIT should changing those flags be privileged?
61  */
62 #define SPI_MODE_MASK		(SPI_MODE_X_MASK | SPI_CS_HIGH \
63 				| SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \
64 				| SPI_NO_CS | SPI_READY | SPI_TX_DUAL \
65 				| SPI_TX_QUAD | SPI_TX_OCTAL | SPI_RX_DUAL \
66 				| SPI_RX_QUAD | SPI_RX_OCTAL)
67 
68 struct spidev_data {
69 	dev_t			devt;
70 	spinlock_t		spi_lock;
71 	struct spi_device	*spi;
72 	struct list_head	device_entry;
73 
74 	/* TX/RX buffers are NULL unless this device is open (users > 0) */
75 	struct mutex		buf_lock;
76 	unsigned		users;
77 	u8			*tx_buffer;
78 	u8			*rx_buffer;
79 	u32			speed_hz;
80 };
81 
82 static LIST_HEAD(device_list);
83 static DEFINE_MUTEX(device_list_lock);
84 
85 static unsigned bufsiz = 4096;
86 module_param(bufsiz, uint, S_IRUGO);
87 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
88 
89 /*-------------------------------------------------------------------------*/
90 
91 static ssize_t
92 spidev_sync(struct spidev_data *spidev, struct spi_message *message)
93 {
94 	int status;
95 	struct spi_device *spi;
96 
97 	spin_lock_irq(&spidev->spi_lock);
98 	spi = spidev->spi;
99 	spin_unlock_irq(&spidev->spi_lock);
100 
101 	if (spi == NULL)
102 		status = -ESHUTDOWN;
103 	else
104 		status = spi_sync(spi, message);
105 
106 	if (status == 0)
107 		status = message->actual_length;
108 
109 	return status;
110 }
111 
112 static inline ssize_t
113 spidev_sync_write(struct spidev_data *spidev, size_t len)
114 {
115 	struct spi_transfer	t = {
116 			.tx_buf		= spidev->tx_buffer,
117 			.len		= len,
118 			.speed_hz	= spidev->speed_hz,
119 		};
120 	struct spi_message	m;
121 
122 	spi_message_init(&m);
123 	spi_message_add_tail(&t, &m);
124 	return spidev_sync(spidev, &m);
125 }
126 
127 static inline ssize_t
128 spidev_sync_read(struct spidev_data *spidev, size_t len)
129 {
130 	struct spi_transfer	t = {
131 			.rx_buf		= spidev->rx_buffer,
132 			.len		= len,
133 			.speed_hz	= spidev->speed_hz,
134 		};
135 	struct spi_message	m;
136 
137 	spi_message_init(&m);
138 	spi_message_add_tail(&t, &m);
139 	return spidev_sync(spidev, &m);
140 }
141 
142 /*-------------------------------------------------------------------------*/
143 
144 /* Read-only message with current device setup */
145 static ssize_t
146 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
147 {
148 	struct spidev_data	*spidev;
149 	ssize_t			status;
150 
151 	/* chipselect only toggles at start or end of operation */
152 	if (count > bufsiz)
153 		return -EMSGSIZE;
154 
155 	spidev = filp->private_data;
156 
157 	mutex_lock(&spidev->buf_lock);
158 	status = spidev_sync_read(spidev, count);
159 	if (status > 0) {
160 		unsigned long	missing;
161 
162 		missing = copy_to_user(buf, spidev->rx_buffer, status);
163 		if (missing == status)
164 			status = -EFAULT;
165 		else
166 			status = status - missing;
167 	}
168 	mutex_unlock(&spidev->buf_lock);
169 
170 	return status;
171 }
172 
173 /* Write-only message with current device setup */
174 static ssize_t
175 spidev_write(struct file *filp, const char __user *buf,
176 		size_t count, loff_t *f_pos)
177 {
178 	struct spidev_data	*spidev;
179 	ssize_t			status;
180 	unsigned long		missing;
181 
182 	/* chipselect only toggles at start or end of operation */
183 	if (count > bufsiz)
184 		return -EMSGSIZE;
185 
186 	spidev = filp->private_data;
187 
188 	mutex_lock(&spidev->buf_lock);
189 	missing = copy_from_user(spidev->tx_buffer, buf, count);
190 	if (missing == 0)
191 		status = spidev_sync_write(spidev, count);
192 	else
193 		status = -EFAULT;
194 	mutex_unlock(&spidev->buf_lock);
195 
196 	return status;
197 }
198 
199 static int spidev_message(struct spidev_data *spidev,
200 		struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
201 {
202 	struct spi_message	msg;
203 	struct spi_transfer	*k_xfers;
204 	struct spi_transfer	*k_tmp;
205 	struct spi_ioc_transfer *u_tmp;
206 	unsigned		n, total, tx_total, rx_total;
207 	u8			*tx_buf, *rx_buf;
208 	int			status = -EFAULT;
209 
210 	spi_message_init(&msg);
211 	k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
212 	if (k_xfers == NULL)
213 		return -ENOMEM;
214 
215 	/* Construct spi_message, copying any tx data to bounce buffer.
216 	 * We walk the array of user-provided transfers, using each one
217 	 * to initialize a kernel version of the same transfer.
218 	 */
219 	tx_buf = spidev->tx_buffer;
220 	rx_buf = spidev->rx_buffer;
221 	total = 0;
222 	tx_total = 0;
223 	rx_total = 0;
224 	for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
225 			n;
226 			n--, k_tmp++, u_tmp++) {
227 		/* Ensure that also following allocations from rx_buf/tx_buf will meet
228 		 * DMA alignment requirements.
229 		 */
230 		unsigned int len_aligned = ALIGN(u_tmp->len, ARCH_KMALLOC_MINALIGN);
231 
232 		k_tmp->len = u_tmp->len;
233 
234 		total += k_tmp->len;
235 		/* Since the function returns the total length of transfers
236 		 * on success, restrict the total to positive int values to
237 		 * avoid the return value looking like an error.  Also check
238 		 * each transfer length to avoid arithmetic overflow.
239 		 */
240 		if (total > INT_MAX || k_tmp->len > INT_MAX) {
241 			status = -EMSGSIZE;
242 			goto done;
243 		}
244 
245 		if (u_tmp->rx_buf) {
246 			/* this transfer needs space in RX bounce buffer */
247 			rx_total += len_aligned;
248 			if (rx_total > bufsiz) {
249 				status = -EMSGSIZE;
250 				goto done;
251 			}
252 			k_tmp->rx_buf = rx_buf;
253 			rx_buf += len_aligned;
254 		}
255 		if (u_tmp->tx_buf) {
256 			/* this transfer needs space in TX bounce buffer */
257 			tx_total += len_aligned;
258 			if (tx_total > bufsiz) {
259 				status = -EMSGSIZE;
260 				goto done;
261 			}
262 			k_tmp->tx_buf = tx_buf;
263 			if (copy_from_user(tx_buf, (const u8 __user *)
264 						(uintptr_t) u_tmp->tx_buf,
265 					u_tmp->len))
266 				goto done;
267 			tx_buf += len_aligned;
268 		}
269 
270 		k_tmp->cs_change = !!u_tmp->cs_change;
271 		k_tmp->tx_nbits = u_tmp->tx_nbits;
272 		k_tmp->rx_nbits = u_tmp->rx_nbits;
273 		k_tmp->bits_per_word = u_tmp->bits_per_word;
274 		k_tmp->delay.value = u_tmp->delay_usecs;
275 		k_tmp->delay.unit = SPI_DELAY_UNIT_USECS;
276 		k_tmp->speed_hz = u_tmp->speed_hz;
277 		k_tmp->word_delay.value = u_tmp->word_delay_usecs;
278 		k_tmp->word_delay.unit = SPI_DELAY_UNIT_USECS;
279 		if (!k_tmp->speed_hz)
280 			k_tmp->speed_hz = spidev->speed_hz;
281 #ifdef VERBOSE
282 		dev_dbg(&spidev->spi->dev,
283 			"  xfer len %u %s%s%s%dbits %u usec %u usec %uHz\n",
284 			k_tmp->len,
285 			k_tmp->rx_buf ? "rx " : "",
286 			k_tmp->tx_buf ? "tx " : "",
287 			k_tmp->cs_change ? "cs " : "",
288 			k_tmp->bits_per_word ? : spidev->spi->bits_per_word,
289 			k_tmp->delay.value,
290 			k_tmp->word_delay.value,
291 			k_tmp->speed_hz ? : spidev->spi->max_speed_hz);
292 #endif
293 		spi_message_add_tail(k_tmp, &msg);
294 	}
295 
296 	status = spidev_sync(spidev, &msg);
297 	if (status < 0)
298 		goto done;
299 
300 	/* copy any rx data out of bounce buffer */
301 	for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
302 			n;
303 			n--, k_tmp++, u_tmp++) {
304 		if (u_tmp->rx_buf) {
305 			if (copy_to_user((u8 __user *)
306 					(uintptr_t) u_tmp->rx_buf, k_tmp->rx_buf,
307 					u_tmp->len)) {
308 				status = -EFAULT;
309 				goto done;
310 			}
311 		}
312 	}
313 	status = total;
314 
315 done:
316 	kfree(k_xfers);
317 	return status;
318 }
319 
320 static struct spi_ioc_transfer *
321 spidev_get_ioc_message(unsigned int cmd, struct spi_ioc_transfer __user *u_ioc,
322 		unsigned *n_ioc)
323 {
324 	u32	tmp;
325 
326 	/* Check type, command number and direction */
327 	if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC
328 			|| _IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
329 			|| _IOC_DIR(cmd) != _IOC_WRITE)
330 		return ERR_PTR(-ENOTTY);
331 
332 	tmp = _IOC_SIZE(cmd);
333 	if ((tmp % sizeof(struct spi_ioc_transfer)) != 0)
334 		return ERR_PTR(-EINVAL);
335 	*n_ioc = tmp / sizeof(struct spi_ioc_transfer);
336 	if (*n_ioc == 0)
337 		return NULL;
338 
339 	/* copy into scratch area */
340 	return memdup_user(u_ioc, tmp);
341 }
342 
343 static long
344 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
345 {
346 	int			retval = 0;
347 	struct spidev_data	*spidev;
348 	struct spi_device	*spi;
349 	u32			tmp;
350 	unsigned		n_ioc;
351 	struct spi_ioc_transfer	*ioc;
352 
353 	/* Check type and command number */
354 	if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
355 		return -ENOTTY;
356 
357 	/* guard against device removal before, or while,
358 	 * we issue this ioctl.
359 	 */
360 	spidev = filp->private_data;
361 	spin_lock_irq(&spidev->spi_lock);
362 	spi = spi_dev_get(spidev->spi);
363 	spin_unlock_irq(&spidev->spi_lock);
364 
365 	if (spi == NULL)
366 		return -ESHUTDOWN;
367 
368 	/* use the buffer lock here for triple duty:
369 	 *  - prevent I/O (from us) so calling spi_setup() is safe;
370 	 *  - prevent concurrent SPI_IOC_WR_* from morphing
371 	 *    data fields while SPI_IOC_RD_* reads them;
372 	 *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
373 	 */
374 	mutex_lock(&spidev->buf_lock);
375 
376 	switch (cmd) {
377 	/* read requests */
378 	case SPI_IOC_RD_MODE:
379 		retval = put_user(spi->mode & SPI_MODE_MASK,
380 					(__u8 __user *)arg);
381 		break;
382 	case SPI_IOC_RD_MODE32:
383 		retval = put_user(spi->mode & SPI_MODE_MASK,
384 					(__u32 __user *)arg);
385 		break;
386 	case SPI_IOC_RD_LSB_FIRST:
387 		retval = put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
388 					(__u8 __user *)arg);
389 		break;
390 	case SPI_IOC_RD_BITS_PER_WORD:
391 		retval = put_user(spi->bits_per_word, (__u8 __user *)arg);
392 		break;
393 	case SPI_IOC_RD_MAX_SPEED_HZ:
394 		retval = put_user(spidev->speed_hz, (__u32 __user *)arg);
395 		break;
396 
397 	/* write requests */
398 	case SPI_IOC_WR_MODE:
399 	case SPI_IOC_WR_MODE32:
400 		if (cmd == SPI_IOC_WR_MODE)
401 			retval = get_user(tmp, (u8 __user *)arg);
402 		else
403 			retval = get_user(tmp, (u32 __user *)arg);
404 		if (retval == 0) {
405 			struct spi_controller *ctlr = spi->controller;
406 			u32	save = spi->mode;
407 
408 			if (tmp & ~SPI_MODE_MASK) {
409 				retval = -EINVAL;
410 				break;
411 			}
412 
413 			if (ctlr->use_gpio_descriptors && ctlr->cs_gpiods &&
414 			    ctlr->cs_gpiods[spi->chip_select])
415 				tmp |= SPI_CS_HIGH;
416 
417 			tmp |= spi->mode & ~SPI_MODE_MASK;
418 			spi->mode = (u16)tmp;
419 			retval = spi_setup(spi);
420 			if (retval < 0)
421 				spi->mode = save;
422 			else
423 				dev_dbg(&spi->dev, "spi mode %x\n", tmp);
424 		}
425 		break;
426 	case SPI_IOC_WR_LSB_FIRST:
427 		retval = get_user(tmp, (__u8 __user *)arg);
428 		if (retval == 0) {
429 			u32	save = spi->mode;
430 
431 			if (tmp)
432 				spi->mode |= SPI_LSB_FIRST;
433 			else
434 				spi->mode &= ~SPI_LSB_FIRST;
435 			retval = spi_setup(spi);
436 			if (retval < 0)
437 				spi->mode = save;
438 			else
439 				dev_dbg(&spi->dev, "%csb first\n",
440 						tmp ? 'l' : 'm');
441 		}
442 		break;
443 	case SPI_IOC_WR_BITS_PER_WORD:
444 		retval = get_user(tmp, (__u8 __user *)arg);
445 		if (retval == 0) {
446 			u8	save = spi->bits_per_word;
447 
448 			spi->bits_per_word = tmp;
449 			retval = spi_setup(spi);
450 			if (retval < 0)
451 				spi->bits_per_word = save;
452 			else
453 				dev_dbg(&spi->dev, "%d bits per word\n", tmp);
454 		}
455 		break;
456 	case SPI_IOC_WR_MAX_SPEED_HZ:
457 		retval = get_user(tmp, (__u32 __user *)arg);
458 		if (retval == 0) {
459 			u32	save = spi->max_speed_hz;
460 
461 			spi->max_speed_hz = tmp;
462 			retval = spi_setup(spi);
463 			if (retval == 0) {
464 				spidev->speed_hz = tmp;
465 				dev_dbg(&spi->dev, "%d Hz (max)\n",
466 					spidev->speed_hz);
467 			}
468 			spi->max_speed_hz = save;
469 		}
470 		break;
471 
472 	default:
473 		/* segmented and/or full-duplex I/O request */
474 		/* Check message and copy into scratch area */
475 		ioc = spidev_get_ioc_message(cmd,
476 				(struct spi_ioc_transfer __user *)arg, &n_ioc);
477 		if (IS_ERR(ioc)) {
478 			retval = PTR_ERR(ioc);
479 			break;
480 		}
481 		if (!ioc)
482 			break;	/* n_ioc is also 0 */
483 
484 		/* translate to spi_message, execute */
485 		retval = spidev_message(spidev, ioc, n_ioc);
486 		kfree(ioc);
487 		break;
488 	}
489 
490 	mutex_unlock(&spidev->buf_lock);
491 	spi_dev_put(spi);
492 	return retval;
493 }
494 
495 #ifdef CONFIG_COMPAT
496 static long
497 spidev_compat_ioc_message(struct file *filp, unsigned int cmd,
498 		unsigned long arg)
499 {
500 	struct spi_ioc_transfer __user	*u_ioc;
501 	int				retval = 0;
502 	struct spidev_data		*spidev;
503 	struct spi_device		*spi;
504 	unsigned			n_ioc, n;
505 	struct spi_ioc_transfer		*ioc;
506 
507 	u_ioc = (struct spi_ioc_transfer __user *) compat_ptr(arg);
508 
509 	/* guard against device removal before, or while,
510 	 * we issue this ioctl.
511 	 */
512 	spidev = filp->private_data;
513 	spin_lock_irq(&spidev->spi_lock);
514 	spi = spi_dev_get(spidev->spi);
515 	spin_unlock_irq(&spidev->spi_lock);
516 
517 	if (spi == NULL)
518 		return -ESHUTDOWN;
519 
520 	/* SPI_IOC_MESSAGE needs the buffer locked "normally" */
521 	mutex_lock(&spidev->buf_lock);
522 
523 	/* Check message and copy into scratch area */
524 	ioc = spidev_get_ioc_message(cmd, u_ioc, &n_ioc);
525 	if (IS_ERR(ioc)) {
526 		retval = PTR_ERR(ioc);
527 		goto done;
528 	}
529 	if (!ioc)
530 		goto done;	/* n_ioc is also 0 */
531 
532 	/* Convert buffer pointers */
533 	for (n = 0; n < n_ioc; n++) {
534 		ioc[n].rx_buf = (uintptr_t) compat_ptr(ioc[n].rx_buf);
535 		ioc[n].tx_buf = (uintptr_t) compat_ptr(ioc[n].tx_buf);
536 	}
537 
538 	/* translate to spi_message, execute */
539 	retval = spidev_message(spidev, ioc, n_ioc);
540 	kfree(ioc);
541 
542 done:
543 	mutex_unlock(&spidev->buf_lock);
544 	spi_dev_put(spi);
545 	return retval;
546 }
547 
548 static long
549 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
550 {
551 	if (_IOC_TYPE(cmd) == SPI_IOC_MAGIC
552 			&& _IOC_NR(cmd) == _IOC_NR(SPI_IOC_MESSAGE(0))
553 			&& _IOC_DIR(cmd) == _IOC_WRITE)
554 		return spidev_compat_ioc_message(filp, cmd, arg);
555 
556 	return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
557 }
558 #else
559 #define spidev_compat_ioctl NULL
560 #endif /* CONFIG_COMPAT */
561 
562 static int spidev_open(struct inode *inode, struct file *filp)
563 {
564 	struct spidev_data	*spidev;
565 	int			status = -ENXIO;
566 
567 	mutex_lock(&device_list_lock);
568 
569 	list_for_each_entry(spidev, &device_list, device_entry) {
570 		if (spidev->devt == inode->i_rdev) {
571 			status = 0;
572 			break;
573 		}
574 	}
575 
576 	if (status) {
577 		pr_debug("spidev: nothing for minor %d\n", iminor(inode));
578 		goto err_find_dev;
579 	}
580 
581 	if (!spidev->tx_buffer) {
582 		spidev->tx_buffer = kmalloc(bufsiz, GFP_KERNEL);
583 		if (!spidev->tx_buffer) {
584 			dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
585 			status = -ENOMEM;
586 			goto err_find_dev;
587 		}
588 	}
589 
590 	if (!spidev->rx_buffer) {
591 		spidev->rx_buffer = kmalloc(bufsiz, GFP_KERNEL);
592 		if (!spidev->rx_buffer) {
593 			dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
594 			status = -ENOMEM;
595 			goto err_alloc_rx_buf;
596 		}
597 	}
598 
599 	spidev->users++;
600 	filp->private_data = spidev;
601 	stream_open(inode, filp);
602 
603 	mutex_unlock(&device_list_lock);
604 	return 0;
605 
606 err_alloc_rx_buf:
607 	kfree(spidev->tx_buffer);
608 	spidev->tx_buffer = NULL;
609 err_find_dev:
610 	mutex_unlock(&device_list_lock);
611 	return status;
612 }
613 
614 static int spidev_release(struct inode *inode, struct file *filp)
615 {
616 	struct spidev_data	*spidev;
617 	int			dofree;
618 
619 	mutex_lock(&device_list_lock);
620 	spidev = filp->private_data;
621 	filp->private_data = NULL;
622 
623 	spin_lock_irq(&spidev->spi_lock);
624 	/* ... after we unbound from the underlying device? */
625 	dofree = (spidev->spi == NULL);
626 	spin_unlock_irq(&spidev->spi_lock);
627 
628 	/* last close? */
629 	spidev->users--;
630 	if (!spidev->users) {
631 
632 		kfree(spidev->tx_buffer);
633 		spidev->tx_buffer = NULL;
634 
635 		kfree(spidev->rx_buffer);
636 		spidev->rx_buffer = NULL;
637 
638 		if (dofree)
639 			kfree(spidev);
640 		else
641 			spidev->speed_hz = spidev->spi->max_speed_hz;
642 	}
643 #ifdef CONFIG_SPI_SLAVE
644 	if (!dofree)
645 		spi_slave_abort(spidev->spi);
646 #endif
647 	mutex_unlock(&device_list_lock);
648 
649 	return 0;
650 }
651 
652 static const struct file_operations spidev_fops = {
653 	.owner =	THIS_MODULE,
654 	/* REVISIT switch to aio primitives, so that userspace
655 	 * gets more complete API coverage.  It'll simplify things
656 	 * too, except for the locking.
657 	 */
658 	.write =	spidev_write,
659 	.read =		spidev_read,
660 	.unlocked_ioctl = spidev_ioctl,
661 	.compat_ioctl = spidev_compat_ioctl,
662 	.open =		spidev_open,
663 	.release =	spidev_release,
664 	.llseek =	no_llseek,
665 };
666 
667 /*-------------------------------------------------------------------------*/
668 
669 /* The main reason to have this class is to make mdev/udev create the
670  * /dev/spidevB.C character device nodes exposing our userspace API.
671  * It also simplifies memory management.
672  */
673 
674 static struct class *spidev_class;
675 
676 #ifdef CONFIG_OF
677 static const struct of_device_id spidev_dt_ids[] = {
678 	{ .compatible = "rohm,dh2228fv" },
679 	{ .compatible = "lineartechnology,ltc2488" },
680 	{ .compatible = "semtech,sx1301" },
681 	{ .compatible = "lwn,bk4" },
682 	{ .compatible = "dh,dhcom-board" },
683 	{ .compatible = "menlo,m53cpld" },
684 	{ .compatible = "cisco,spi-petra" },
685 	{ .compatible = "micron,spi-authenta" },
686 	{},
687 };
688 MODULE_DEVICE_TABLE(of, spidev_dt_ids);
689 #endif
690 
691 #ifdef CONFIG_ACPI
692 
693 /* Dummy SPI devices not to be used in production systems */
694 #define SPIDEV_ACPI_DUMMY	1
695 
696 static const struct acpi_device_id spidev_acpi_ids[] = {
697 	/*
698 	 * The ACPI SPT000* devices are only meant for development and
699 	 * testing. Systems used in production should have a proper ACPI
700 	 * description of the connected peripheral and they should also use
701 	 * a proper driver instead of poking directly to the SPI bus.
702 	 */
703 	{ "SPT0001", SPIDEV_ACPI_DUMMY },
704 	{ "SPT0002", SPIDEV_ACPI_DUMMY },
705 	{ "SPT0003", SPIDEV_ACPI_DUMMY },
706 	{},
707 };
708 MODULE_DEVICE_TABLE(acpi, spidev_acpi_ids);
709 
710 static void spidev_probe_acpi(struct spi_device *spi)
711 {
712 	const struct acpi_device_id *id;
713 
714 	if (!has_acpi_companion(&spi->dev))
715 		return;
716 
717 	id = acpi_match_device(spidev_acpi_ids, &spi->dev);
718 	if (WARN_ON(!id))
719 		return;
720 
721 	if (id->driver_data == SPIDEV_ACPI_DUMMY)
722 		dev_warn(&spi->dev, "do not use this driver in production systems!\n");
723 }
724 #else
725 static inline void spidev_probe_acpi(struct spi_device *spi) {}
726 #endif
727 
728 /*-------------------------------------------------------------------------*/
729 
730 static int spidev_probe(struct spi_device *spi)
731 {
732 	struct spidev_data	*spidev;
733 	int			status;
734 	unsigned long		minor;
735 
736 	/*
737 	 * spidev should never be referenced in DT without a specific
738 	 * compatible string, it is a Linux implementation thing
739 	 * rather than a description of the hardware.
740 	 */
741 	WARN(spi->dev.of_node &&
742 	     of_device_is_compatible(spi->dev.of_node, "spidev"),
743 	     "%pOF: buggy DT: spidev listed directly in DT\n", spi->dev.of_node);
744 
745 	spidev_probe_acpi(spi);
746 
747 	/* Allocate driver data */
748 	spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
749 	if (!spidev)
750 		return -ENOMEM;
751 
752 	/* Initialize the driver data */
753 	spidev->spi = spi;
754 	spin_lock_init(&spidev->spi_lock);
755 	mutex_init(&spidev->buf_lock);
756 
757 	INIT_LIST_HEAD(&spidev->device_entry);
758 
759 	/* If we can allocate a minor number, hook up this device.
760 	 * Reusing minors is fine so long as udev or mdev is working.
761 	 */
762 	mutex_lock(&device_list_lock);
763 	minor = find_first_zero_bit(minors, N_SPI_MINORS);
764 	if (minor < N_SPI_MINORS) {
765 		struct device *dev;
766 
767 		spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
768 		dev = device_create(spidev_class, &spi->dev, spidev->devt,
769 				    spidev, "spidev%d.%d",
770 				    spi->master->bus_num, spi->chip_select);
771 		status = PTR_ERR_OR_ZERO(dev);
772 	} else {
773 		dev_dbg(&spi->dev, "no minor number available!\n");
774 		status = -ENODEV;
775 	}
776 	if (status == 0) {
777 		set_bit(minor, minors);
778 		list_add(&spidev->device_entry, &device_list);
779 	}
780 	mutex_unlock(&device_list_lock);
781 
782 	spidev->speed_hz = spi->max_speed_hz;
783 
784 	if (status == 0)
785 		spi_set_drvdata(spi, spidev);
786 	else
787 		kfree(spidev);
788 
789 	return status;
790 }
791 
792 static int spidev_remove(struct spi_device *spi)
793 {
794 	struct spidev_data	*spidev = spi_get_drvdata(spi);
795 
796 	/* prevent new opens */
797 	mutex_lock(&device_list_lock);
798 	/* make sure ops on existing fds can abort cleanly */
799 	spin_lock_irq(&spidev->spi_lock);
800 	spidev->spi = NULL;
801 	spin_unlock_irq(&spidev->spi_lock);
802 
803 	list_del(&spidev->device_entry);
804 	device_destroy(spidev_class, spidev->devt);
805 	clear_bit(MINOR(spidev->devt), minors);
806 	if (spidev->users == 0)
807 		kfree(spidev);
808 	mutex_unlock(&device_list_lock);
809 
810 	return 0;
811 }
812 
813 static struct spi_driver spidev_spi_driver = {
814 	.driver = {
815 		.name =		"spidev",
816 		.of_match_table = of_match_ptr(spidev_dt_ids),
817 		.acpi_match_table = ACPI_PTR(spidev_acpi_ids),
818 	},
819 	.probe =	spidev_probe,
820 	.remove =	spidev_remove,
821 
822 	/* NOTE:  suspend/resume methods are not necessary here.
823 	 * We don't do anything except pass the requests to/from
824 	 * the underlying controller.  The refrigerator handles
825 	 * most issues; the controller driver handles the rest.
826 	 */
827 };
828 
829 /*-------------------------------------------------------------------------*/
830 
831 static int __init spidev_init(void)
832 {
833 	int status;
834 
835 	/* Claim our 256 reserved device numbers.  Then register a class
836 	 * that will key udev/mdev to add/remove /dev nodes.  Last, register
837 	 * the driver which manages those device numbers.
838 	 */
839 	BUILD_BUG_ON(N_SPI_MINORS > 256);
840 	status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
841 	if (status < 0)
842 		return status;
843 
844 	spidev_class = class_create(THIS_MODULE, "spidev");
845 	if (IS_ERR(spidev_class)) {
846 		unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
847 		return PTR_ERR(spidev_class);
848 	}
849 
850 	status = spi_register_driver(&spidev_spi_driver);
851 	if (status < 0) {
852 		class_destroy(spidev_class);
853 		unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
854 	}
855 	return status;
856 }
857 module_init(spidev_init);
858 
859 static void __exit spidev_exit(void)
860 {
861 	spi_unregister_driver(&spidev_spi_driver);
862 	class_destroy(spidev_class);
863 	unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
864 }
865 module_exit(spidev_exit);
866 
867 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
868 MODULE_DESCRIPTION("User mode SPI device interface");
869 MODULE_LICENSE("GPL");
870 MODULE_ALIAS("spi:spidev");
871