summaryrefslogtreecommitdiff
path: root/drivers/spi/spidev.c
blob: 1935ca61344706a60f9c497d8d2c4052414fe12d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Simple synchronous userspace interface to SPI devices
 *
 * Copyright (C) 2006 SWAPP
 *	Andrea Paterniani <a.paterniani@swapp-eng.it>
 * Copyright (C) 2007 David Brownell (simplification, cleanup)
 */

#include <linux/init.h>
#include <linux/ioctl.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/list.h>
#include <linux/errno.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/property.h>
#include <linux/slab.h>
#include <linux/compat.h>

#include <linux/spi/spi.h>
#include <linux/spi/spidev.h>

#include <linux/uaccess.h>


/*
 * This supports access to SPI devices using normal userspace I/O calls.
 * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
 * and often mask message boundaries, full SPI support requires full duplex
 * transfers.  There are several kinds of internal message boundaries to
 * handle chipselect management and other protocol options.
 *
 * SPI has a character major number assigned.  We allocate minor numbers
 * dynamically using a bitmask.  You must use hotplug tools, such as udev
 * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
 * nodes, since there is no fixed association of minor numbers with any
 * particular SPI bus or device.
 */
#define SPIDEV_MAJOR			153	/* assigned */
#define N_SPI_MINORS			32	/* ... up to 256 */

static DECLARE_BITMAP(minors, N_SPI_MINORS);

static_assert(N_SPI_MINORS > 0 && N_SPI_MINORS <= 256);

/* Bit masks for spi_device.mode management.  Note that incorrect
 * settings for some settings can cause *lots* of trouble for other
 * devices on a shared bus:
 *
 *  - CS_HIGH ... this device will be active when it shouldn't be
 *  - 3WIRE ... when active, it won't behave as it should
 *  - NO_CS ... there will be no explicit message boundaries; this
 *	is completely incompatible with the shared bus model
 *  - READY ... transfers may proceed when they shouldn't.
 *
 * REVISIT should changing those flags be privileged?
 */
#define SPI_MODE_MASK		(SPI_MODE_X_MASK | SPI_CS_HIGH \
				| SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \
				| SPI_NO_CS | SPI_READY | SPI_TX_DUAL \
				| SPI_TX_QUAD | SPI_TX_OCTAL | SPI_RX_DUAL \
				| SPI_RX_QUAD | SPI_RX_OCTAL \
				| SPI_RX_CPHA_FLIP)

struct spidev_data {
	dev_t			devt;
	struct mutex		spi_lock;
	struct spi_device	*spi;
	struct list_head	device_entry;

	/* TX/RX buffers are NULL unless this device is open (users > 0) */
	struct mutex		buf_lock;
	unsigned		users;
	u8			*tx_buffer;
	u8			*rx_buffer;
	u32			speed_hz;
};

static LIST_HEAD(device_list);
static DEFINE_MUTEX(device_list_lock);

static unsigned bufsiz = 4096;
module_param(bufsiz, uint, S_IRUGO);
MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");

/*-------------------------------------------------------------------------*/

static ssize_t
spidev_sync(struct spidev_data *spidev, struct spi_message *message)
{
	int status;
	struct spi_device *spi;

	mutex_lock(&spidev->spi_lock);
	spi = spidev->spi;

	if (spi == NULL)
		status = -ESHUTDOWN;
	else
		status = spi_sync(spi, message);

	if (status == 0)
		status = message->actual_length;

	mutex_unlock(&spidev->spi_lock);
	return status;
}

static inline ssize_t
spidev_sync_write(struct spidev_data *spidev, size_t len)
{
	struct spi_transfer	t = {
			.tx_buf		= spidev->tx_buffer,
			.len		= len,
			.speed_hz	= spidev->speed_hz,
		};
	struct spi_message	m;

	spi_message_init(&m);
	spi_message_add_tail(&t, &m);
	return spidev_sync(spidev, &m);
}

static inline ssize_t
spidev_sync_read(struct spidev_data *spidev, size_t len)
{
	struct spi_transfer	t = {
			.rx_buf		= spidev->rx_buffer,
			.len		= len,
			.speed_hz	= spidev->speed_hz,
		};
	struct spi_message	m;

	spi_message_init(&m);
	spi_message_add_tail(&t, &m);
	return spidev_sync(spidev, &m);
}

/*-------------------------------------------------------------------------*/

/* Read-only message with current device setup */
static ssize_t
spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
	struct spidev_data	*spidev;
	ssize_t			status;

	/* chipselect only toggles at start or end of operation */
	if (count > bufsiz)
		return -EMSGSIZE;

	spidev = filp->private_data;

	mutex_lock(&spidev->buf_lock);
	status = spidev_sync_read(spidev, count);
	if (status > 0) {
		unsigned long	missing;

		missing = copy_to_user(buf, spidev->rx_buffer, status);
		if (missing == status)
			status = -EFAULT;
		else
			status = status - missing;
	}
	mutex_unlock(&spidev->buf_lock);

	return status;
}

/* Write-only message with current device setup */
static ssize_t
spidev_write(struct file *filp, const char __user *buf,
		size_t count, loff_t *f_pos)
{
	struct spidev_data	*spidev;
	ssize_t			status;
	unsigned long		missing;

	/* chipselect only toggles at start or end of operation */
	if (count > bufsiz)
		return -EMSGSIZE;

	spidev = filp->private_data;

	mutex_lock(&spidev->buf_lock);
	missing = copy_from_user(spidev->tx_buffer, buf, count);
	if (missing == 0)
		status = spidev_sync_write(spidev, count);
	else
		status = -EFAULT;
	mutex_unlock(&spidev->buf_lock);

	return status;
}

static int spidev_message(struct spidev_data *spidev,
		struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
{
	struct spi_message	msg;
	struct spi_transfer	*k_xfers;
	struct spi_transfer	*k_tmp;
	struct spi_ioc_transfer *u_tmp;
	unsigned		n, total, tx_total, rx_total;
	u8			*tx_buf, *rx_buf;
	int			status = -EFAULT;

	spi_message_init(&msg);
	k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
	if (k_xfers == NULL)
		return -ENOMEM;

	/* Construct spi_message, copying any tx data to bounce buffer.
	 * We walk the array of user-provided transfers, using each one
	 * to initialize a kernel version of the same transfer.
	 */
	tx_buf = spidev->tx_buffer;
	rx_buf = spidev->rx_buffer;
	total = 0;
	tx_total = 0;
	rx_total = 0;
	for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
			n;
			n--, k_tmp++, u_tmp++) {
		/* Ensure that also following allocations from rx_buf/tx_buf will meet
		 * DMA alignment requirements.
		 */
		unsigned int len_aligned = ALIGN(u_tmp->len, ARCH_KMALLOC_MINALIGN);

		k_tmp->len = u_tmp->len;

		total += k_tmp->len;
		/* Since the function returns the total length of transfers
		 * on success, restrict the total to positive int values to
		 * avoid the return value looking like an error.  Also check
		 * each transfer length to avoid arithmetic overflow.
		 */
		if (total > INT_MAX || k_tmp->len > INT_MAX) {
			status = -EMSGSIZE;
			goto done;
		}

		if (u_tmp->rx_buf) {
			/* this transfer needs space in RX bounce buffer */
			rx_total += len_aligned;
			if (rx_total > bufsiz) {
				status = -EMSGSIZE;
				goto done;
			}
			k_tmp->rx_buf = rx_buf;
			rx_buf += len_aligned;
		}
		if (u_tmp->tx_buf) {
			/* this transfer needs space in TX bounce buffer */
			tx_total += len_aligned;
			if (tx_total > bufsiz) {
				status = -EMSGSIZE;
				goto done;
			}
			k_tmp->tx_buf = tx_buf;
			if (copy_from_user(tx_buf, (const u8 __user *)
						(uintptr_t) u_tmp->tx_buf,
					u_tmp->len))
				goto done;
			tx_buf += len_aligned;
		}

		k_tmp->cs_change = !!u_tmp->cs_change;
		k_tmp->tx_nbits = u_tmp->tx_nbits;
		k_tmp->rx_nbits = u_tmp->rx_nbits;
		k_tmp->bits_per_word = u_tmp->bits_per_word;
		k_tmp->delay.value = u_tmp->delay_usecs;
		k_tmp->delay.unit = SPI_DELAY_UNIT_USECS;
		k_tmp->speed_hz = u_tmp->speed_hz;
		k_tmp->word_delay.value = u_tmp->word_delay_usecs;
		k_tmp->word_delay.unit = SPI_DELAY_UNIT_USECS;
		if (!k_tmp->speed_hz)
			k_tmp->speed_hz = spidev->speed_hz;
#ifdef VERBOSE
		dev_dbg(&spidev->spi->dev,
			"  xfer len %u %s%s%s%dbits %u usec %u usec %uHz\n",
			k_tmp->len,
			k_tmp->rx_buf ? "rx " : "",
			k_tmp->tx_buf ? "tx " : "",
			k_tmp->cs_change ? "cs " : "",
			k_tmp->bits_per_word ? : spidev->spi->bits_per_word,
			k_tmp->delay.value,
			k_tmp->word_delay.value,
			k_tmp->speed_hz ? : spidev->spi->max_speed_hz);
#endif
		spi_message_add_tail(k_tmp, &msg);
	}

	status = spidev_sync(spidev, &msg);
	if (status < 0)
		goto done;

	/* copy any rx data out of bounce buffer */
	for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
			n;
			n--, k_tmp++, u_tmp++) {
		if (u_tmp->rx_buf) {
			if (copy_to_user((u8 __user *)
					(uintptr_t) u_tmp->rx_buf, k_tmp->rx_buf,
					u_tmp->len)) {
				status = -EFAULT;
				goto done;
			}
		}
	}
	status = total;

done:
	kfree(k_xfers);
	return status;
}

static struct spi_ioc_transfer *
spidev_get_ioc_message(unsigned int cmd, struct spi_ioc_transfer __user *u_ioc,
		unsigned *n_ioc)
{
	u32	tmp;

	/* Check type, command number and direction */
	if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC
			|| _IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
			|| _IOC_DIR(cmd) != _IOC_WRITE)
		return ERR_PTR(-ENOTTY);

	tmp = _IOC_SIZE(cmd);
	if ((tmp % sizeof(struct spi_ioc_transfer)) != 0)
		return ERR_PTR(-EINVAL);
	*n_ioc = tmp / sizeof(struct spi_ioc_transfer);
	if (*n_ioc == 0)
		return NULL;

	/* copy into scratch area */
	return memdup_user(u_ioc, tmp);
}

static long
spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
	int			retval = 0;
	struct spidev_data	*spidev;
	struct spi_device	*spi;
	u32			tmp;
	unsigned		n_ioc;
	struct spi_ioc_transfer	*ioc;

	/* Check type and command number */
	if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
		return -ENOTTY;

	/* guard against device removal before, or while,
	 * we issue this ioctl.
	 */
	spidev = filp->private_data;
	mutex_lock(&spidev->spi_lock);
	spi = spi_dev_get(spidev->spi);
	if (spi == NULL) {
		mutex_unlock(&spidev->spi_lock);
		return -ESHUTDOWN;
	}

	/* use the buffer lock here for triple duty:
	 *  - prevent I/O (from us) so calling spi_setup() is safe;
	 *  - prevent concurrent SPI_IOC_WR_* from morphing
	 *    data fields while SPI_IOC_RD_* reads them;
	 *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
	 */
	mutex_lock(&spidev->buf_lock);

	switch (cmd) {
	/* read requests */
	case SPI_IOC_RD_MODE:
	case SPI_IOC_RD_MODE32:
		tmp = spi->mode;

		{
			struct spi_controller *ctlr = spi->controller;

			if (ctlr->use_gpio_descriptors && ctlr->cs_gpiods &&
			    ctlr->cs_gpiods[spi->chip_select])
				tmp &= ~SPI_CS_HIGH;
		}

		if (cmd == SPI_IOC_RD_MODE)
			retval = put_user(tmp & SPI_MODE_MASK,
					  (__u8 __user *)arg);
		else
			retval = put_user(tmp & SPI_MODE_MASK,
					  (__u32 __user *)arg);
		break;
	case SPI_IOC_RD_LSB_FIRST:
		retval = put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
					(__u8 __user *)arg);
		break;
	case SPI_IOC_RD_BITS_PER_WORD:
		retval = put_user(spi->bits_per_word, (__u8 __user *)arg);
		break;
	case SPI_IOC_RD_MAX_SPEED_HZ:
		retval = put_user(spidev->speed_hz, (__u32 __user *)arg);
		break;

	/* write requests */
	case SPI_IOC_WR_MODE:
	case SPI_IOC_WR_MODE32:
		if (cmd == SPI_IOC_WR_MODE)
			retval = get_user(tmp, (u8 __user *)arg);
		else
			retval = get_user(tmp, (u32 __user *)arg);
		if (retval == 0) {
			struct spi_controller *ctlr = spi->controller;
			u32	save = spi->mode;

			if (tmp & ~SPI_MODE_MASK) {
				retval = -EINVAL;
				break;
			}

			if (ctlr->use_gpio_descriptors && ctlr->cs_gpiods &&
			    ctlr->cs_gpiods[spi->chip_select])
				tmp |= SPI_CS_HIGH;

			tmp |= spi->mode & ~SPI_MODE_MASK;
			spi->mode = tmp & SPI_MODE_USER_MASK;
			retval = spi_setup(spi);
			if (retval < 0)
				spi->mode = save;
			else
				dev_dbg(&spi->dev, "spi mode %x\n", tmp);
		}
		break;
	case SPI_IOC_WR_LSB_FIRST:
		retval = get_user(tmp, (__u8 __user *)arg);
		if (retval == 0) {
			u32	save = spi->mode;

			if (tmp)
				spi->mode |= SPI_LSB_FIRST;
			else
				spi->mode &= ~SPI_LSB_FIRST;
			retval = spi_setup(spi);
			if (retval < 0)
				spi->mode = save;
			else
				dev_dbg(&spi->dev, "%csb first\n",
						tmp ? 'l' : 'm');
		}
		break;
	case SPI_IOC_WR_BITS_PER_WORD:
		retval = get_user(tmp, (__u8 __user *)arg);
		if (retval == 0) {
			u8	save = spi->bits_per_word;

			spi->bits_per_word = tmp;
			retval = spi_setup(spi);
			if (retval < 0)
				spi->bits_per_word = save;
			else
				dev_dbg(&spi->dev, "%d bits per word\n", tmp);
		}
		break;
	case SPI_IOC_WR_MAX_SPEED_HZ: {
		u32 save;

		retval = get_user(tmp, (__u32 __user *)arg);
		if (retval)
			break;
		if (tmp == 0) {
			retval = -EINVAL;
			break;
		}

		save = spi->max_speed_hz;

		spi->max_speed_hz = tmp;
		retval = spi_setup(spi);
		if (retval == 0) {
			spidev->speed_hz = tmp;
			dev_dbg(&spi->dev, "%d Hz (max)\n", spidev->speed_hz);
		}

		spi->max_speed_hz = save;
		break;
	}
	default:
		/* segmented and/or full-duplex I/O request */
		/* Check message and copy into scratch area */
		ioc = spidev_get_ioc_message(cmd,
				(struct spi_ioc_transfer __user *)arg, &n_ioc);
		if (IS_ERR(ioc)) {
			retval = PTR_ERR(ioc);
			break;
		}
		if (!ioc)
			break;	/* n_ioc is also 0 */

		/* translate to spi_message, execute */
		retval = spidev_message(spidev, ioc, n_ioc);
		kfree(ioc);
		break;
	}

	mutex_unlock(&spidev->buf_lock);
	spi_dev_put(spi);
	mutex_unlock(&spidev->spi_lock);
	return retval;
}

#ifdef CONFIG_COMPAT
static long
spidev_compat_ioc_message(struct file *filp, unsigned int cmd,
		unsigned long arg)
{
	struct spi_ioc_transfer __user	*u_ioc;
	int				retval = 0;
	struct spidev_data		*spidev;
	struct spi_device		*spi;
	unsigned			n_ioc, n;
	struct spi_ioc_transfer		*ioc;

	u_ioc = (struct spi_ioc_transfer __user *) compat_ptr(arg);

	/* guard against device removal before, or while,
	 * we issue this ioctl.
	 */
	spidev = filp->private_data;
	mutex_lock(&spidev->spi_lock);
	spi = spi_dev_get(spidev->spi);
	if (spi == NULL) {
		mutex_unlock(&spidev->spi_lock);
		return -ESHUTDOWN;
	}

	/* SPI_IOC_MESSAGE needs the buffer locked "normally" */
	mutex_lock(&spidev->buf_lock);

	/* Check message and copy into scratch area */
	ioc = spidev_get_ioc_message(cmd, u_ioc, &n_ioc);
	if (IS_ERR(ioc)) {
		retval = PTR_ERR(ioc);
		goto done;
	}
	if (!ioc)
		goto done;	/* n_ioc is also 0 */

	/* Convert buffer pointers */
	for (n = 0; n < n_ioc; n++) {
		ioc[n].rx_buf = (uintptr_t) compat_ptr(ioc[n].rx_buf);
		ioc[n].tx_buf = (uintptr_t) compat_ptr(ioc[n].tx_buf);
	}

	/* translate to spi_message, execute */
	retval = spidev_message(spidev, ioc, n_ioc);
	kfree(ioc);

done:
	mutex_unlock(&spidev->buf_lock);
	spi_dev_put(spi);
	mutex_unlock(&spidev->spi_lock);
	return retval;
}

static long
spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
	if (_IOC_TYPE(cmd) == SPI_IOC_MAGIC
			&& _IOC_NR(cmd) == _IOC_NR(SPI_IOC_MESSAGE(0))
			&& _IOC_DIR(cmd) == _IOC_WRITE)
		return spidev_compat_ioc_message(filp, cmd, arg);

	return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
}
#else
#define spidev_compat_ioctl NULL
#endif /* CONFIG_COMPAT */

static int spidev_open(struct inode *inode, struct file *filp)
{
	struct spidev_data	*spidev = NULL, *iter;
	int			status = -ENXIO;

	mutex_lock(&device_list_lock);

	list_for_each_entry(iter, &device_list, device_entry) {
		if (iter->devt == inode->i_rdev) {
			status = 0;
			spidev = iter;
			break;
		}
	}

	if (!spidev) {
		pr_debug("spidev: nothing for minor %d\n", iminor(inode));
		goto err_find_dev;
	}

	if (!spidev->tx_buffer) {
		spidev->tx_buffer = kmalloc(bufsiz, GFP_KERNEL);
		if (!spidev->tx_buffer) {
			status = -ENOMEM;
			goto err_find_dev;
		}
	}

	if (!spidev->rx_buffer) {
		spidev->rx_buffer = kmalloc(bufsiz, GFP_KERNEL);
		if (!spidev->rx_buffer) {
			status = -ENOMEM;
			goto err_alloc_rx_buf;
		}
	}

	spidev->users++;
	filp->private_data = spidev;
	stream_open(inode, filp);

	mutex_unlock(&device_list_lock);
	return 0;

err_alloc_rx_buf:
	kfree(spidev->tx_buffer);
	spidev->tx_buffer = NULL;
err_find_dev:
	mutex_unlock(&device_list_lock);
	return status;
}

static int spidev_release(struct inode *inode, struct file *filp)
{
	struct spidev_data	*spidev;
	int			dofree;

	mutex_lock(&device_list_lock);
	spidev = filp->private_data;
	filp->private_data = NULL;

	mutex_lock(&spidev->spi_lock);
	/* ... after we unbound from the underlying device? */
	dofree = (spidev->spi == NULL);
	mutex_unlock(&spidev->spi_lock);

	/* last close? */
	spidev->users--;
	if (!spidev->users) {

		kfree(spidev->tx_buffer);
		spidev->tx_buffer = NULL;

		kfree(spidev->rx_buffer);
		spidev->rx_buffer = NULL;

		if (dofree)
			kfree(spidev);
		else
			spidev->speed_hz = spidev->spi->max_speed_hz;
	}
#ifdef CONFIG_SPI_SLAVE
	if (!dofree)
		spi_slave_abort(spidev->spi);
#endif
	mutex_unlock(&device_list_lock);

	return 0;
}

static const struct file_operations spidev_fops = {
	.owner =	THIS_MODULE,
	/* REVISIT switch to aio primitives, so that userspace
	 * gets more complete API coverage.  It'll simplify things
	 * too, except for the locking.
	 */
	.write =	spidev_write,
	.read =		spidev_read,
	.unlocked_ioctl = spidev_ioctl,
	.compat_ioctl = spidev_compat_ioctl,
	.open =		spidev_open,
	.release =	spidev_release,
	.llseek =	no_llseek,
};

/*-------------------------------------------------------------------------*/

/* The main reason to have this class is to make mdev/udev create the
 * /dev/spidevB.C character device nodes exposing our userspace API.
 * It also simplifies memory management.
 */

static struct class *spidev_class;

static const struct spi_device_id spidev_spi_ids[] = {
	{ .name = "dh2228fv" },
	{ .name = "ltc2488" },
	{ .name = "sx1301" },
	{ .name = "bk4" },
	{ .name = "dhcom-board" },
	{ .name = "m53cpld" },
	{ .name = "spi-petra" },
	{ .name = "spi-authenta" },
	{},
};
MODULE_DEVICE_TABLE(spi, spidev_spi_ids);

/*
 * spidev should never be referenced in DT without a specific compatible string,
 * it is a Linux implementation thing rather than a description of the hardware.
 */
static int spidev_of_check(struct device *dev)
{
	if (device_property_match_string(dev, "compatible", "spidev") < 0)
		return 0;

	dev_err(dev, "spidev listed directly in DT is not supported\n");
	return -EINVAL;
}

static const struct of_device_id spidev_dt_ids[] = {
	{ .compatible = "rohm,dh2228fv", .data = &spidev_of_check },
	{ .compatible = "lineartechnology,ltc2488", .data = &spidev_of_check },
	{ .compatible = "semtech,sx1301", .data = &spidev_of_check },
	{ .compatible = "lwn,bk4", .data = &spidev_of_check },
	{ .compatible = "dh,dhcom-board", .data = &spidev_of_check },
	{ .compatible = "menlo,m53cpld", .data = &spidev_of_check },
	{ .compatible = "cisco,spi-petra", .data = &spidev_of_check },
	{ .compatible = "micron,spi-authenta", .data = &spidev_of_check },
	{},
};
MODULE_DEVICE_TABLE(of, spidev_dt_ids);

/* Dummy SPI devices not to be used in production systems */
static int spidev_acpi_check(struct device *dev)
{
	dev_warn(dev, "do not use this driver in production systems!\n");
	return 0;
}

static const struct acpi_device_id spidev_acpi_ids[] = {
	/*
	 * The ACPI SPT000* devices are only meant for development and
	 * testing. Systems used in production should have a proper ACPI
	 * description of the connected peripheral and they should also use
	 * a proper driver instead of poking directly to the SPI bus.
	 */
	{ "SPT0001", (kernel_ulong_t)&spidev_acpi_check },
	{ "SPT0002", (kernel_ulong_t)&spidev_acpi_check },
	{ "SPT0003", (kernel_ulong_t)&spidev_acpi_check },
	{},
};
MODULE_DEVICE_TABLE(acpi, spidev_acpi_ids);

/*-------------------------------------------------------------------------*/

static int spidev_probe(struct spi_device *spi)
{
	int (*match)(struct device *dev);
	struct spidev_data	*spidev;
	int			status;
	unsigned long		minor;

	match = device_get_match_data(&spi->dev);
	if (match) {
		status = match(&spi->dev);
		if (status)
			return status;
	}

	/* Allocate driver data */
	spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
	if (!spidev)
		return -ENOMEM;

	/* Initialize the driver data */
	spidev->spi = spi;
	mutex_init(&spidev->spi_lock);
	mutex_init(&spidev->buf_lock);

	INIT_LIST_HEAD(&spidev->device_entry);

	/* If we can allocate a minor number, hook up this device.
	 * Reusing minors is fine so long as udev or mdev is working.
	 */
	mutex_lock(&device_list_lock);
	minor = find_first_zero_bit(minors, N_SPI_MINORS);
	if (minor < N_SPI_MINORS) {
		struct device *dev;

		spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
		dev = device_create(spidev_class, &spi->dev, spidev->devt,
				    spidev, "spidev%d.%d",
				    spi->master->bus_num, spi->chip_select);
		status = PTR_ERR_OR_ZERO(dev);
	} else {
		dev_dbg(&spi->dev, "no minor number available!\n");
		status = -ENODEV;
	}
	if (status == 0) {
		set_bit(minor, minors);
		list_add(&spidev->device_entry, &device_list);
	}
	mutex_unlock(&device_list_lock);

	spidev->speed_hz = spi->max_speed_hz;

	if (status == 0)
		spi_set_drvdata(spi, spidev);
	else
		kfree(spidev);

	return status;
}

static void spidev_remove(struct spi_device *spi)
{
	struct spidev_data	*spidev = spi_get_drvdata(spi);

	/* prevent new opens */
	mutex_lock(&device_list_lock);
	/* make sure ops on existing fds can abort cleanly */
	mutex_lock(&spidev->spi_lock);
	spidev->spi = NULL;
	mutex_unlock(&spidev->spi_lock);

	list_del(&spidev->device_entry);
	device_destroy(spidev_class, spidev->devt);
	clear_bit(MINOR(spidev->devt), minors);
	if (spidev->users == 0)
		kfree(spidev);
	mutex_unlock(&device_list_lock);
}

static struct spi_driver spidev_spi_driver = {
	.driver = {
		.name =		"spidev",
		.of_match_table = spidev_dt_ids,
		.acpi_match_table = spidev_acpi_ids,
	},
	.probe =	spidev_probe,
	.remove =	spidev_remove,
	.id_table =	spidev_spi_ids,

	/* NOTE:  suspend/resume methods are not necessary here.
	 * We don't do anything except pass the requests to/from
	 * the underlying controller.  The refrigerator handles
	 * most issues; the controller driver handles the rest.
	 */
};

/*-------------------------------------------------------------------------*/

static int __init spidev_init(void)
{
	int status;

	/* Claim our 256 reserved device numbers.  Then register a class
	 * that will key udev/mdev to add/remove /dev nodes.  Last, register
	 * the driver which manages those device numbers.
	 */
	status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
	if (status < 0)
		return status;

	spidev_class = class_create(THIS_MODULE, "spidev");
	if (IS_ERR(spidev_class)) {
		unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
		return PTR_ERR(spidev_class);
	}

	status = spi_register_driver(&spidev_spi_driver);
	if (status < 0) {
		class_destroy(spidev_class);
		unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
	}
	return status;
}
module_init(spidev_init);

static void __exit spidev_exit(void)
{
	spi_unregister_driver(&spidev_spi_driver);
	class_destroy(spidev_class);
	unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
}
module_exit(spidev_exit);

MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
MODULE_DESCRIPTION("User mode SPI device interface");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:spidev");