aboutsummaryrefslogtreecommitdiff
path: root/drivers/spi/spi.c
blob: b02d0cbce89049e003fe8300421adeed847e92ce (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
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
/*
 * spi.c - SPI init/core code
 *
 * Copyright (C) 2005 David Brownell
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/cache.h>
#include <linux/mutex.h>
#include <linux/of_device.h>
#include <linux/slab.h>
#include <linux/mod_devicetable.h>
#include <linux/spi/spi.h>
#include <linux/of_spi.h>

static void spidev_release(struct device *dev)
{
	struct spi_device	*spi = to_spi_device(dev);

	/* spi masters may cleanup for released devices */
	if (spi->master->cleanup)
		spi->master->cleanup(spi);

	spi_master_put(spi->master);
	kfree(spi);
}

static ssize_t
modalias_show(struct device *dev, struct device_attribute *a, char *buf)
{
	const struct spi_device	*spi = to_spi_device(dev);

	return sprintf(buf, "%s\n", spi->modalias);
}

static struct device_attribute spi_dev_attrs[] = {
	__ATTR_RO(modalias),
	__ATTR_NULL,
};

/* modalias support makes "modprobe $MODALIAS" new-style hotplug work,
 * and the sysfs version makes coldplug work too.
 */

static const struct spi_device_id *spi_match_id(const struct spi_device_id *id,
						const struct spi_device *sdev)
{
	while (id->name[0]) {
		if (!strcmp(sdev->modalias, id->name))
			return id;
		id++;
	}
	return NULL;
}

const struct spi_device_id *spi_get_device_id(const struct spi_device *sdev)
{
	const struct spi_driver *sdrv = to_spi_driver(sdev->dev.driver);

	return spi_match_id(sdrv->id_table, sdev);
}
EXPORT_SYMBOL_GPL(spi_get_device_id);

static int spi_match_device(struct device *dev, struct device_driver *drv)
{
	const struct spi_device	*spi = to_spi_device(dev);
	const struct spi_driver	*sdrv = to_spi_driver(drv);

	/* Attempt an OF style match */
	if (of_driver_match_device(dev, drv))
		return 1;

	if (sdrv->id_table)
		return !!spi_match_id(sdrv->id_table, spi);

	return strcmp(spi->modalias, drv->name) == 0;
}

static int spi_uevent(struct device *dev, struct kobj_uevent_env *env)
{
	const struct spi_device		*spi = to_spi_device(dev);

	add_uevent_var(env, "MODALIAS=%s%s", SPI_MODULE_PREFIX, spi->modalias);
	return 0;
}

#ifdef	CONFIG_PM

static int spi_suspend(struct device *dev, pm_message_t message)
{
	int			value = 0;
	struct spi_driver	*drv = to_spi_driver(dev->driver);

	/* suspend will stop irqs and dma; no more i/o */
	if (drv) {
		if (drv->suspend)
			value = drv->suspend(to_spi_device(dev), message);
		else
			dev_dbg(dev, "... can't suspend\n");
	}
	return value;
}

static int spi_resume(struct device *dev)
{
	int			value = 0;
	struct spi_driver	*drv = to_spi_driver(dev->driver);

	/* resume may restart the i/o queue */
	if (drv) {
		if (drv->resume)
			value = drv->resume(to_spi_device(dev));
		else
			dev_dbg(dev, "... can't resume\n");
	}
	return value;
}

#else
#define spi_suspend	NULL
#define spi_resume	NULL
#endif

struct bus_type spi_bus_type = {
	.name		= "spi",
	.dev_attrs	= spi_dev_attrs,
	.match		= spi_match_device,
	.uevent		= spi_uevent,
	.suspend	= spi_suspend,
	.resume		= spi_resume,
};
EXPORT_SYMBOL_GPL(spi_bus_type);


static int spi_drv_probe(struct device *dev)
{
	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);

	return sdrv->probe(to_spi_device(dev));
}

static int spi_drv_remove(struct device *dev)
{
	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);

	return sdrv->remove(to_spi_device(dev));
}

static void spi_drv_shutdown(struct device *dev)
{
	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);

	sdrv->shutdown(to_spi_device(dev));
}

/**
 * spi_register_driver - register a SPI driver
 * @sdrv: the driver to register
 * Context: can sleep
 */
int spi_register_driver(struct spi_driver *sdrv)
{
	sdrv->driver.bus = &spi_bus_type;
	if (sdrv->probe)
		sdrv->driver.probe = spi_drv_probe;
	if (sdrv->remove)
		sdrv->driver.remove = spi_drv_remove;
	if (sdrv->shutdown)
		sdrv->driver.shutdown = spi_drv_shutdown;
	return driver_register(&sdrv->driver);
}
EXPORT_SYMBOL_GPL(spi_register_driver);

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

/* SPI devices should normally not be created by SPI device drivers; that
 * would make them board-specific.  Similarly with SPI master drivers.
 * Device registration normally goes into like arch/.../mach.../board-YYY.c
 * with other readonly (flashable) information about mainboard devices.
 */

struct boardinfo {
	struct list_head	list;
	struct spi_board_info	board_info;
};

static LIST_HEAD(board_list);
static LIST_HEAD(spi_master_list);

/*
 * Used to protect add/del opertion for board_info list and
 * spi_master list, and their matching process
 */
static DEFINE_MUTEX(board_lock);

/**
 * spi_alloc_device - Allocate a new SPI device
 * @master: Controller to which device is connected
 * Context: can sleep
 *
 * Allows a driver to allocate and initialize a spi_device without
 * registering it immediately.  This allows a driver to directly
 * fill the spi_device with device parameters before calling
 * spi_add_device() on it.
 *
 * Caller is responsible to call spi_add_device() on the returned
 * spi_device structure to add it to the SPI master.  If the caller
 * needs to discard the spi_device without adding it, then it should
 * call spi_dev_put() on it.
 *
 * Returns a pointer to the new device, or NULL.
 */
struct spi_device *spi_alloc_device(struct spi_master *master)
{
	struct spi_device	*spi;
	struct device		*dev = master->dev.parent;

	if (!spi_master_get(master))
		return NULL;

	spi = kzalloc(sizeof *spi, GFP_KERNEL);
	if (!spi) {
		dev_err(dev, "cannot alloc spi_device\n");
		spi_master_put(master);
		return NULL;
	}

	spi->master = master;
	spi->dev.parent = dev;
	spi->dev.bus = &spi_bus_type;
	spi->dev.release = spidev_release;
	device_initialize(&spi->dev);
	return spi;
}
EXPORT_SYMBOL_GPL(spi_alloc_device);

/**
 * spi_add_device - Add spi_device allocated with spi_alloc_device
 * @spi: spi_device to register
 *
 * Companion function to spi_alloc_device.  Devices allocated with
 * spi_alloc_device can be added onto the spi bus with this function.
 *
 * Returns 0 on success; negative errno on failure
 */
int spi_add_device(struct spi_device *spi)
{
	static DEFINE_MUTEX(spi_add_lock);
	struct device *dev = spi->master->dev.parent;
	struct device *d;
	int status;

	/* Chipselects are numbered 0..max; validate. */
	if (spi->chip_select >= spi->master->num_chipselect) {
		dev_err(dev, "cs%d >= max %d\n",
			spi->chip_select,
			spi->master->num_chipselect);
		return -EINVAL;
	}

	/* Set the bus ID string */
	dev_set_name(&spi->dev, "%s.%u", dev_name(&spi->master->dev),
			spi->chip_select);


	/* We need to make sure there's no other device with this
	 * chipselect **BEFORE** we call setup(), else we'll trash
	 * its configuration.  Lock against concurrent add() calls.
	 */
	mutex_lock(&spi_add_lock);

	d = bus_find_device_by_name(&spi_bus_type, NULL, dev_name(&spi->dev));
	if (d != NULL) {
		dev_err(dev, "chipselect %d already in use\n",
				spi->chip_select);
		put_device(d);
		status = -EBUSY;
		goto done;
	}

	/* Drivers may modify this initial i/o setup, but will
	 * normally rely on the device being setup.  Devices
	 * using SPI_CS_HIGH can't coexist well otherwise...
	 */
	status = spi_setup(spi);
	if (status < 0) {
		dev_err(dev, "can't setup %s, status %d\n",
				dev_name(&spi->dev), status);
		goto done;
	}

	/* Device may be bound to an active driver when this returns */
	status = device_add(&spi->dev);
	if (status < 0)
		dev_err(dev, "can't add %s, status %d\n",
				dev_name(&spi->dev), status);
	else
		dev_dbg(dev, "registered child %s\n", dev_name(&spi->dev));

done:
	mutex_unlock(&spi_add_lock);
	return status;
}
EXPORT_SYMBOL_GPL(spi_add_device);

/**
 * spi_new_device - instantiate one new SPI device
 * @master: Controller to which device is connected
 * @chip: Describes the SPI device
 * Context: can sleep
 *
 * On typical mainboards, this is purely internal; and it's not needed
 * after board init creates the hard-wired devices.  Some development
 * platforms may not be able to use spi_register_board_info though, and
 * this is exported so that for example a USB or parport based adapter
 * driver could add devices (which it would learn about out-of-band).
 *
 * Returns the new device, or NULL.
 */
struct spi_device *spi_new_device(struct spi_master *master,
				  struct spi_board_info *chip)
{
	struct spi_device	*proxy;
	int			status;

	/* NOTE:  caller did any chip->bus_num checks necessary.
	 *
	 * Also, unless we change the return value convention to use
	 * error-or-pointer (not NULL-or-pointer), troubleshootability
	 * suggests syslogged diagnostics are best here (ugh).
	 */

	proxy = spi_alloc_device(master);
	if (!proxy)
		return NULL;

	WARN_ON(strlen(chip->modalias) >= sizeof(proxy->modalias));

	proxy->chip_select = chip->chip_select;
	proxy->max_speed_hz = chip->max_speed_hz;
	proxy->mode = chip->mode;
	proxy->irq = chip->irq;
	strlcpy(proxy->modalias, chip->modalias, sizeof(proxy->modalias));
	proxy->dev.platform_data = (void *) chip->platform_data;
	proxy->controller_data = chip->controller_data;
	proxy->controller_state = NULL;

	status = spi_add_device(proxy);
	if (status < 0) {
		spi_dev_put(proxy);
		return NULL;
	}

	return proxy;
}
EXPORT_SYMBOL_GPL(spi_new_device);

static void spi_match_master_to_boardinfo(struct spi_master *master,
				struct spi_board_info *bi)
{
	struct spi_device *dev;

	if (master->bus_num != bi->bus_num)
		return;

	dev = spi_new_device(master, bi);
	if (!dev)
		dev_err(master->dev.parent, "can't create new device for %s\n",
			bi->modalias);
}

/**
 * spi_register_board_info - register SPI devices for a given board
 * @info: array of chip descriptors
 * @n: how many descriptors are provided
 * Context: can sleep
 *
 * Board-specific early init code calls this (probably during arch_initcall)
 * with segments of the SPI device table.  Any device nodes are created later,
 * after the relevant parent SPI controller (bus_num) is defined.  We keep
 * this table of devices forever, so that reloading a controller driver will
 * not make Linux forget about these hard-wired devices.
 *
 * Other code can also call this, e.g. a particular add-on board might provide
 * SPI devices through its expansion connector, so code initializing that board
 * would naturally declare its SPI devices.
 *
 * The board info passed can safely be __initdata ... but be careful of
 * any embedded pointers (platform_data, etc), they're copied as-is.
 */
int __init
spi_register_board_info(struct spi_board_info const *info, unsigned n)
{
	struct boardinfo *bi;
	int i;

	bi = kzalloc(n * sizeof(*bi), GFP_KERNEL);
	if (!bi)
		return -ENOMEM;

	for (i = 0; i < n; i++, bi++, info++) {
		struct spi_master *master;

		memcpy(&bi->board_info, info, sizeof(*info));
		mutex_lock(&board_lock);
		list_add_tail(&bi->list, &board_list);
		list_for_each_entry(master, &spi_master_list, list)
			spi_match_master_to_boardinfo(master, &bi->board_info);
		mutex_unlock(&board_lock);
	}

	return 0;
}

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

static void spi_master_release(struct device *dev)
{
	struct spi_master *master;

	master = container_of(dev, struct spi_master, dev);
	kfree(master);
}

static struct class spi_master_class = {
	.name		= "spi_master",
	.owner		= THIS_MODULE,
	.dev_release	= spi_master_release,
};


/**
 * spi_alloc_master - allocate SPI master controller
 * @dev: the controller, possibly using the platform_bus
 * @size: how much zeroed driver-private data to allocate; the pointer to this
 *	memory is in the driver_data field of the returned device,
 *	accessible with spi_master_get_devdata().
 * Context: can sleep
 *
 * This call is used only by SPI master controller drivers, which are the
 * only ones directly touching chip registers.  It's how they allocate
 * an spi_master structure, prior to calling spi_register_master().
 *
 * This must be called from context that can sleep.  It returns the SPI
 * master structure on success, else NULL.
 *
 * The caller is responsible for assigning the bus number and initializing
 * the master's methods before calling spi_register_master(); and (after errors
 * adding the device) calling spi_master_put() to prevent a memory leak.
 */
struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
{
	struct spi_master	*master;

	if (!dev)
		return NULL;

	master = kzalloc(size + sizeof *master, GFP_KERNEL);
	if (!master)
		return NULL;

	device_initialize(&master->dev);
	master->dev.class = &spi_master_class;
	master->dev.parent = get_device(dev);
	spi_master_set_devdata(master, &master[1]);

	return master;
}
EXPORT_SYMBOL_GPL(spi_alloc_master);

/**
 * spi_register_master - register SPI master controller
 * @master: initialized master, originally from spi_alloc_master()
 * Context: can sleep
 *
 * SPI master controllers connect to their drivers using some non-SPI bus,
 * such as the platform bus.  The final stage of probe() in that code
 * includes calling spi_register_master() to hook up to this SPI bus glue.
 *
 * SPI controllers use board specific (often SOC specific) bus numbers,
 * and board-specific addressing for SPI devices combines those numbers
 * with chip select numbers.  Since SPI does not directly support dynamic
 * device identification, boards need configuration tables telling which
 * chip is at which address.
 *
 * This must be called from context that can sleep.  It returns zero on
 * success, else a negative error code (dropping the master's refcount).
 * After a successful return, the caller is responsible for calling
 * spi_unregister_master().
 */
int spi_register_master(struct spi_master *master)
{
	static atomic_t		dyn_bus_id = ATOMIC_INIT((1<<15) - 1);
	struct device		*dev = master->dev.parent;
	struct boardinfo	*bi;
	int			status = -ENODEV;
	int			dynamic = 0;

	if (!dev)
		return -ENODEV;

	/* even if it's just one always-selected device, there must
	 * be at least one chipselect
	 */
	if (master->num_chipselect == 0)
		return -EINVAL;

	/* convention:  dynamically assigned bus IDs count down from the max */
	if (master->bus_num < 0) {
		/* FIXME switch to an IDR based scheme, something like
		 * I2C now uses, so we can't run out of "dynamic" IDs
		 */
		master->bus_num = atomic_dec_return(&dyn_bus_id);
		dynamic = 1;
	}

	spin_lock_init(&master->bus_lock_spinlock);
	mutex_init(&master->bus_lock_mutex);
	master->bus_lock_flag = 0;

	/* register the device, then userspace will see it.
	 * registration fails if the bus ID is in use.
	 */
	dev_set_name(&master->dev, "spi%u", master->bus_num);
	status = device_add(&master->dev);
	if (status < 0)
		goto done;
	dev_dbg(dev, "registered master %s%s\n", dev_name(&master->dev),
			dynamic ? " (dynamic)" : "");

	mutex_lock(&board_lock);
	list_add_tail(&master->list, &spi_master_list);
	list_for_each_entry(bi, &board_list, list)
		spi_match_master_to_boardinfo(master, &bi->board_info);
	mutex_unlock(&board_lock);

	status = 0;

	/* Register devices from the device tree */
	of_register_spi_devices(master);
done:
	return status;
}
EXPORT_SYMBOL_GPL(spi_register_master);


static int __unregister(struct device *dev, void *null)
{
	spi_unregister_device(to_spi_device(dev));
	return 0;
}

/**
 * spi_unregister_master - unregister SPI master controller
 * @master: the master being unregistered
 * Context: can sleep
 *
 * This call is used only by SPI master controller drivers, which are the
 * only ones directly touching chip registers.
 *
 * This must be called from context that can sleep.
 */
void spi_unregister_master(struct spi_master *master)
{
	int dummy;

	mutex_lock(&board_lock);
	list_del(&master->list);
	mutex_unlock(&board_lock);

	dummy = device_for_each_child(&master->dev, NULL, __unregister);
	device_unregister(&master->dev);
}
EXPORT_SYMBOL_GPL(spi_unregister_master);

static int __spi_master_match(struct device *dev, void *data)
{
	struct spi_master *m;
	u16 *bus_num = data;

	m = container_of(dev, struct spi_master, dev);
	return m->bus_num == *bus_num;
}

/**
 * spi_busnum_to_master - look up master associated with bus_num
 * @bus_num: the master's bus number
 * Context: can sleep
 *
 * This call may be used with devices that are registered after
 * arch init time.  It returns a refcounted pointer to the relevant
 * spi_master (which the caller must release), or NULL if there is
 * no such master registered.
 */
struct spi_master *spi_busnum_to_master(u16 bus_num)
{
	struct device		*dev;
	struct spi_master	*master = NULL;

	dev = class_find_device(&spi_master_class, NULL, &bus_num,
				__spi_master_match);
	if (dev)
		master = container_of(dev, struct spi_master, dev);
	/* reference got in class_find_device */
	return master;
}
EXPORT_SYMBOL_GPL(spi_busnum_to_master);


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

/* Core methods for SPI master protocol drivers.  Some of the
 * other core methods are currently defined as inline functions.
 */

/**
 * spi_setup - setup SPI mode and clock rate
 * @spi: the device whose settings are being modified
 * Context: can sleep, and no requests are queued to the device
 *
 * SPI protocol drivers may need to update the transfer mode if the
 * device doesn't work with its default.  They may likewise need
 * to update clock rates or word sizes from initial values.  This function
 * changes those settings, and must be called from a context that can sleep.
 * Except for SPI_CS_HIGH, which takes effect immediately, the changes take
 * effect the next time the device is selected and data is transferred to
 * or from it.  When this function returns, the spi device is deselected.
 *
 * Note that this call will fail if the protocol driver specifies an option
 * that the underlying controller or its driver does not support.  For
 * example, not all hardware supports wire transfers using nine bit words,
 * LSB-first wire encoding, or active-high chipselects.
 */
int spi_setup(struct spi_device *spi)
{
	unsigned	bad_bits;
	int		status;

	/* help drivers fail *cleanly* when they need options
	 * that aren't supported with their current master
	 */
	bad_bits = spi->mode & ~spi->master->mode_bits;
	if (bad_bits) {
		dev_err(&spi->dev, "setup: unsupported mode bits %x\n",
			bad_bits);
		return -EINVAL;
	}

	if (!spi->bits_per_word)
		spi->bits_per_word = 8;

	status = spi->master->setup(spi);

	dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s"
				"%u bits/w, %u Hz max --> %d\n",
			(int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
			(spi->mode & SPI_CS_HIGH) ? "cs_high, " : "",
			(spi->mode & SPI_LSB_FIRST) ? "lsb, " : "",
			(spi->mode & SPI_3WIRE) ? "3wire, " : "",
			(spi->mode & SPI_LOOP) ? "loopback, " : "",
			spi->bits_per_word, spi->max_speed_hz,
			status);

	return status;
}
EXPORT_SYMBOL_GPL(spi_setup);

static int __spi_async(struct spi_device *spi, struct spi_message *message)
{
	struct spi_master *master = spi->master;

	/* Half-duplex links include original MicroWire, and ones with
	 * only one data pin like SPI_3WIRE (switches direction) or where
	 * either MOSI or MISO is missing.  They can also be caused by
	 * software limitations.
	 */
	if ((master->flags & SPI_MASTER_HALF_DUPLEX)
			|| (spi->mode & SPI_3WIRE)) {
		struct spi_transfer *xfer;
		unsigned flags = master->flags;

		list_for_each_entry(xfer, &message->transfers, transfer_list) {
			if (xfer->rx_buf && xfer->tx_buf)
				return -EINVAL;
			if ((flags & SPI_MASTER_NO_TX) && xfer->tx_buf)
				return -EINVAL;
			if ((flags & SPI_MASTER_NO_RX) && xfer->rx_buf)
				return -EINVAL;
		}
	}

	message->spi = spi;
	message->status = -EINPROGRESS;
	return master->transfer(spi, message);
}

/**
 * spi_async - asynchronous SPI transfer
 * @spi: device with which data will be exchanged
 * @message: describes the data transfers, including completion callback
 * Context: any (irqs may be blocked, etc)
 *
 * This call may be used in_irq and other contexts which can't sleep,
 * as well as from task contexts which can sleep.
 *
 * The completion callback is invoked in a context which can't sleep.
 * Before that invocation, the value of message->status is undefined.
 * When the callback is issued, message->status holds either zero (to
 * indicate complete success) or a negative error code.  After that
 * callback returns, the driver which issued the transfer request may
 * deallocate the associated memory; it's no longer in use by any SPI
 * core or controller driver code.
 *
 * Note that although all messages to a spi_device are handled in
 * FIFO order, messages may go to different devices in other orders.
 * Some device might be higher priority, or have various "hard" access
 * time requirements, for example.
 *
 * On detection of any fault during the transfer, processing of
 * the entire message is aborted, and the device is deselected.
 * Until returning from the associated message completion callback,
 * no other spi_message queued to that device will be processed.
 * (This rule applies equally to all the synchronous transfer calls,
 * which are wrappers around this core asynchronous primitive.)
 */
int spi_async(struct spi_device *spi, struct spi_message *message)
{
	struct spi_master *master = spi->master;
	int ret;
	unsigned long flags;

	spin_lock_irqsave(&master->bus_lock_spinlock, flags);

	if (master->bus_lock_flag)
		ret = -EBUSY;
	else
		ret = __spi_async(spi, message);

	spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);

	return ret;
}
EXPORT_SYMBOL_GPL(spi_async);

/**
 * spi_async_locked - version of spi_async with exclusive bus usage
 * @spi: device with which data will be exchanged
 * @message: describes the data transfers, including completion callback
 * Context: any (irqs may be blocked, etc)
 *
 * This call may be used in_irq and other contexts which can't sleep,
 * as well as from task contexts which can sleep.
 *
 * The completion callback is invoked in a context which can't sleep.
 * Before that invocation, the value of message->status is undefined.
 * When the callback is issued, message->status holds either zero (to
 * indicate complete success) or a negative error code.  After that
 * callback returns, the driver which issued the transfer request may
 * deallocate the associated memory; it's no longer in use by any SPI
 * core or controller driver code.
 *
 * Note that although all messages to a spi_device are handled in
 * FIFO order, messages may go to different devices in other orders.
 * Some device might be higher priority, or have various "hard" access
 * time requirements, for example.
 *
 * On detection of any fault during the transfer, processing of
 * the entire message is aborted, and the device is deselected.
 * Until returning from the associated message completion callback,
 * no other spi_message queued to that device will be processed.
 * (This rule applies equally to all the synchronous transfer calls,
 * which are wrappers around this core asynchronous primitive.)
 */
int spi_async_locked(struct spi_device *spi, struct spi_message *message)
{
	struct spi_master *master = spi->master;
	int ret;
	unsigned long flags;

	spin_lock_irqsave(&master->bus_lock_spinlock, flags);

	ret = __spi_async(spi, message);

	spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);

	return ret;

}
EXPORT_SYMBOL_GPL(spi_async_locked);


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

/* Utility methods for SPI master protocol drivers, layered on
 * top of the core.  Some other utility methods are defined as
 * inline functions.
 */

static void spi_complete(void *arg)
{
	complete(arg);
}

static int __spi_sync(struct spi_device *spi, struct spi_message *message,
		      int bus_locked)
{
	DECLARE_COMPLETION_ONSTACK(done);
	int status;
	struct spi_master *master = spi->master;

	message->complete = spi_complete;
	message->context = &done;

	if (!bus_locked)
		mutex_lock(&master->bus_lock_mutex);

	status = spi_async_locked(spi, message);

	if (!bus_locked)
		mutex_unlock(&master->bus_lock_mutex);

	if (status == 0) {
		wait_for_completion(&done);
		status = message->status;
	}
	message->context = NULL;
	return status;
}

/**
 * spi_sync - blocking/synchronous SPI data transfers
 * @spi: device with which data will be exchanged
 * @message: describes the data transfers
 * Context: can sleep
 *
 * This call may only be used from a context that may sleep.  The sleep
 * is non-interruptible, and has no timeout.  Low-overhead controller
 * drivers may DMA directly into and out of the message buffers.
 *
 * Note that the SPI device's chip select is active during the message,
 * and then is normally disabled between messages.  Drivers for some
 * frequently-used devices may want to minimize costs of selecting a chip,
 * by leaving it selected in anticipation that the next message will go
 * to the same chip.  (That may increase power usage.)
 *
 * Also, the caller is guaranteeing that the memory associated with the
 * message will not be freed before this call returns.
 *
 * It returns zero on success, else a negative error code.
 */
int spi_sync(struct spi_device *spi, struct spi_message *message)
{
	return __spi_sync(spi, message, 0);
}
EXPORT_SYMBOL_GPL(spi_sync);

/**
 * spi_sync_locked - version of spi_sync with exclusive bus usage
 * @spi: device with which data will be exchanged
 * @message: describes the data transfers
 * Context: can sleep
 *
 * This call may only be used from a context that may sleep.  The sleep
 * is non-interruptible, and has no timeout.  Low-overhead controller
 * drivers may DMA directly into and out of the message buffers.
 *
 * This call should be used by drivers that require exclusive access to the
 * SPI bus. It has to be preceeded by a spi_bus_lock call. The SPI bus must
 * be released by a spi_bus_unlock call when the exclusive access is over.
 *
 * It returns zero on success, else a negative error code.
 */
int spi_sync_locked(struct spi_device *spi, struct spi_message *message)
{
	return __spi_sync(spi, message, 1);
}
EXPORT_SYMBOL_GPL(spi_sync_locked);

/**
 * spi_bus_lock - obtain a lock for exclusive SPI bus usage
 * @master: SPI bus master that should be locked for exclusive bus access
 * Context: can sleep
 *
 * This call may only be used from a context that may sleep.  The sleep
 * is non-interruptible, and has no timeout.
 *
 * This call should be used by drivers that require exclusive access to the
 * SPI bus. The SPI bus must be released by a spi_bus_unlock call when the
 * exclusive access is over. Data transfer must be done by spi_sync_locked
 * and spi_async_locked calls when the SPI bus lock is held.
 *
 * It returns zero on success, else a negative error code.
 */
int spi_bus_lock(struct spi_master *master)
{
	unsigned long flags;

	mutex_lock(&master->bus_lock_mutex);

	spin_lock_irqsave(&master->bus_lock_spinlock, flags);
	master->bus_lock_flag = 1;
	spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);

	/* mutex remains locked until spi_bus_unlock is called */

	return 0;
}
EXPORT_SYMBOL_GPL(spi_bus_lock);

/**
 * spi_bus_unlock - release the lock for exclusive SPI bus usage
 * @master: SPI bus master that was locked for exclusive bus access
 * Context: can sleep
 *
 * This call may only be used from a context that may sleep.  The sleep
 * is non-interruptible, and has no timeout.
 *
 * This call releases an SPI bus lock previously obtained by an spi_bus_lock
 * call.
 *
 * It returns zero on success, else a negative error code.
 */
int spi_bus_unlock(struct spi_master *master)
{
	master->bus_lock_flag = 0;

	mutex_unlock(&master->bus_lock_mutex);

	return 0;
}
EXPORT_SYMBOL_GPL(spi_bus_unlock);

/* portable code must never pass more than 32 bytes */
#define	SPI_BUFSIZ	max(32,SMP_CACHE_BYTES)

static u8	*buf;

/**
 * spi_write_then_read - SPI synchronous write followed by read
 * @spi: device with which data will be exchanged
 * @txbuf: data to be written (need not be dma-safe)
 * @n_tx: size of txbuf, in bytes
 * @rxbuf: buffer into which data will be read (need not be dma-safe)
 * @n_rx: size of rxbuf, in bytes
 * Context: can sleep
 *
 * This performs a half duplex MicroWire style transaction with the
 * device, sending txbuf and then reading rxbuf.  The return value
 * is zero for success, else a negative errno status code.
 * This call may only be used from a context that may sleep.
 *
 * Parameters to this routine are always copied using a small buffer;
 * portable code should never use this for more than 32 bytes.
 * Performance-sensitive or bulk transfer code should instead use
 * spi_{async,sync}() calls with dma-safe buffers.
 */
int spi_write_then_read(struct spi_device *spi,
		const u8 *txbuf, unsigned n_tx,
		u8 *rxbuf, unsigned n_rx)
{
	static DEFINE_MUTEX(lock);

	int			status;
	struct spi_message	message;
	struct spi_transfer	x[2];
	u8			*local_buf;

	/* Use preallocated DMA-safe buffer.  We can't avoid copying here,
	 * (as a pure convenience thing), but we can keep heap costs
	 * out of the hot path ...
	 */
	if ((n_tx + n_rx) > SPI_BUFSIZ)
		return -EINVAL;

	spi_message_init(&message);
	memset(x, 0, sizeof x);
	if (n_tx) {
		x[0].len = n_tx;
		spi_message_add_tail(&x[0], &message);
	}
	if (n_rx) {
		x[1].len = n_rx;
		spi_message_add_tail(&x[1], &message);
	}

	/* ... unless someone else is using the pre-allocated buffer */
	if (!mutex_trylock(&lock)) {
		local_buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
		if (!local_buf)
			return -ENOMEM;
	} else
		local_buf = buf;

	memcpy(local_buf, txbuf, n_tx);
	x[0].tx_buf = local_buf;
	x[1].rx_buf = local_buf + n_tx;

	/* do the i/o */
	status = spi_sync(spi, &message);
	if (status == 0)
		memcpy(rxbuf, x[1].rx_buf, n_rx);

	if (x[0].tx_buf == buf)
		mutex_unlock(&lock);
	else
		kfree(local_buf);

	return status;
}
EXPORT_SYMBOL_GPL(spi_write_then_read);

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

static int __init spi_init(void)
{
	int	status;

	buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
	if (!buf) {
		status = -ENOMEM;
		goto err0;
	}

	status = bus_register(&spi_bus_type);
	if (status < 0)
		goto err1;

	status = class_register(&spi_master_class);
	if (status < 0)
		goto err2;
	return 0;

err2:
	bus_unregister(&spi_bus_type);
err1:
	kfree(buf);
	buf = NULL;
err0:
	return status;
}

/* board_info is normally registered in arch_initcall(),
 * but even essential drivers wait till later
 *
 * REVISIT only boardinfo really needs static linking. the rest (device and
 * driver registration) _could_ be dynamically linked (modular) ... costs
 * include needing to have boardinfo data structures be much more public.
 */
postcore_initcall(spi_init);