summaryrefslogtreecommitdiff
path: root/drivers/iio/industrialio-buffer.c
blob: 176d31d9f9d807ed2b8d83ab706c085cf2e56590 (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
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
// SPDX-License-Identifier: GPL-2.0-only
/* The industrial I/O core
 *
 * Copyright (c) 2008 Jonathan Cameron
 *
 * Handling of buffer allocation / resizing.
 *
 * Things to look at here.
 * - Better memory allocation techniques?
 * - Alternative access techniques?
 */
#include <linux/anon_inodes.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/device.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/sched/signal.h>

#include <linux/iio/iio.h>
#include <linux/iio/iio-opaque.h>
#include "iio_core.h"
#include "iio_core_trigger.h"
#include <linux/iio/sysfs.h>
#include <linux/iio/buffer.h>
#include <linux/iio/buffer_impl.h>

static const char * const iio_endian_prefix[] = {
	[IIO_BE] = "be",
	[IIO_LE] = "le",
};

static bool iio_buffer_is_active(struct iio_buffer *buf)
{
	return !list_empty(&buf->buffer_list);
}

static size_t iio_buffer_data_available(struct iio_buffer *buf)
{
	return buf->access->data_available(buf);
}

static int iio_buffer_flush_hwfifo(struct iio_dev *indio_dev,
				   struct iio_buffer *buf, size_t required)
{
	if (!indio_dev->info->hwfifo_flush_to_buffer)
		return -ENODEV;

	return indio_dev->info->hwfifo_flush_to_buffer(indio_dev, required);
}

static bool iio_buffer_ready(struct iio_dev *indio_dev, struct iio_buffer *buf,
			     size_t to_wait, int to_flush)
{
	size_t avail;
	int flushed = 0;

	/* wakeup if the device was unregistered */
	if (!indio_dev->info)
		return true;

	/* drain the buffer if it was disabled */
	if (!iio_buffer_is_active(buf)) {
		to_wait = min_t(size_t, to_wait, 1);
		to_flush = 0;
	}

	avail = iio_buffer_data_available(buf);

	if (avail >= to_wait) {
		/* force a flush for non-blocking reads */
		if (!to_wait && avail < to_flush)
			iio_buffer_flush_hwfifo(indio_dev, buf,
						to_flush - avail);
		return true;
	}

	if (to_flush)
		flushed = iio_buffer_flush_hwfifo(indio_dev, buf,
						  to_wait - avail);
	if (flushed <= 0)
		return false;

	if (avail + flushed >= to_wait)
		return true;

	return false;
}

/**
 * iio_buffer_read() - chrdev read for buffer access
 * @filp:	File structure pointer for the char device
 * @buf:	Destination buffer for iio buffer read
 * @n:		First n bytes to read
 * @f_ps:	Long offset provided by the user as a seek position
 *
 * This function relies on all buffer implementations having an
 * iio_buffer as their first element.
 *
 * Return: negative values corresponding to error codes or ret != 0
 *	   for ending the reading activity
 **/
static ssize_t iio_buffer_read(struct file *filp, char __user *buf,
			       size_t n, loff_t *f_ps)
{
	struct iio_dev_buffer_pair *ib = filp->private_data;
	struct iio_buffer *rb = ib->buffer;
	struct iio_dev *indio_dev = ib->indio_dev;
	DEFINE_WAIT_FUNC(wait, woken_wake_function);
	size_t datum_size;
	size_t to_wait;
	int ret = 0;

	if (!indio_dev->info)
		return -ENODEV;

	if (!rb || !rb->access->read)
		return -EINVAL;

	if (rb->direction != IIO_BUFFER_DIRECTION_IN)
		return -EPERM;

	datum_size = rb->bytes_per_datum;

	/*
	 * If datum_size is 0 there will never be anything to read from the
	 * buffer, so signal end of file now.
	 */
	if (!datum_size)
		return 0;

	if (filp->f_flags & O_NONBLOCK)
		to_wait = 0;
	else
		to_wait = min_t(size_t, n / datum_size, rb->watermark);

	add_wait_queue(&rb->pollq, &wait);
	do {
		if (!indio_dev->info) {
			ret = -ENODEV;
			break;
		}

		if (!iio_buffer_ready(indio_dev, rb, to_wait, n / datum_size)) {
			if (signal_pending(current)) {
				ret = -ERESTARTSYS;
				break;
			}

			wait_woken(&wait, TASK_INTERRUPTIBLE,
				   MAX_SCHEDULE_TIMEOUT);
			continue;
		}

		ret = rb->access->read(rb, n, buf);
		if (ret == 0 && (filp->f_flags & O_NONBLOCK))
			ret = -EAGAIN;
	} while (ret == 0);
	remove_wait_queue(&rb->pollq, &wait);

	return ret;
}

static size_t iio_buffer_space_available(struct iio_buffer *buf)
{
	if (buf->access->space_available)
		return buf->access->space_available(buf);

	return SIZE_MAX;
}

static ssize_t iio_buffer_write(struct file *filp, const char __user *buf,
				size_t n, loff_t *f_ps)
{
	struct iio_dev_buffer_pair *ib = filp->private_data;
	struct iio_buffer *rb = ib->buffer;
	struct iio_dev *indio_dev = ib->indio_dev;
	DEFINE_WAIT_FUNC(wait, woken_wake_function);
	int ret = 0;
	size_t written;

	if (!indio_dev->info)
		return -ENODEV;

	if (!rb || !rb->access->write)
		return -EINVAL;

	if (rb->direction != IIO_BUFFER_DIRECTION_OUT)
		return -EPERM;

	written = 0;
	add_wait_queue(&rb->pollq, &wait);
	do {
		if (!indio_dev->info)
			return -ENODEV;

		if (!iio_buffer_space_available(rb)) {
			if (signal_pending(current)) {
				ret = -ERESTARTSYS;
				break;
			}

			if (filp->f_flags & O_NONBLOCK) {
				if (!written)
					ret = -EAGAIN;
				break;
			}

			wait_woken(&wait, TASK_INTERRUPTIBLE,
				   MAX_SCHEDULE_TIMEOUT);
			continue;
		}

		ret = rb->access->write(rb, n - written, buf + written);
		if (ret < 0)
			break;

		written += ret;

	} while (written != n);
	remove_wait_queue(&rb->pollq, &wait);

	return ret < 0 ? ret : written;
}

/**
 * iio_buffer_poll() - poll the buffer to find out if it has data
 * @filp:	File structure pointer for device access
 * @wait:	Poll table structure pointer for which the driver adds
 *		a wait queue
 *
 * Return: (EPOLLIN | EPOLLRDNORM) if data is available for reading
 *	   or 0 for other cases
 */
static __poll_t iio_buffer_poll(struct file *filp,
				struct poll_table_struct *wait)
{
	struct iio_dev_buffer_pair *ib = filp->private_data;
	struct iio_buffer *rb = ib->buffer;
	struct iio_dev *indio_dev = ib->indio_dev;

	if (!indio_dev->info || !rb)
		return 0;

	poll_wait(filp, &rb->pollq, wait);

	switch (rb->direction) {
	case IIO_BUFFER_DIRECTION_IN:
		if (iio_buffer_ready(indio_dev, rb, rb->watermark, 0))
			return EPOLLIN | EPOLLRDNORM;
		break;
	case IIO_BUFFER_DIRECTION_OUT:
		if (iio_buffer_space_available(rb))
			return EPOLLOUT | EPOLLWRNORM;
		break;
	}

	return 0;
}

ssize_t iio_buffer_read_wrapper(struct file *filp, char __user *buf,
				size_t n, loff_t *f_ps)
{
	struct iio_dev_buffer_pair *ib = filp->private_data;
	struct iio_buffer *rb = ib->buffer;

	/* check if buffer was opened through new API */
	if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
		return -EBUSY;

	return iio_buffer_read(filp, buf, n, f_ps);
}

ssize_t iio_buffer_write_wrapper(struct file *filp, const char __user *buf,
				 size_t n, loff_t *f_ps)
{
	struct iio_dev_buffer_pair *ib = filp->private_data;
	struct iio_buffer *rb = ib->buffer;

	/* check if buffer was opened through new API */
	if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
		return -EBUSY;

	return iio_buffer_write(filp, buf, n, f_ps);
}

__poll_t iio_buffer_poll_wrapper(struct file *filp,
				 struct poll_table_struct *wait)
{
	struct iio_dev_buffer_pair *ib = filp->private_data;
	struct iio_buffer *rb = ib->buffer;

	/* check if buffer was opened through new API */
	if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
		return 0;

	return iio_buffer_poll(filp, wait);
}

/**
 * iio_buffer_wakeup_poll - Wakes up the buffer waitqueue
 * @indio_dev: The IIO device
 *
 * Wakes up the event waitqueue used for poll(). Should usually
 * be called when the device is unregistered.
 */
void iio_buffer_wakeup_poll(struct iio_dev *indio_dev)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer *buffer;
	unsigned int i;

	for (i = 0; i < iio_dev_opaque->attached_buffers_cnt; i++) {
		buffer = iio_dev_opaque->attached_buffers[i];
		wake_up(&buffer->pollq);
	}
}

int iio_pop_from_buffer(struct iio_buffer *buffer, void *data)
{
	if (!buffer || !buffer->access || !buffer->access->remove_from)
		return -EINVAL;

	return buffer->access->remove_from(buffer, data);
}
EXPORT_SYMBOL_GPL(iio_pop_from_buffer);

void iio_buffer_init(struct iio_buffer *buffer)
{
	INIT_LIST_HEAD(&buffer->demux_list);
	INIT_LIST_HEAD(&buffer->buffer_list);
	init_waitqueue_head(&buffer->pollq);
	kref_init(&buffer->ref);
	if (!buffer->watermark)
		buffer->watermark = 1;
}
EXPORT_SYMBOL(iio_buffer_init);

void iio_device_detach_buffers(struct iio_dev *indio_dev)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer *buffer;
	unsigned int i;

	for (i = 0; i < iio_dev_opaque->attached_buffers_cnt; i++) {
		buffer = iio_dev_opaque->attached_buffers[i];
		iio_buffer_put(buffer);
	}

	kfree(iio_dev_opaque->attached_buffers);
}

static ssize_t iio_show_scan_index(struct device *dev,
				   struct device_attribute *attr,
				   char *buf)
{
	return sysfs_emit(buf, "%u\n", to_iio_dev_attr(attr)->c->scan_index);
}

static ssize_t iio_show_fixed_type(struct device *dev,
				   struct device_attribute *attr,
				   char *buf)
{
	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
	u8 type = this_attr->c->scan_type.endianness;

	if (type == IIO_CPU) {
#ifdef __LITTLE_ENDIAN
		type = IIO_LE;
#else
		type = IIO_BE;
#endif
	}
	if (this_attr->c->scan_type.repeat > 1)
		return sysfs_emit(buf, "%s:%c%d/%dX%d>>%u\n",
		       iio_endian_prefix[type],
		       this_attr->c->scan_type.sign,
		       this_attr->c->scan_type.realbits,
		       this_attr->c->scan_type.storagebits,
		       this_attr->c->scan_type.repeat,
		       this_attr->c->scan_type.shift);
	else
		return sysfs_emit(buf, "%s:%c%d/%d>>%u\n",
		       iio_endian_prefix[type],
		       this_attr->c->scan_type.sign,
		       this_attr->c->scan_type.realbits,
		       this_attr->c->scan_type.storagebits,
		       this_attr->c->scan_type.shift);
}

static ssize_t iio_scan_el_show(struct device *dev,
				struct device_attribute *attr,
				char *buf)
{
	int ret;
	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

	/* Ensure ret is 0 or 1. */
	ret = !!test_bit(to_iio_dev_attr(attr)->address,
		       buffer->scan_mask);

	return sysfs_emit(buf, "%d\n", ret);
}

/* Note NULL used as error indicator as it doesn't make sense. */
static const unsigned long *iio_scan_mask_match(const unsigned long *av_masks,
						unsigned int masklength,
						const unsigned long *mask,
						bool strict)
{
	if (bitmap_empty(mask, masklength))
		return NULL;
	while (*av_masks) {
		if (strict) {
			if (bitmap_equal(mask, av_masks, masklength))
				return av_masks;
		} else {
			if (bitmap_subset(mask, av_masks, masklength))
				return av_masks;
		}
		av_masks += BITS_TO_LONGS(masklength);
	}
	return NULL;
}

static bool iio_validate_scan_mask(struct iio_dev *indio_dev,
				   const unsigned long *mask)
{
	if (!indio_dev->setup_ops->validate_scan_mask)
		return true;

	return indio_dev->setup_ops->validate_scan_mask(indio_dev, mask);
}

/**
 * iio_scan_mask_set() - set particular bit in the scan mask
 * @indio_dev: the iio device
 * @buffer: the buffer whose scan mask we are interested in
 * @bit: the bit to be set.
 *
 * Note that at this point we have no way of knowing what other
 * buffers might request, hence this code only verifies that the
 * individual buffers request is plausible.
 */
static int iio_scan_mask_set(struct iio_dev *indio_dev,
			     struct iio_buffer *buffer, int bit)
{
	const unsigned long *mask;
	unsigned long *trialmask;

	if (!indio_dev->masklength) {
		WARN(1, "Trying to set scanmask prior to registering buffer\n");
		return -EINVAL;
	}

	trialmask = bitmap_alloc(indio_dev->masklength, GFP_KERNEL);
	if (!trialmask)
		return -ENOMEM;
	bitmap_copy(trialmask, buffer->scan_mask, indio_dev->masklength);
	set_bit(bit, trialmask);

	if (!iio_validate_scan_mask(indio_dev, trialmask))
		goto err_invalid_mask;

	if (indio_dev->available_scan_masks) {
		mask = iio_scan_mask_match(indio_dev->available_scan_masks,
					   indio_dev->masklength,
					   trialmask, false);
		if (!mask)
			goto err_invalid_mask;
	}
	bitmap_copy(buffer->scan_mask, trialmask, indio_dev->masklength);

	bitmap_free(trialmask);

	return 0;

err_invalid_mask:
	bitmap_free(trialmask);
	return -EINVAL;
}

static int iio_scan_mask_clear(struct iio_buffer *buffer, int bit)
{
	clear_bit(bit, buffer->scan_mask);
	return 0;
}

static int iio_scan_mask_query(struct iio_dev *indio_dev,
			       struct iio_buffer *buffer, int bit)
{
	if (bit > indio_dev->masklength)
		return -EINVAL;

	if (!buffer->scan_mask)
		return 0;

	/* Ensure return value is 0 or 1. */
	return !!test_bit(bit, buffer->scan_mask);
};

static ssize_t iio_scan_el_store(struct device *dev,
				 struct device_attribute *attr,
				 const char *buf,
				 size_t len)
{
	int ret;
	bool state;
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
	struct iio_buffer *buffer = this_attr->buffer;

	ret = kstrtobool(buf, &state);
	if (ret < 0)
		return ret;
	mutex_lock(&iio_dev_opaque->mlock);
	if (iio_buffer_is_active(buffer)) {
		ret = -EBUSY;
		goto error_ret;
	}
	ret = iio_scan_mask_query(indio_dev, buffer, this_attr->address);
	if (ret < 0)
		goto error_ret;
	if (!state && ret) {
		ret = iio_scan_mask_clear(buffer, this_attr->address);
		if (ret)
			goto error_ret;
	} else if (state && !ret) {
		ret = iio_scan_mask_set(indio_dev, buffer, this_attr->address);
		if (ret)
			goto error_ret;
	}

error_ret:
	mutex_unlock(&iio_dev_opaque->mlock);

	return ret < 0 ? ret : len;
}

static ssize_t iio_scan_el_ts_show(struct device *dev,
				   struct device_attribute *attr,
				   char *buf)
{
	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

	return sysfs_emit(buf, "%d\n", buffer->scan_timestamp);
}

static ssize_t iio_scan_el_ts_store(struct device *dev,
				    struct device_attribute *attr,
				    const char *buf,
				    size_t len)
{
	int ret;
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
	bool state;

	ret = kstrtobool(buf, &state);
	if (ret < 0)
		return ret;

	mutex_lock(&iio_dev_opaque->mlock);
	if (iio_buffer_is_active(buffer)) {
		ret = -EBUSY;
		goto error_ret;
	}
	buffer->scan_timestamp = state;
error_ret:
	mutex_unlock(&iio_dev_opaque->mlock);

	return ret ? ret : len;
}

static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
					struct iio_buffer *buffer,
					const struct iio_chan_spec *chan)
{
	int ret, attrcount = 0;

	ret = __iio_add_chan_devattr("index",
				     chan,
				     &iio_show_scan_index,
				     NULL,
				     0,
				     IIO_SEPARATE,
				     &indio_dev->dev,
				     buffer,
				     &buffer->buffer_attr_list);
	if (ret)
		return ret;
	attrcount++;
	ret = __iio_add_chan_devattr("type",
				     chan,
				     &iio_show_fixed_type,
				     NULL,
				     0,
				     0,
				     &indio_dev->dev,
				     buffer,
				     &buffer->buffer_attr_list);
	if (ret)
		return ret;
	attrcount++;
	if (chan->type != IIO_TIMESTAMP)
		ret = __iio_add_chan_devattr("en",
					     chan,
					     &iio_scan_el_show,
					     &iio_scan_el_store,
					     chan->scan_index,
					     0,
					     &indio_dev->dev,
					     buffer,
					     &buffer->buffer_attr_list);
	else
		ret = __iio_add_chan_devattr("en",
					     chan,
					     &iio_scan_el_ts_show,
					     &iio_scan_el_ts_store,
					     chan->scan_index,
					     0,
					     &indio_dev->dev,
					     buffer,
					     &buffer->buffer_attr_list);
	if (ret)
		return ret;
	attrcount++;
	ret = attrcount;
	return ret;
}

static ssize_t length_show(struct device *dev, struct device_attribute *attr,
			   char *buf)
{
	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

	return sysfs_emit(buf, "%d\n", buffer->length);
}

static ssize_t length_store(struct device *dev, struct device_attribute *attr,
			    const char *buf, size_t len)
{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
	unsigned int val;
	int ret;

	ret = kstrtouint(buf, 10, &val);
	if (ret)
		return ret;

	if (val == buffer->length)
		return len;

	mutex_lock(&iio_dev_opaque->mlock);
	if (iio_buffer_is_active(buffer)) {
		ret = -EBUSY;
	} else {
		buffer->access->set_length(buffer, val);
		ret = 0;
	}
	if (ret)
		goto out;
	if (buffer->length && buffer->length < buffer->watermark)
		buffer->watermark = buffer->length;
out:
	mutex_unlock(&iio_dev_opaque->mlock);

	return ret ? ret : len;
}

static ssize_t enable_show(struct device *dev, struct device_attribute *attr,
			   char *buf)
{
	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

	return sysfs_emit(buf, "%d\n", iio_buffer_is_active(buffer));
}

static unsigned int iio_storage_bytes_for_si(struct iio_dev *indio_dev,
					     unsigned int scan_index)
{
	const struct iio_chan_spec *ch;
	unsigned int bytes;

	ch = iio_find_channel_from_si(indio_dev, scan_index);
	bytes = ch->scan_type.storagebits / 8;
	if (ch->scan_type.repeat > 1)
		bytes *= ch->scan_type.repeat;
	return bytes;
}

static unsigned int iio_storage_bytes_for_timestamp(struct iio_dev *indio_dev)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);

	return iio_storage_bytes_for_si(indio_dev,
					iio_dev_opaque->scan_index_timestamp);
}

static int iio_compute_scan_bytes(struct iio_dev *indio_dev,
				  const unsigned long *mask, bool timestamp)
{
	unsigned int bytes = 0;
	int length, i, largest = 0;

	/* How much space will the demuxed element take? */
	for_each_set_bit(i, mask,
			 indio_dev->masklength) {
		length = iio_storage_bytes_for_si(indio_dev, i);
		bytes = ALIGN(bytes, length);
		bytes += length;
		largest = max(largest, length);
	}

	if (timestamp) {
		length = iio_storage_bytes_for_timestamp(indio_dev);
		bytes = ALIGN(bytes, length);
		bytes += length;
		largest = max(largest, length);
	}

	bytes = ALIGN(bytes, largest);
	return bytes;
}

static void iio_buffer_activate(struct iio_dev *indio_dev,
				struct iio_buffer *buffer)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);

	iio_buffer_get(buffer);
	list_add(&buffer->buffer_list, &iio_dev_opaque->buffer_list);
}

static void iio_buffer_deactivate(struct iio_buffer *buffer)
{
	list_del_init(&buffer->buffer_list);
	wake_up_interruptible(&buffer->pollq);
	iio_buffer_put(buffer);
}

static void iio_buffer_deactivate_all(struct iio_dev *indio_dev)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer *buffer, *_buffer;

	list_for_each_entry_safe(buffer, _buffer,
				 &iio_dev_opaque->buffer_list, buffer_list)
		iio_buffer_deactivate(buffer);
}

static int iio_buffer_enable(struct iio_buffer *buffer,
			     struct iio_dev *indio_dev)
{
	if (!buffer->access->enable)
		return 0;
	return buffer->access->enable(buffer, indio_dev);
}

static int iio_buffer_disable(struct iio_buffer *buffer,
			      struct iio_dev *indio_dev)
{
	if (!buffer->access->disable)
		return 0;
	return buffer->access->disable(buffer, indio_dev);
}

static void iio_buffer_update_bytes_per_datum(struct iio_dev *indio_dev,
					      struct iio_buffer *buffer)
{
	unsigned int bytes;

	if (!buffer->access->set_bytes_per_datum)
		return;

	bytes = iio_compute_scan_bytes(indio_dev, buffer->scan_mask,
				       buffer->scan_timestamp);

	buffer->access->set_bytes_per_datum(buffer, bytes);
}

static int iio_buffer_request_update(struct iio_dev *indio_dev,
				     struct iio_buffer *buffer)
{
	int ret;

	iio_buffer_update_bytes_per_datum(indio_dev, buffer);
	if (buffer->access->request_update) {
		ret = buffer->access->request_update(buffer);
		if (ret) {
			dev_dbg(&indio_dev->dev,
				"Buffer not started: buffer parameter update failed (%d)\n",
				ret);
			return ret;
		}
	}

	return 0;
}

static void iio_free_scan_mask(struct iio_dev *indio_dev,
			       const unsigned long *mask)
{
	/* If the mask is dynamically allocated free it, otherwise do nothing */
	if (!indio_dev->available_scan_masks)
		bitmap_free(mask);
}

struct iio_device_config {
	unsigned int mode;
	unsigned int watermark;
	const unsigned long *scan_mask;
	unsigned int scan_bytes;
	bool scan_timestamp;
};

static int iio_verify_update(struct iio_dev *indio_dev,
			     struct iio_buffer *insert_buffer,
			     struct iio_buffer *remove_buffer,
			     struct iio_device_config *config)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	unsigned long *compound_mask;
	const unsigned long *scan_mask;
	bool strict_scanmask = false;
	struct iio_buffer *buffer;
	bool scan_timestamp;
	unsigned int modes;

	if (insert_buffer &&
	    bitmap_empty(insert_buffer->scan_mask, indio_dev->masklength)) {
		dev_dbg(&indio_dev->dev,
			"At least one scan element must be enabled first\n");
		return -EINVAL;
	}

	memset(config, 0, sizeof(*config));
	config->watermark = ~0;

	/*
	 * If there is just one buffer and we are removing it there is nothing
	 * to verify.
	 */
	if (remove_buffer && !insert_buffer &&
	    list_is_singular(&iio_dev_opaque->buffer_list))
		return 0;

	modes = indio_dev->modes;

	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
		if (buffer == remove_buffer)
			continue;
		modes &= buffer->access->modes;
		config->watermark = min(config->watermark, buffer->watermark);
	}

	if (insert_buffer) {
		modes &= insert_buffer->access->modes;
		config->watermark = min(config->watermark,
					insert_buffer->watermark);
	}

	/* Definitely possible for devices to support both of these. */
	if ((modes & INDIO_BUFFER_TRIGGERED) && indio_dev->trig) {
		config->mode = INDIO_BUFFER_TRIGGERED;
	} else if (modes & INDIO_BUFFER_HARDWARE) {
		/*
		 * Keep things simple for now and only allow a single buffer to
		 * be connected in hardware mode.
		 */
		if (insert_buffer && !list_empty(&iio_dev_opaque->buffer_list))
			return -EINVAL;
		config->mode = INDIO_BUFFER_HARDWARE;
		strict_scanmask = true;
	} else if (modes & INDIO_BUFFER_SOFTWARE) {
		config->mode = INDIO_BUFFER_SOFTWARE;
	} else {
		/* Can only occur on first buffer */
		if (indio_dev->modes & INDIO_BUFFER_TRIGGERED)
			dev_dbg(&indio_dev->dev, "Buffer not started: no trigger\n");
		return -EINVAL;
	}

	/* What scan mask do we actually have? */
	compound_mask = bitmap_zalloc(indio_dev->masklength, GFP_KERNEL);
	if (!compound_mask)
		return -ENOMEM;

	scan_timestamp = false;

	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
		if (buffer == remove_buffer)
			continue;
		bitmap_or(compound_mask, compound_mask, buffer->scan_mask,
			  indio_dev->masklength);
		scan_timestamp |= buffer->scan_timestamp;
	}

	if (insert_buffer) {
		bitmap_or(compound_mask, compound_mask,
			  insert_buffer->scan_mask, indio_dev->masklength);
		scan_timestamp |= insert_buffer->scan_timestamp;
	}

	if (indio_dev->available_scan_masks) {
		scan_mask = iio_scan_mask_match(indio_dev->available_scan_masks,
						indio_dev->masklength,
						compound_mask,
						strict_scanmask);
		bitmap_free(compound_mask);
		if (!scan_mask)
			return -EINVAL;
	} else {
		scan_mask = compound_mask;
	}

	config->scan_bytes = iio_compute_scan_bytes(indio_dev,
						    scan_mask, scan_timestamp);
	config->scan_mask = scan_mask;
	config->scan_timestamp = scan_timestamp;

	return 0;
}

/**
 * struct iio_demux_table - table describing demux memcpy ops
 * @from:	index to copy from
 * @to:		index to copy to
 * @length:	how many bytes to copy
 * @l:		list head used for management
 */
struct iio_demux_table {
	unsigned int from;
	unsigned int to;
	unsigned int length;
	struct list_head l;
};

static void iio_buffer_demux_free(struct iio_buffer *buffer)
{
	struct iio_demux_table *p, *q;

	list_for_each_entry_safe(p, q, &buffer->demux_list, l) {
		list_del(&p->l);
		kfree(p);
	}
}

static int iio_buffer_add_demux(struct iio_buffer *buffer,
				struct iio_demux_table **p, unsigned int in_loc,
				unsigned int out_loc,
				unsigned int length)
{
	if (*p && (*p)->from + (*p)->length == in_loc &&
	    (*p)->to + (*p)->length == out_loc) {
		(*p)->length += length;
	} else {
		*p = kmalloc(sizeof(**p), GFP_KERNEL);
		if (!(*p))
			return -ENOMEM;
		(*p)->from = in_loc;
		(*p)->to = out_loc;
		(*p)->length = length;
		list_add_tail(&(*p)->l, &buffer->demux_list);
	}

	return 0;
}

static int iio_buffer_update_demux(struct iio_dev *indio_dev,
				   struct iio_buffer *buffer)
{
	int ret, in_ind = -1, out_ind, length;
	unsigned int in_loc = 0, out_loc = 0;
	struct iio_demux_table *p = NULL;

	/* Clear out any old demux */
	iio_buffer_demux_free(buffer);
	kfree(buffer->demux_bounce);
	buffer->demux_bounce = NULL;

	/* First work out which scan mode we will actually have */
	if (bitmap_equal(indio_dev->active_scan_mask,
			 buffer->scan_mask,
			 indio_dev->masklength))
		return 0;

	/* Now we have the two masks, work from least sig and build up sizes */
	for_each_set_bit(out_ind,
			 buffer->scan_mask,
			 indio_dev->masklength) {
		in_ind = find_next_bit(indio_dev->active_scan_mask,
				       indio_dev->masklength,
				       in_ind + 1);
		while (in_ind != out_ind) {
			length = iio_storage_bytes_for_si(indio_dev, in_ind);
			/* Make sure we are aligned */
			in_loc = roundup(in_loc, length) + length;
			in_ind = find_next_bit(indio_dev->active_scan_mask,
					       indio_dev->masklength,
					       in_ind + 1);
		}
		length = iio_storage_bytes_for_si(indio_dev, in_ind);
		out_loc = roundup(out_loc, length);
		in_loc = roundup(in_loc, length);
		ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
		if (ret)
			goto error_clear_mux_table;
		out_loc += length;
		in_loc += length;
	}
	/* Relies on scan_timestamp being last */
	if (buffer->scan_timestamp) {
		length = iio_storage_bytes_for_timestamp(indio_dev);
		out_loc = roundup(out_loc, length);
		in_loc = roundup(in_loc, length);
		ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
		if (ret)
			goto error_clear_mux_table;
		out_loc += length;
	}
	buffer->demux_bounce = kzalloc(out_loc, GFP_KERNEL);
	if (!buffer->demux_bounce) {
		ret = -ENOMEM;
		goto error_clear_mux_table;
	}
	return 0;

error_clear_mux_table:
	iio_buffer_demux_free(buffer);

	return ret;
}

static int iio_update_demux(struct iio_dev *indio_dev)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer *buffer;
	int ret;

	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
		ret = iio_buffer_update_demux(indio_dev, buffer);
		if (ret < 0)
			goto error_clear_mux_table;
	}
	return 0;

error_clear_mux_table:
	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list)
		iio_buffer_demux_free(buffer);

	return ret;
}

static int iio_enable_buffers(struct iio_dev *indio_dev,
			      struct iio_device_config *config)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer *buffer, *tmp = NULL;
	int ret;

	indio_dev->active_scan_mask = config->scan_mask;
	indio_dev->scan_timestamp = config->scan_timestamp;
	indio_dev->scan_bytes = config->scan_bytes;
	iio_dev_opaque->currentmode = config->mode;

	iio_update_demux(indio_dev);

	/* Wind up again */
	if (indio_dev->setup_ops->preenable) {
		ret = indio_dev->setup_ops->preenable(indio_dev);
		if (ret) {
			dev_dbg(&indio_dev->dev,
				"Buffer not started: buffer preenable failed (%d)\n", ret);
			goto err_undo_config;
		}
	}

	if (indio_dev->info->update_scan_mode) {
		ret = indio_dev->info
			->update_scan_mode(indio_dev,
					   indio_dev->active_scan_mask);
		if (ret < 0) {
			dev_dbg(&indio_dev->dev,
				"Buffer not started: update scan mode failed (%d)\n",
				ret);
			goto err_run_postdisable;
		}
	}

	if (indio_dev->info->hwfifo_set_watermark)
		indio_dev->info->hwfifo_set_watermark(indio_dev,
			config->watermark);

	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
		ret = iio_buffer_enable(buffer, indio_dev);
		if (ret) {
			tmp = buffer;
			goto err_disable_buffers;
		}
	}

	if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
		ret = iio_trigger_attach_poll_func(indio_dev->trig,
						   indio_dev->pollfunc);
		if (ret)
			goto err_disable_buffers;
	}

	if (indio_dev->setup_ops->postenable) {
		ret = indio_dev->setup_ops->postenable(indio_dev);
		if (ret) {
			dev_dbg(&indio_dev->dev,
				"Buffer not started: postenable failed (%d)\n", ret);
			goto err_detach_pollfunc;
		}
	}

	return 0;

err_detach_pollfunc:
	if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
		iio_trigger_detach_poll_func(indio_dev->trig,
					     indio_dev->pollfunc);
	}
err_disable_buffers:
	buffer = list_prepare_entry(tmp, &iio_dev_opaque->buffer_list, buffer_list);
	list_for_each_entry_continue_reverse(buffer, &iio_dev_opaque->buffer_list,
					     buffer_list)
		iio_buffer_disable(buffer, indio_dev);
err_run_postdisable:
	if (indio_dev->setup_ops->postdisable)
		indio_dev->setup_ops->postdisable(indio_dev);
err_undo_config:
	iio_dev_opaque->currentmode = INDIO_DIRECT_MODE;
	indio_dev->active_scan_mask = NULL;

	return ret;
}

static int iio_disable_buffers(struct iio_dev *indio_dev)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer *buffer;
	int ret = 0;
	int ret2;

	/* Wind down existing buffers - iff there are any */
	if (list_empty(&iio_dev_opaque->buffer_list))
		return 0;

	/*
	 * If things go wrong at some step in disable we still need to continue
	 * to perform the other steps, otherwise we leave the device in a
	 * inconsistent state. We return the error code for the first error we
	 * encountered.
	 */

	if (indio_dev->setup_ops->predisable) {
		ret2 = indio_dev->setup_ops->predisable(indio_dev);
		if (ret2 && !ret)
			ret = ret2;
	}

	if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
		iio_trigger_detach_poll_func(indio_dev->trig,
					     indio_dev->pollfunc);
	}

	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
		ret2 = iio_buffer_disable(buffer, indio_dev);
		if (ret2 && !ret)
			ret = ret2;
	}

	if (indio_dev->setup_ops->postdisable) {
		ret2 = indio_dev->setup_ops->postdisable(indio_dev);
		if (ret2 && !ret)
			ret = ret2;
	}

	iio_free_scan_mask(indio_dev, indio_dev->active_scan_mask);
	indio_dev->active_scan_mask = NULL;
	iio_dev_opaque->currentmode = INDIO_DIRECT_MODE;

	return ret;
}

static int __iio_update_buffers(struct iio_dev *indio_dev,
				struct iio_buffer *insert_buffer,
				struct iio_buffer *remove_buffer)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_device_config new_config;
	int ret;

	ret = iio_verify_update(indio_dev, insert_buffer, remove_buffer,
				&new_config);
	if (ret)
		return ret;

	if (insert_buffer) {
		ret = iio_buffer_request_update(indio_dev, insert_buffer);
		if (ret)
			goto err_free_config;
	}

	ret = iio_disable_buffers(indio_dev);
	if (ret)
		goto err_deactivate_all;

	if (remove_buffer)
		iio_buffer_deactivate(remove_buffer);
	if (insert_buffer)
		iio_buffer_activate(indio_dev, insert_buffer);

	/* If no buffers in list, we are done */
	if (list_empty(&iio_dev_opaque->buffer_list))
		return 0;

	ret = iio_enable_buffers(indio_dev, &new_config);
	if (ret)
		goto err_deactivate_all;

	return 0;

err_deactivate_all:
	/*
	 * We've already verified that the config is valid earlier. If things go
	 * wrong in either enable or disable the most likely reason is an IO
	 * error from the device. In this case there is no good recovery
	 * strategy. Just make sure to disable everything and leave the device
	 * in a sane state.  With a bit of luck the device might come back to
	 * life again later and userspace can try again.
	 */
	iio_buffer_deactivate_all(indio_dev);

err_free_config:
	iio_free_scan_mask(indio_dev, new_config.scan_mask);
	return ret;
}

int iio_update_buffers(struct iio_dev *indio_dev,
		       struct iio_buffer *insert_buffer,
		       struct iio_buffer *remove_buffer)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	int ret;

	if (insert_buffer == remove_buffer)
		return 0;

	if (insert_buffer &&
	    insert_buffer->direction == IIO_BUFFER_DIRECTION_OUT)
		return -EINVAL;

	mutex_lock(&iio_dev_opaque->info_exist_lock);
	mutex_lock(&iio_dev_opaque->mlock);

	if (insert_buffer && iio_buffer_is_active(insert_buffer))
		insert_buffer = NULL;

	if (remove_buffer && !iio_buffer_is_active(remove_buffer))
		remove_buffer = NULL;

	if (!insert_buffer && !remove_buffer) {
		ret = 0;
		goto out_unlock;
	}

	if (!indio_dev->info) {
		ret = -ENODEV;
		goto out_unlock;
	}

	ret = __iio_update_buffers(indio_dev, insert_buffer, remove_buffer);

out_unlock:
	mutex_unlock(&iio_dev_opaque->mlock);
	mutex_unlock(&iio_dev_opaque->info_exist_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(iio_update_buffers);

void iio_disable_all_buffers(struct iio_dev *indio_dev)
{
	iio_disable_buffers(indio_dev);
	iio_buffer_deactivate_all(indio_dev);
}

static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
			    const char *buf, size_t len)
{
	int ret;
	bool requested_state;
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
	bool inlist;

	ret = kstrtobool(buf, &requested_state);
	if (ret < 0)
		return ret;

	mutex_lock(&iio_dev_opaque->mlock);

	/* Find out if it is in the list */
	inlist = iio_buffer_is_active(buffer);
	/* Already in desired state */
	if (inlist == requested_state)
		goto done;

	if (requested_state)
		ret = __iio_update_buffers(indio_dev, buffer, NULL);
	else
		ret = __iio_update_buffers(indio_dev, NULL, buffer);

done:
	mutex_unlock(&iio_dev_opaque->mlock);
	return (ret < 0) ? ret : len;
}

static ssize_t watermark_show(struct device *dev, struct device_attribute *attr,
			      char *buf)
{
	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

	return sysfs_emit(buf, "%u\n", buffer->watermark);
}

static ssize_t watermark_store(struct device *dev,
			       struct device_attribute *attr,
			       const char *buf, size_t len)
{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
	unsigned int val;
	int ret;

	ret = kstrtouint(buf, 10, &val);
	if (ret)
		return ret;
	if (!val)
		return -EINVAL;

	mutex_lock(&iio_dev_opaque->mlock);

	if (val > buffer->length) {
		ret = -EINVAL;
		goto out;
	}

	if (iio_buffer_is_active(buffer)) {
		ret = -EBUSY;
		goto out;
	}

	buffer->watermark = val;
out:
	mutex_unlock(&iio_dev_opaque->mlock);

	return ret ? ret : len;
}

static ssize_t data_available_show(struct device *dev,
				   struct device_attribute *attr, char *buf)
{
	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

	return sysfs_emit(buf, "%zu\n", iio_buffer_data_available(buffer));
}

static ssize_t direction_show(struct device *dev,
			      struct device_attribute *attr,
			      char *buf)
{
	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

	switch (buffer->direction) {
	case IIO_BUFFER_DIRECTION_IN:
		return sysfs_emit(buf, "in\n");
	case IIO_BUFFER_DIRECTION_OUT:
		return sysfs_emit(buf, "out\n");
	default:
		return -EINVAL;
	}
}

static DEVICE_ATTR_RW(length);
static struct device_attribute dev_attr_length_ro = __ATTR_RO(length);
static DEVICE_ATTR_RW(enable);
static DEVICE_ATTR_RW(watermark);
static struct device_attribute dev_attr_watermark_ro = __ATTR_RO(watermark);
static DEVICE_ATTR_RO(data_available);
static DEVICE_ATTR_RO(direction);

/*
 * When adding new attributes here, put the at the end, at least until
 * the code that handles the length/length_ro & watermark/watermark_ro
 * assignments gets cleaned up. Otherwise these can create some weird
 * duplicate attributes errors under some setups.
 */
static struct attribute *iio_buffer_attrs[] = {
	&dev_attr_length.attr,
	&dev_attr_enable.attr,
	&dev_attr_watermark.attr,
	&dev_attr_data_available.attr,
	&dev_attr_direction.attr,
};

#define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)

static struct attribute *iio_buffer_wrap_attr(struct iio_buffer *buffer,
					      struct attribute *attr)
{
	struct device_attribute *dattr = to_dev_attr(attr);
	struct iio_dev_attr *iio_attr;

	iio_attr = kzalloc(sizeof(*iio_attr), GFP_KERNEL);
	if (!iio_attr)
		return NULL;

	iio_attr->buffer = buffer;
	memcpy(&iio_attr->dev_attr, dattr, sizeof(iio_attr->dev_attr));
	iio_attr->dev_attr.attr.name = kstrdup_const(attr->name, GFP_KERNEL);
	if (!iio_attr->dev_attr.attr.name) {
		kfree(iio_attr);
		return NULL;
	}

	sysfs_attr_init(&iio_attr->dev_attr.attr);

	list_add(&iio_attr->l, &buffer->buffer_attr_list);

	return &iio_attr->dev_attr.attr;
}

static int iio_buffer_register_legacy_sysfs_groups(struct iio_dev *indio_dev,
						   struct attribute **buffer_attrs,
						   int buffer_attrcount,
						   int scan_el_attrcount)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct attribute_group *group;
	struct attribute **attrs;
	int ret;

	attrs = kcalloc(buffer_attrcount + 1, sizeof(*attrs), GFP_KERNEL);
	if (!attrs)
		return -ENOMEM;

	memcpy(attrs, buffer_attrs, buffer_attrcount * sizeof(*attrs));

	group = &iio_dev_opaque->legacy_buffer_group;
	group->attrs = attrs;
	group->name = "buffer";

	ret = iio_device_register_sysfs_group(indio_dev, group);
	if (ret)
		goto error_free_buffer_attrs;

	attrs = kcalloc(scan_el_attrcount + 1, sizeof(*attrs), GFP_KERNEL);
	if (!attrs) {
		ret = -ENOMEM;
		goto error_free_buffer_attrs;
	}

	memcpy(attrs, &buffer_attrs[buffer_attrcount],
	       scan_el_attrcount * sizeof(*attrs));

	group = &iio_dev_opaque->legacy_scan_el_group;
	group->attrs = attrs;
	group->name = "scan_elements";

	ret = iio_device_register_sysfs_group(indio_dev, group);
	if (ret)
		goto error_free_scan_el_attrs;

	return 0;

error_free_scan_el_attrs:
	kfree(iio_dev_opaque->legacy_scan_el_group.attrs);
error_free_buffer_attrs:
	kfree(iio_dev_opaque->legacy_buffer_group.attrs);

	return ret;
}

static void iio_buffer_unregister_legacy_sysfs_groups(struct iio_dev *indio_dev)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);

	kfree(iio_dev_opaque->legacy_buffer_group.attrs);
	kfree(iio_dev_opaque->legacy_scan_el_group.attrs);
}

static int iio_buffer_chrdev_release(struct inode *inode, struct file *filep)
{
	struct iio_dev_buffer_pair *ib = filep->private_data;
	struct iio_dev *indio_dev = ib->indio_dev;
	struct iio_buffer *buffer = ib->buffer;

	wake_up(&buffer->pollq);

	kfree(ib);
	clear_bit(IIO_BUSY_BIT_POS, &buffer->flags);
	iio_device_put(indio_dev);

	return 0;
}

static const struct file_operations iio_buffer_chrdev_fileops = {
	.owner = THIS_MODULE,
	.llseek = noop_llseek,
	.read = iio_buffer_read,
	.write = iio_buffer_write,
	.poll = iio_buffer_poll,
	.release = iio_buffer_chrdev_release,
};

static long iio_device_buffer_getfd(struct iio_dev *indio_dev, unsigned long arg)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	int __user *ival = (int __user *)arg;
	struct iio_dev_buffer_pair *ib;
	struct iio_buffer *buffer;
	int fd, idx, ret;

	if (copy_from_user(&idx, ival, sizeof(idx)))
		return -EFAULT;

	if (idx >= iio_dev_opaque->attached_buffers_cnt)
		return -ENODEV;

	iio_device_get(indio_dev);

	buffer = iio_dev_opaque->attached_buffers[idx];

	if (test_and_set_bit(IIO_BUSY_BIT_POS, &buffer->flags)) {
		ret = -EBUSY;
		goto error_iio_dev_put;
	}

	ib = kzalloc(sizeof(*ib), GFP_KERNEL);
	if (!ib) {
		ret = -ENOMEM;
		goto error_clear_busy_bit;
	}

	ib->indio_dev = indio_dev;
	ib->buffer = buffer;

	fd = anon_inode_getfd("iio:buffer", &iio_buffer_chrdev_fileops,
			      ib, O_RDWR | O_CLOEXEC);
	if (fd < 0) {
		ret = fd;
		goto error_free_ib;
	}

	if (copy_to_user(ival, &fd, sizeof(fd))) {
		/*
		 * "Leak" the fd, as there's not much we can do about this
		 * anyway. 'fd' might have been closed already, as
		 * anon_inode_getfd() called fd_install() on it, which made
		 * it reachable by userland.
		 *
		 * Instead of allowing a malicious user to play tricks with
		 * us, rely on the process exit path to do any necessary
		 * cleanup, as in releasing the file, if still needed.
		 */
		return -EFAULT;
	}

	return 0;

error_free_ib:
	kfree(ib);
error_clear_busy_bit:
	clear_bit(IIO_BUSY_BIT_POS, &buffer->flags);
error_iio_dev_put:
	iio_device_put(indio_dev);
	return ret;
}

static long iio_device_buffer_ioctl(struct iio_dev *indio_dev, struct file *filp,
				    unsigned int cmd, unsigned long arg)
{
	switch (cmd) {
	case IIO_BUFFER_GET_FD_IOCTL:
		return iio_device_buffer_getfd(indio_dev, arg);
	default:
		return IIO_IOCTL_UNHANDLED;
	}
}

static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
					     struct iio_dev *indio_dev,
					     int index)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_dev_attr *p;
	const struct iio_dev_attr *id_attr;
	struct attribute **attr;
	int ret, i, attrn, scan_el_attrcount, buffer_attrcount;
	const struct iio_chan_spec *channels;

	buffer_attrcount = 0;
	if (buffer->attrs) {
		while (buffer->attrs[buffer_attrcount])
			buffer_attrcount++;
	}
	buffer_attrcount += ARRAY_SIZE(iio_buffer_attrs);

	scan_el_attrcount = 0;
	INIT_LIST_HEAD(&buffer->buffer_attr_list);
	channels = indio_dev->channels;
	if (channels) {
		/* new magic */
		for (i = 0; i < indio_dev->num_channels; i++) {
			if (channels[i].scan_index < 0)
				continue;

			/* Verify that sample bits fit into storage */
			if (channels[i].scan_type.storagebits <
			    channels[i].scan_type.realbits +
			    channels[i].scan_type.shift) {
				dev_err(&indio_dev->dev,
					"Channel %d storagebits (%d) < shifted realbits (%d + %d)\n",
					i, channels[i].scan_type.storagebits,
					channels[i].scan_type.realbits,
					channels[i].scan_type.shift);
				ret = -EINVAL;
				goto error_cleanup_dynamic;
			}

			ret = iio_buffer_add_channel_sysfs(indio_dev, buffer,
							   &channels[i]);
			if (ret < 0)
				goto error_cleanup_dynamic;
			scan_el_attrcount += ret;
			if (channels[i].type == IIO_TIMESTAMP)
				iio_dev_opaque->scan_index_timestamp =
					channels[i].scan_index;
		}
		if (indio_dev->masklength && !buffer->scan_mask) {
			buffer->scan_mask = bitmap_zalloc(indio_dev->masklength,
							  GFP_KERNEL);
			if (!buffer->scan_mask) {
				ret = -ENOMEM;
				goto error_cleanup_dynamic;
			}
		}
	}

	attrn = buffer_attrcount + scan_el_attrcount;
	attr = kcalloc(attrn + 1, sizeof(*attr), GFP_KERNEL);
	if (!attr) {
		ret = -ENOMEM;
		goto error_free_scan_mask;
	}

	memcpy(attr, iio_buffer_attrs, sizeof(iio_buffer_attrs));
	if (!buffer->access->set_length)
		attr[0] = &dev_attr_length_ro.attr;

	if (buffer->access->flags & INDIO_BUFFER_FLAG_FIXED_WATERMARK)
		attr[2] = &dev_attr_watermark_ro.attr;

	if (buffer->attrs)
		for (i = 0, id_attr = buffer->attrs[i];
		     (id_attr = buffer->attrs[i]); i++)
			attr[ARRAY_SIZE(iio_buffer_attrs) + i] =
				(struct attribute *)&id_attr->dev_attr.attr;

	buffer->buffer_group.attrs = attr;

	for (i = 0; i < buffer_attrcount; i++) {
		struct attribute *wrapped;

		wrapped = iio_buffer_wrap_attr(buffer, attr[i]);
		if (!wrapped) {
			ret = -ENOMEM;
			goto error_free_buffer_attrs;
		}
		attr[i] = wrapped;
	}

	attrn = 0;
	list_for_each_entry(p, &buffer->buffer_attr_list, l)
		attr[attrn++] = &p->dev_attr.attr;

	buffer->buffer_group.name = kasprintf(GFP_KERNEL, "buffer%d", index);
	if (!buffer->buffer_group.name) {
		ret = -ENOMEM;
		goto error_free_buffer_attrs;
	}

	ret = iio_device_register_sysfs_group(indio_dev, &buffer->buffer_group);
	if (ret)
		goto error_free_buffer_attr_group_name;

	/* we only need to register the legacy groups for the first buffer */
	if (index > 0)
		return 0;

	ret = iio_buffer_register_legacy_sysfs_groups(indio_dev, attr,
						      buffer_attrcount,
						      scan_el_attrcount);
	if (ret)
		goto error_free_buffer_attr_group_name;

	return 0;

error_free_buffer_attr_group_name:
	kfree(buffer->buffer_group.name);
error_free_buffer_attrs:
	kfree(buffer->buffer_group.attrs);
error_free_scan_mask:
	bitmap_free(buffer->scan_mask);
error_cleanup_dynamic:
	iio_free_chan_devattr_list(&buffer->buffer_attr_list);

	return ret;
}

static void __iio_buffer_free_sysfs_and_mask(struct iio_buffer *buffer,
					     struct iio_dev *indio_dev,
					     int index)
{
	if (index == 0)
		iio_buffer_unregister_legacy_sysfs_groups(indio_dev);
	bitmap_free(buffer->scan_mask);
	kfree(buffer->buffer_group.name);
	kfree(buffer->buffer_group.attrs);
	iio_free_chan_devattr_list(&buffer->buffer_attr_list);
}

int iio_buffers_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	const struct iio_chan_spec *channels;
	struct iio_buffer *buffer;
	int ret, i, idx;
	size_t sz;

	channels = indio_dev->channels;
	if (channels) {
		int ml = indio_dev->masklength;

		for (i = 0; i < indio_dev->num_channels; i++)
			ml = max(ml, channels[i].scan_index + 1);
		indio_dev->masklength = ml;
	}

	if (!iio_dev_opaque->attached_buffers_cnt)
		return 0;

	for (idx = 0; idx < iio_dev_opaque->attached_buffers_cnt; idx++) {
		buffer = iio_dev_opaque->attached_buffers[idx];
		ret = __iio_buffer_alloc_sysfs_and_mask(buffer, indio_dev, idx);
		if (ret)
			goto error_unwind_sysfs_and_mask;
	}

	sz = sizeof(*iio_dev_opaque->buffer_ioctl_handler);
	iio_dev_opaque->buffer_ioctl_handler = kzalloc(sz, GFP_KERNEL);
	if (!iio_dev_opaque->buffer_ioctl_handler) {
		ret = -ENOMEM;
		goto error_unwind_sysfs_and_mask;
	}

	iio_dev_opaque->buffer_ioctl_handler->ioctl = iio_device_buffer_ioctl;
	iio_device_ioctl_handler_register(indio_dev,
					  iio_dev_opaque->buffer_ioctl_handler);

	return 0;

error_unwind_sysfs_and_mask:
	while (idx--) {
		buffer = iio_dev_opaque->attached_buffers[idx];
		__iio_buffer_free_sysfs_and_mask(buffer, indio_dev, idx);
	}
	return ret;
}

void iio_buffers_free_sysfs_and_mask(struct iio_dev *indio_dev)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer *buffer;
	int i;

	if (!iio_dev_opaque->attached_buffers_cnt)
		return;

	iio_device_ioctl_handler_unregister(iio_dev_opaque->buffer_ioctl_handler);
	kfree(iio_dev_opaque->buffer_ioctl_handler);

	for (i = iio_dev_opaque->attached_buffers_cnt - 1; i >= 0; i--) {
		buffer = iio_dev_opaque->attached_buffers[i];
		__iio_buffer_free_sysfs_and_mask(buffer, indio_dev, i);
	}
}

/**
 * iio_validate_scan_mask_onehot() - Validates that exactly one channel is selected
 * @indio_dev: the iio device
 * @mask: scan mask to be checked
 *
 * Return true if exactly one bit is set in the scan mask, false otherwise. It
 * can be used for devices where only one channel can be active for sampling at
 * a time.
 */
bool iio_validate_scan_mask_onehot(struct iio_dev *indio_dev,
				   const unsigned long *mask)
{
	return bitmap_weight(mask, indio_dev->masklength) == 1;
}
EXPORT_SYMBOL_GPL(iio_validate_scan_mask_onehot);

static const void *iio_demux(struct iio_buffer *buffer,
			     const void *datain)
{
	struct iio_demux_table *t;

	if (list_empty(&buffer->demux_list))
		return datain;
	list_for_each_entry(t, &buffer->demux_list, l)
		memcpy(buffer->demux_bounce + t->to,
		       datain + t->from, t->length);

	return buffer->demux_bounce;
}

static int iio_push_to_buffer(struct iio_buffer *buffer, const void *data)
{
	const void *dataout = iio_demux(buffer, data);
	int ret;

	ret = buffer->access->store_to(buffer, dataout);
	if (ret)
		return ret;

	/*
	 * We can't just test for watermark to decide if we wake the poll queue
	 * because read may request less samples than the watermark.
	 */
	wake_up_interruptible_poll(&buffer->pollq, EPOLLIN | EPOLLRDNORM);
	return 0;
}

/**
 * iio_push_to_buffers() - push to a registered buffer.
 * @indio_dev:		iio_dev structure for device.
 * @data:		Full scan.
 */
int iio_push_to_buffers(struct iio_dev *indio_dev, const void *data)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	int ret;
	struct iio_buffer *buf;

	list_for_each_entry(buf, &iio_dev_opaque->buffer_list, buffer_list) {
		ret = iio_push_to_buffer(buf, data);
		if (ret < 0)
			return ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(iio_push_to_buffers);

/**
 * iio_push_to_buffers_with_ts_unaligned() - push to registered buffer,
 *    no alignment or space requirements.
 * @indio_dev:		iio_dev structure for device.
 * @data:		channel data excluding the timestamp.
 * @data_sz:		size of data.
 * @timestamp:		timestamp for the sample data.
 *
 * This special variant of iio_push_to_buffers_with_timestamp() does
 * not require space for the timestamp, or 8 byte alignment of data.
 * It does however require an allocation on first call and additional
 * copies on all calls, so should be avoided if possible.
 */
int iio_push_to_buffers_with_ts_unaligned(struct iio_dev *indio_dev,
					  const void *data,
					  size_t data_sz,
					  int64_t timestamp)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);

	/*
	 * Conservative estimate - we can always safely copy the minimum
	 * of either the data provided or the length of the destination buffer.
	 * This relaxed limit allows the calling drivers to be lax about
	 * tracking the size of the data they are pushing, at the cost of
	 * unnecessary copying of padding.
	 */
	data_sz = min_t(size_t, indio_dev->scan_bytes, data_sz);
	if (iio_dev_opaque->bounce_buffer_size !=  indio_dev->scan_bytes) {
		void *bb;

		bb = devm_krealloc(&indio_dev->dev,
				   iio_dev_opaque->bounce_buffer,
				   indio_dev->scan_bytes, GFP_KERNEL);
		if (!bb)
			return -ENOMEM;
		iio_dev_opaque->bounce_buffer = bb;
		iio_dev_opaque->bounce_buffer_size = indio_dev->scan_bytes;
	}
	memcpy(iio_dev_opaque->bounce_buffer, data, data_sz);
	return iio_push_to_buffers_with_timestamp(indio_dev,
						  iio_dev_opaque->bounce_buffer,
						  timestamp);
}
EXPORT_SYMBOL_GPL(iio_push_to_buffers_with_ts_unaligned);

/**
 * iio_buffer_release() - Free a buffer's resources
 * @ref: Pointer to the kref embedded in the iio_buffer struct
 *
 * This function is called when the last reference to the buffer has been
 * dropped. It will typically free all resources allocated by the buffer. Do not
 * call this function manually, always use iio_buffer_put() when done using a
 * buffer.
 */
static void iio_buffer_release(struct kref *ref)
{
	struct iio_buffer *buffer = container_of(ref, struct iio_buffer, ref);

	buffer->access->release(buffer);
}

/**
 * iio_buffer_get() - Grab a reference to the buffer
 * @buffer: The buffer to grab a reference for, may be NULL
 *
 * Returns the pointer to the buffer that was passed into the function.
 */
struct iio_buffer *iio_buffer_get(struct iio_buffer *buffer)
{
	if (buffer)
		kref_get(&buffer->ref);

	return buffer;
}
EXPORT_SYMBOL_GPL(iio_buffer_get);

/**
 * iio_buffer_put() - Release the reference to the buffer
 * @buffer: The buffer to release the reference for, may be NULL
 */
void iio_buffer_put(struct iio_buffer *buffer)
{
	if (buffer)
		kref_put(&buffer->ref, iio_buffer_release);
}
EXPORT_SYMBOL_GPL(iio_buffer_put);

/**
 * iio_device_attach_buffer - Attach a buffer to a IIO device
 * @indio_dev: The device the buffer should be attached to
 * @buffer: The buffer to attach to the device
 *
 * Return 0 if successful, negative if error.
 *
 * This function attaches a buffer to a IIO device. The buffer stays attached to
 * the device until the device is freed. For legacy reasons, the first attached
 * buffer will also be assigned to 'indio_dev->buffer'.
 * The array allocated here, will be free'd via the iio_device_detach_buffers()
 * call which is handled by the iio_device_free().
 */
int iio_device_attach_buffer(struct iio_dev *indio_dev,
			     struct iio_buffer *buffer)
{
	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
	struct iio_buffer **new, **old = iio_dev_opaque->attached_buffers;
	unsigned int cnt = iio_dev_opaque->attached_buffers_cnt;

	cnt++;

	new = krealloc(old, sizeof(*new) * cnt, GFP_KERNEL);
	if (!new)
		return -ENOMEM;
	iio_dev_opaque->attached_buffers = new;

	buffer = iio_buffer_get(buffer);

	/* first buffer is legacy; attach it to the IIO device directly */
	if (!indio_dev->buffer)
		indio_dev->buffer = buffer;

	iio_dev_opaque->attached_buffers[cnt - 1] = buffer;
	iio_dev_opaque->attached_buffers_cnt = cnt;

	return 0;
}
EXPORT_SYMBOL_GPL(iio_device_attach_buffer);