summaryrefslogtreecommitdiff
path: root/src/libcamera/v4l2_videodevice.cpp
blob: 430715afd55416de76a8ad2a0c09cd3fbb60047f (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
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * v4l2_videodevice.cpp - V4L2 Video Device
 */

#include "libcamera/internal/v4l2_videodevice.h"

#include <algorithm>
#include <array>
#include <fcntl.h>
#include <iomanip>
#include <sstream>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <unistd.h>
#include <vector>

#include <linux/version.h>

#include <libcamera/base/event_notifier.h>
#include <libcamera/base/log.h>
#include <libcamera/base/shared_fd.h>
#include <libcamera/base/unique_fd.h>
#include <libcamera/base/utils.h>

#include "libcamera/internal/formats.h"
#include "libcamera/internal/framebuffer.h"
#include "libcamera/internal/media_device.h"
#include "libcamera/internal/media_object.h"

/**
 * \file v4l2_videodevice.h
 * \brief V4L2 Video Device
 */

namespace libcamera {

LOG_DECLARE_CATEGORY(V4L2)

/**
 * \struct V4L2Capability
 * \brief struct v4l2_capability object wrapper and helpers
 *
 * The V4L2Capability structure manages the information returned by the
 * VIDIOC_QUERYCAP ioctl.
 */

/**
 * \fn V4L2Capability::driver()
 * \brief Retrieve the driver module name
 * \return The string containing the name of the driver module
 */

/**
 * \fn V4L2Capability::card()
 * \brief Retrieve the video device card name
 * \return The string containing the video device name
 */

/**
 * \fn V4L2Capability::bus_info()
 * \brief Retrieve the location of the video device in the system
 * \return The string containing the video device location
 */

/**
 * \fn V4L2Capability::device_caps()
 * \brief Retrieve the capabilities of the video device
 * \return The video device specific capabilities if V4L2_CAP_DEVICE_CAPS is
 * set or driver capabilities otherwise
 */

/**
 * \fn V4L2Capability::isMultiplanar()
 * \brief Identify if the video device implements the V4L2 multiplanar APIs
 * \return True if the video device supports multiplanar APIs
 */

/**
 * \fn V4L2Capability::isCapture()
 * \brief Identify if the video device captures data
 * \return True if the video device can capture data
 */

/**
 * \fn V4L2Capability::isOutput()
 * \brief Identify if the video device outputs data
 * \return True if the video device can output data
 */

/**
 * \fn V4L2Capability::isVideo()
 * \brief Identify if the video device captures or outputs images
 * \return True if the video device can capture or output images
 */

/**
 * \fn V4L2Capability::isM2M()
 * \brief Identify if the device is a Memory-to-Memory device
 * \return True if the device can capture and output images using the M2M API
 */

/**
 * \fn V4L2Capability::isMeta()
 * \brief Identify if the video device captures or outputs image meta-data
 * \return True if the video device can capture or output image meta-data
 */

/**
 * \fn V4L2Capability::isVideoCapture()
 * \brief Identify if the video device captures images
 * \return True if the video device can capture images
 */

/**
 * \fn V4L2Capability::isVideoOutput()
 * \brief Identify if the video device outputs images
 * \return True if the video device can output images
 */

/**
 * \fn V4L2Capability::isMetaCapture()
 * \brief Identify if the video device captures image meta-data
 * \return True if the video device can capture image meta-data
 */

/**
 * \fn V4L2Capability::isMetaOutput()
 * \brief Identify if the video device outputs image meta-data
 * \return True if the video device can output image meta-data
 */

/**
 * \fn V4L2Capability::hasStreaming()
 * \brief Determine if the video device can perform Streaming I/O
 * \return True if the video device provides Streaming I/O IOCTLs
 */

/**
 * \fn V4L2Capability::hasMediaController()
 * \brief Determine if the video device uses Media Controller to configure I/O
 * \return True if the video device is controlled by a Media Controller device
 */

/**
 * \class V4L2BufferCache
 * \brief Hot cache of associations between V4L2 buffer indexes and FrameBuffer
 *
 * When importing buffers, V4L2 performs lazy mapping of dmabuf instances at
 * VIDIOC_QBUF (or VIDIOC_PREPARE_BUF) time and keeps the mapping associated
 * with the V4L2 buffer, as identified by its index. If the same V4L2 buffer is
 * then reused and queued with different dmabufs, the old dmabufs will be
 * unmapped and the new ones mapped. To keep this process efficient, it is
 * crucial to consistently use the same V4L2 buffer for given dmabufs through
 * the whole duration of a capture cycle.
 *
 * The V4L2BufferCache class keeps a map of previous dmabufs to V4L2 buffer
 * index associations to help selecting V4L2 buffers. It tracks, for every
 * entry, if the V4L2 buffer is in use, and offers lookup of the best free V4L2
 * buffer for a set of dmabufs.
 */

/**
 * \brief Create an empty cache with \a numEntries entries
 * \param[in] numEntries Number of entries to reserve in the cache
 *
 * Create a cache with \a numEntries entries all marked as unused. The entries
 * will be populated as the cache is used. This is typically used to implement
 * buffer import, with buffers added to the cache as they are queued.
 */
V4L2BufferCache::V4L2BufferCache(unsigned int numEntries)
	: lastUsedCounter_(1), missCounter_(0)
{
	cache_.resize(numEntries);
}

/**
 * \brief Create a pre-populated cache
 * \param[in] buffers Array of buffers to pre-populated with
 *
 * Create a cache pre-populated with \a buffers. This is typically used to
 * implement buffer export, with all buffers added to the cache when they are
 * allocated.
 */
V4L2BufferCache::V4L2BufferCache(const std::vector<std::unique_ptr<FrameBuffer>> &buffers)
	: lastUsedCounter_(1), missCounter_(0)
{
	for (const std::unique_ptr<FrameBuffer> &buffer : buffers)
		cache_.emplace_back(true,
				    lastUsedCounter_.fetch_add(1, std::memory_order_acq_rel),
				    *buffer.get());
}

V4L2BufferCache::~V4L2BufferCache()
{
	if (missCounter_ > cache_.size())
		LOG(V4L2, Debug) << "Cache misses: " << missCounter_;
}

/**
 * \brief Check if all the entries in the cache are unused
 */
bool V4L2BufferCache::isEmpty() const
{
	for (auto const &entry : cache_) {
		if (!entry.free_)
			return false;
	}

	return true;
}

/**
 * \brief Find the best V4L2 buffer for a FrameBuffer
 * \param[in] buffer The FrameBuffer
 *
 * Find the best V4L2 buffer index to be used for the FrameBuffer \a buffer
 * based on previous mappings of frame buffers to V4L2 buffers. If a free V4L2
 * buffer previously used with the same dmabufs as \a buffer is found in the
 * cache, return its index. Otherwise return the index of the first free V4L2
 * buffer and record its association with the dmabufs of \a buffer.
 *
 * \return The index of the best V4L2 buffer, or -ENOENT if no free V4L2 buffer
 * is available
 */
int V4L2BufferCache::get(const FrameBuffer &buffer)
{
	bool hit = false;
	int use = -1;
	uint64_t oldest = UINT64_MAX;

	for (unsigned int index = 0; index < cache_.size(); index++) {
		const Entry &entry = cache_[index];

		if (!entry.free_)
			continue;

		/* Try to find a cache hit by comparing the planes. */
		if (entry == buffer) {
			hit = true;
			use = index;
			break;
		}

		if (entry.lastUsed_ < oldest) {
			use = index;
			oldest = entry.lastUsed_;
		}
	}

	if (!hit)
		missCounter_++;

	if (use < 0)
		return -ENOENT;

	cache_[use] = Entry(false,
			    lastUsedCounter_.fetch_add(1, std::memory_order_acq_rel),
			    buffer);

	return use;
}

/**
 * \brief Mark buffer \a index as free in the cache
 * \param[in] index The V4L2 buffer index
 */
void V4L2BufferCache::put(unsigned int index)
{
	ASSERT(index < cache_.size());
	cache_[index].free_ = true;
}

V4L2BufferCache::Entry::Entry()
	: free_(true), lastUsed_(0)
{
}

V4L2BufferCache::Entry::Entry(bool free, uint64_t lastUsed, const FrameBuffer &buffer)
	: free_(free), lastUsed_(lastUsed)
{
	for (const FrameBuffer::Plane &plane : buffer.planes())
		planes_.emplace_back(plane);
}

bool V4L2BufferCache::Entry::operator==(const FrameBuffer &buffer) const
{
	const std::vector<FrameBuffer::Plane> &planes = buffer.planes();

	if (planes_.size() != planes.size())
		return false;

	for (unsigned int i = 0; i < planes.size(); i++)
		if (planes_[i].fd != planes[i].fd.get() ||
		    planes_[i].length != planes[i].length)
			return false;
	return true;
}

/**
 * \class V4L2DeviceFormat
 * \brief The V4L2 video device image format and sizes
 *
 * This class describes the image format and resolution to be programmed on a
 * V4L2 video device. The image format is defined by a fourcc code (as specified
 * by the V4L2 API with the V4L2_PIX_FMT_* macros), a resolution (width and
 * height) and one to three planes with configurable line stride and a total
 * per-plane size in bytes.
 *
 * Image formats, as defined by the V4L2 APIs, are categorised as packed,
 * semi-planar and planar, and describe the layout of the image pixel components
 * stored in memory.
 *
 * Packed image formats store pixel components one after the other, in a
 * contiguous memory area. Examples of packed image formats are YUYV
 * permutations, RGB with different pixel sub-sampling ratios such as RGB565 or
 * RGB666 or Raw-Bayer formats such as SRGGB8 or SGRBG12.
 *
 * Semi-planar and planar image formats store the pixel components in separate
 * and possibly non-contiguous memory areas, named planes, whose sizes depend on
 * the pixel components sub-sampling ratios, which are defined by the format.
 * Semi-planar formats use two planes to store pixel components and notable
 * examples of such formats are the NV12 and NV16 formats, while planar formats
 * use three planes to store pixel components and notable examples are YUV422
 * and YUV420.
 *
 * Image formats supported by the V4L2 API are defined and described in Section
 * number 2 of the "Part I - Video for Linux API" chapter of the "Linux Media
 * Infrastructure userspace API", part of the Linux kernel documentation.
 *
 * In the context of this document, packed image formats are referred to as
 * "packed formats" and semi-planar and planar image formats are referred to as
 * "planar formats".
 *
 * V4L2 also defines two different sets of APIs to work with devices that store
 * planes in contiguous or separate memory areas. They are named "Single-plane
 * APIs" and "Multi-plane APIs" respectively and are documented in Section 2.1
 * and Section 2.2 of the above mentioned "Part I - Video for Linux API"
 * documentation.
 *
 * The single-plane API allows, among other parameters, the configuration of the
 * image resolution, the pixel format and the stride length. In that case the
 * stride applies to all planes (possibly sub-sampled). The multi-plane API
 * allows configuring the resolution, the pixel format and a per-plane stride
 * length and total size.
 *
 * Packed image formats, which occupy a single memory area, are easily described
 * through the single-plane API. When used on a video device that implements the
 * multi-plane API, only the size and stride information contained in the first
 * plane are taken into account.
 *
 * Planar image formats, which occupy distinct memory areas, are easily
 * described through the multi-plane APIs. When used on a video device that
 * implements the single-plane API, all planes are stored one after the other
 * in a contiguous memory area, and it is not possible to configure per-plane
 * stride length and size, but only a global stride length which is applied to
 * all planes.
 *
 * The V4L2DeviceFormat class describes both packed and planar image formats,
 * regardless of the API type (single or multi plane) implemented by the video
 * device the format has to be applied to. The total size and bytes per line
 * of images represented with packed formats are configured using the first
 * entry of the V4L2DeviceFormat::planes array, while the per-plane size and
 * per-plane stride length of images represented with planar image formats are
 * configured using the opportune number of entries of the
 * V4L2DeviceFormat::planes array, as prescribed by the image format
 * definition (semi-planar formats use 2 entries, while planar formats use the
 * whole 3 entries). The number of valid entries of the
 * V4L2DeviceFormat::planes array is defined by the
 * V4L2DeviceFormat::planesCount value.
 */

/**
 * \struct V4L2DeviceFormat::Plane
 * \brief Per-plane memory size information
 * \var V4L2DeviceFormat::Plane::size
 * \brief The plane total memory size (in bytes)
 * \var V4L2DeviceFormat::Plane::bpl
 * \brief The plane line stride (in bytes)
 */

/**
 * \var V4L2DeviceFormat::size
 * \brief The image size in pixels
 */

/**
 * \var V4L2DeviceFormat::fourcc
 * \brief The fourcc code describing the pixel encoding scheme
 *
 * The fourcc code, as defined by the V4L2 API with the V4L2_PIX_FMT_* macros,
 * that identifies the image format pixel encoding scheme.
 */

/**
 * \var V4L2DeviceFormat::colorSpace
 * \brief The color space of the pixels
 *
 * The color space of the image. When setting the format this may be
 * unset, in which case the driver gets to use its default color space.
 * After being set, this value should contain the color space that
 * was actually used. If this value is unset, then the color space chosen
 * by the driver could not be represented by the ColorSpace class (and
 * should probably be added).
 *
 * It is up to the pipeline handler or application to check if the
 * resulting color space is acceptable.
 */

/**
 * \var V4L2DeviceFormat::planes
 * \brief The per-plane memory size information
 *
 * Images are stored in memory in one or more data planes. Each data plane has a
 * specific line stride and memory size, which could differ from the image
 * visible sizes to accommodate padding at the end of lines and end of planes.
 * Only the first \ref planesCount entries are considered valid.
 */

/**
 * \var V4L2DeviceFormat::planesCount
 * \brief The number of valid data planes
 */

/**
 * \brief Assemble and return a string describing the format
 * \return A string describing the V4L2DeviceFormat
 */
const std::string V4L2DeviceFormat::toString() const
{
	std::stringstream ss;
	ss << *this;

	return ss.str();
}

/**
 * \brief Insert a text representation of a V4L2DeviceFormat into an output
 * stream
 * \param[in] out The output stream
 * \param[in] f The V4L2DeviceFormat
 * \return The output stream \a out
 */
std::ostream &operator<<(std::ostream &out, const V4L2DeviceFormat &f)
{
	out << f.size << "-" << f.fourcc;
	return out;
}

/**
 * \class V4L2VideoDevice
 * \brief V4L2VideoDevice object and API
 *
 * The V4L2VideoDevice class models an instance of a V4L2 video device.
 * It is constructed with the path to a V4L2 video device node. The device node
 * is only opened upon a call to open() which must be checked for success.
 *
 * The video device capabilities are validated when the device is opened and the
 * device is rejected if it is not a suitable V4L2 capture or output video
 * device, or if the video device does not support streaming I/O.
 *
 * No API call other than open(), isOpen() and close() shall be called on an
 * unopened device instance.
 *
 * The V4L2VideoDevice class supports the V4L2 MMAP and DMABUF memory types:
 *
 * - The allocateBuffers() function wraps buffer allocation with the V4L2 MMAP
 *   memory type. It requests buffers from the driver, allocating the
 *   corresponding memory, and exports them as a set of FrameBuffer objects.
 *   Upon successful return the driver's internal buffer management is
 *   initialized in MMAP mode, and the video device is ready to accept
 *   queueBuffer() calls.
 *
 *   This is the most traditional V4L2 buffer management, and is mostly useful
 *   to support internal buffer pools in pipeline handlers, either for CPU
 *   consumption (such as statistics or parameters pools), or for internal
 *   image buffers shared between devices.
 *
 * - The exportBuffers() function operates similarly to allocateBuffers(), but
 *   leaves the driver's internal buffer management uninitialized. It uses the
 *   V4L2 buffer orphaning support to allocate buffers with the MMAP method,
 *   export them as a set of FrameBuffer objects, and reset the driver's
 *   internal buffer management. The video device shall be initialized with
 *   importBuffers() or allocateBuffers() before it can accept queueBuffer()
 *   calls. The exported buffers are directly usable with any V4L2 video device
 *   in DMABUF mode, or with other dmabuf importers.
 *
 *   This method is mostly useful to implement buffer allocation helpers or to
 *   allocate ancillary buffers, when a V4L2 video device is used in DMABUF
 *   mode but no other source of buffers is available. An example use case
 *   would be allocation of scratch buffers to be used in case of buffer
 *   underruns on a video device that is otherwise supplied with external
 *   buffers.
 *
 * - The importBuffers() function initializes the driver's buffer management to
 *   import buffers in DMABUF mode. It requests buffers from the driver, but
 *   doesn't allocate memory. Upon successful return, the video device is ready
 *   to accept queueBuffer() calls. The buffers to be imported are provided to
 *   queueBuffer(), and may be supplied externally, or come from a previous
 *   exportBuffers() call.
 *
 *   This is the usual buffers initialization method for video devices whose
 *   buffers are exposed outside of libcamera. It is also typically used on one
 *   of the two video device that participate in buffer sharing inside
 *   pipelines, the other video device typically using allocateBuffers().
 *
 * - The releaseBuffers() function resets the driver's internal buffer
 *   management that was initialized by a previous call to allocateBuffers() or
 *   importBuffers(). Any memory allocated by allocateBuffers() is freed.
 *   Buffer exported by exportBuffers() are not affected by this function.
 *
 * The V4L2VideoDevice class tracks queued buffers and handles buffer events. It
 * automatically dequeues completed buffers and emits the \ref bufferReady
 * signal.
 *
 * Upon destruction any device left open will be closed, and any resources
 * released.
 *
 * \context This class is \threadbound.
 */

/**
 * \typedef V4L2VideoDevice::Formats
 * \brief A map of supported V4L2 pixel formats to frame sizes
 */

/**
 * \brief Construct a V4L2VideoDevice
 * \param[in] deviceNode The file-system path to the video device node
 */
V4L2VideoDevice::V4L2VideoDevice(const std::string &deviceNode)
	: V4L2Device(deviceNode), formatInfo_(nullptr), cache_(nullptr),
	  fdBufferNotifier_(nullptr), state_(State::Stopped),
	  watchdogDuration_(0.0)
{
	/*
	 * We default to an MMAP based CAPTURE video device, however this will
	 * be updated based upon the device capabilities.
	 */
	bufferType_ = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
	memoryType_ = V4L2_MEMORY_MMAP;
}

/**
 * \brief Construct a V4L2VideoDevice from a MediaEntity
 * \param[in] entity The MediaEntity to build the video device from
 *
 * Construct a V4L2VideoDevice from a MediaEntity's device node path.
 */
V4L2VideoDevice::V4L2VideoDevice(const MediaEntity *entity)
	: V4L2VideoDevice(entity->deviceNode())
{
	watchdog_.timeout.connect(this, &V4L2VideoDevice::watchdogExpired);
}

V4L2VideoDevice::~V4L2VideoDevice()
{
	close();
}

/**
 * \brief Open the V4L2 video device node and query its capabilities
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::open()
{
	int ret;

	ret = V4L2Device::open(O_RDWR | O_NONBLOCK);
	if (ret < 0)
		return ret;

	ret = ioctl(VIDIOC_QUERYCAP, &caps_);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Failed to query device capabilities: "
			<< strerror(-ret);
		return ret;
	}

	if (caps_.version < KERNEL_VERSION(5, 0, 0)) {
		LOG(V4L2, Error)
			<< "V4L2 API v" << (caps_.version >> 16)
			<< "." << ((caps_.version >> 8) & 0xff)
			<< "." << (caps_.version & 0xff)
			<< " too old, v5.0.0 or later is required";
		return -EINVAL;
	}

	if (!caps_.hasStreaming()) {
		LOG(V4L2, Error) << "Device does not support streaming I/O";
		return -EINVAL;
	}

	/*
	 * Set buffer type and wait for read notifications on CAPTURE video
	 * devices (POLLIN), and write notifications for OUTPUT video devices
	 * (POLLOUT).
	 */
	EventNotifier::Type notifierType;

	if (caps_.isVideoCapture()) {
		notifierType = EventNotifier::Read;
		bufferType_ = caps_.isMultiplanar()
			    ? V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
			    : V4L2_BUF_TYPE_VIDEO_CAPTURE;
	} else if (caps_.isVideoOutput()) {
		notifierType = EventNotifier::Write;
		bufferType_ = caps_.isMultiplanar()
			    ? V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE
			    : V4L2_BUF_TYPE_VIDEO_OUTPUT;
	} else if (caps_.isMetaCapture()) {
		notifierType = EventNotifier::Read;
		bufferType_ = V4L2_BUF_TYPE_META_CAPTURE;
	} else if (caps_.isMetaOutput()) {
		notifierType = EventNotifier::Write;
		bufferType_ = V4L2_BUF_TYPE_META_OUTPUT;
	} else {
		LOG(V4L2, Error) << "Device is not a supported type";
		return -EINVAL;
	}

	fdBufferNotifier_ = new EventNotifier(fd(), notifierType);
	fdBufferNotifier_->activated.connect(this, &V4L2VideoDevice::bufferAvailable);
	fdBufferNotifier_->setEnabled(false);

	LOG(V4L2, Debug)
		<< "Opened device " << caps_.bus_info() << ": "
		<< caps_.driver() << ": " << caps_.card();

	ret = getFormat(&format_);
	if (ret) {
		LOG(V4L2, Error) << "Failed to get format";
		return ret;
	}

	formatInfo_ = &PixelFormatInfo::info(format_.fourcc);

	return 0;
}

/**
 * \brief Open a V4L2 video device from an opened file handle and query its
 * capabilities
 * \param[in] handle The file descriptor to set
 * \param[in] type The device type to operate on
 *
 * This function opens a video device from the existing file descriptor \a
 * handle. Like open(), this function queries the capabilities of the device,
 * but handles it according to the given device \a type instead of determining
 * its type from the capabilities. This can be used to force a given device type
 * for memory-to-memory devices.
 *
 * The file descriptor \a handle is duplicated, no reference to the original
 * handle is kept.
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::open(SharedFD handle, enum v4l2_buf_type type)
{
	int ret;

	UniqueFD newFd = handle.dup();
	if (!newFd.isValid()) {
		ret = -errno;
		LOG(V4L2, Error) << "Failed to duplicate file handle: "
				 << strerror(-ret);
		return ret;
	}

	ret = V4L2Device::setFd(std::move(newFd));
	if (ret < 0) {
		LOG(V4L2, Error) << "Failed to set file handle: "
				 << strerror(-ret);
		return ret;
	}

	ret = ioctl(VIDIOC_QUERYCAP, &caps_);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Failed to query device capabilities: "
			<< strerror(-ret);
		return ret;
	}

	if (!caps_.hasStreaming()) {
		LOG(V4L2, Error) << "Device does not support streaming I/O";
		return -EINVAL;
	}

	/*
	 * Set buffer type and wait for read notifications on CAPTURE video
	 * devices (POLLIN), and write notifications for OUTPUT video devices
	 * (POLLOUT).
	 */
	EventNotifier::Type notifierType;

	switch (type) {
	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
		notifierType = EventNotifier::Write;
		bufferType_ = caps_.isMultiplanar()
			    ? V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE
			    : V4L2_BUF_TYPE_VIDEO_OUTPUT;
		break;
	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
		notifierType = EventNotifier::Read;
		bufferType_ = caps_.isMultiplanar()
			    ? V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
			    : V4L2_BUF_TYPE_VIDEO_CAPTURE;
		break;
	default:
		LOG(V4L2, Error) << "Unsupported buffer type";
		return -EINVAL;
	}

	fdBufferNotifier_ = new EventNotifier(fd(), notifierType);
	fdBufferNotifier_->activated.connect(this, &V4L2VideoDevice::bufferAvailable);
	fdBufferNotifier_->setEnabled(false);

	LOG(V4L2, Debug)
		<< "Opened device " << caps_.bus_info() << ": "
		<< caps_.driver() << ": " << caps_.card();

	ret = getFormat(&format_);
	if (ret) {
		LOG(V4L2, Error) << "Failed to get format";
		return ret;
	}

	formatInfo_ = &PixelFormatInfo::info(format_.fourcc);

	return 0;
}

/**
 * \brief Close the video device, releasing any resources acquired by open()
 */
void V4L2VideoDevice::close()
{
	if (!isOpen())
		return;

	releaseBuffers();
	delete fdBufferNotifier_;

	formatInfo_ = nullptr;

	V4L2Device::close();
}

/**
 * \fn V4L2VideoDevice::driverName()
 * \brief Retrieve the name of the V4L2 device driver
 * \return The string containing the driver name
 */

/**
 * \fn V4L2VideoDevice::deviceName()
 * \brief Retrieve the name of the V4L2 video device
 * \return The string containing the device name
 */

/**
 * \fn V4L2VideoDevice::busName()
 * \brief Retrieve the location of the device in the system
 * \return The string containing the device location
 */

/**
 * \fn V4L2VideoDevice::caps()
 * \brief Retrieve the device V4L2 capabilities
 * \return The device V4L2 capabilities
 */

std::string V4L2VideoDevice::logPrefix() const
{
	return deviceNode() + "[" + std::to_string(fd()) +
		(V4L2_TYPE_IS_OUTPUT(bufferType_) ? ":out]" : ":cap]");
}

/**
 * \brief Retrieve the image format set on the V4L2 video device
 * \param[out] format The image format applied on the video device
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::getFormat(V4L2DeviceFormat *format)
{
	if (caps_.isMeta())
		return getFormatMeta(format);
	else if (caps_.isMultiplanar())
		return getFormatMultiplane(format);
	else
		return getFormatSingleplane(format);
}

/**
 * \brief Try an image format on the V4L2 video device
 * \param[inout] format The image format to test applicability to the video device
 *
 * Try the supplied \a format on the video device without applying it, returning
 * the format that would be applied. This is equivalent to setFormat(), except
 * that the device configuration is not changed.
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::tryFormat(V4L2DeviceFormat *format)
{
	if (caps_.isMeta())
		return trySetFormatMeta(format, false);
	else if (caps_.isMultiplanar())
		return trySetFormatMultiplane(format, false);
	else
		return trySetFormatSingleplane(format, false);
}

/**
 * \brief Configure an image format on the V4L2 video device
 * \param[inout] format The image format to apply to the video device
 *
 * Apply the supplied \a format to the video device, and return the actually
 * applied format parameters, as \ref V4L2VideoDevice::getFormat would do.
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::setFormat(V4L2DeviceFormat *format)
{
	int ret = 0;
	if (caps_.isMeta())
		ret = trySetFormatMeta(format, true);
	else if (caps_.isMultiplanar())
		ret = trySetFormatMultiplane(format, true);
	else
		ret = trySetFormatSingleplane(format, true);

	/* Cache the set format on success. */
	if (ret)
		return ret;

	format_ = *format;
	formatInfo_ = &PixelFormatInfo::info(format_.fourcc);

	return 0;
}

int V4L2VideoDevice::getFormatMeta(V4L2DeviceFormat *format)
{
	struct v4l2_format v4l2Format = {};
	struct v4l2_meta_format *pix = &v4l2Format.fmt.meta;
	int ret;

	v4l2Format.type = bufferType_;
	ret = ioctl(VIDIOC_G_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error) << "Unable to get format: " << strerror(-ret);
		return ret;
	}

	format->size.width = 0;
	format->size.height = 0;
	format->fourcc = V4L2PixelFormat(pix->dataformat);
	format->planesCount = 1;
	format->planes[0].bpl = pix->buffersize;
	format->planes[0].size = pix->buffersize;

	return 0;
}

int V4L2VideoDevice::trySetFormatMeta(V4L2DeviceFormat *format, bool set)
{
	struct v4l2_format v4l2Format = {};
	struct v4l2_meta_format *pix = &v4l2Format.fmt.meta;
	int ret;

	v4l2Format.type = bufferType_;
	pix->dataformat = format->fourcc;
	pix->buffersize = format->planes[0].size;
	ret = ioctl(set ? VIDIOC_S_FMT : VIDIOC_TRY_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error)
			<< "Unable to " << (set ? "set" : "try")
			<< " format: " << strerror(-ret);
		return ret;
	}

	/*
	 * Return to caller the format actually applied on the video device,
	 * which might differ from the requested one.
	 */
	format->size.width = 0;
	format->size.height = 0;
	format->fourcc = V4L2PixelFormat(pix->dataformat);
	format->planesCount = 1;
	format->planes[0].bpl = pix->buffersize;
	format->planes[0].size = pix->buffersize;

	return 0;
}

int V4L2VideoDevice::getFormatMultiplane(V4L2DeviceFormat *format)
{
	struct v4l2_format v4l2Format = {};
	struct v4l2_pix_format_mplane *pix = &v4l2Format.fmt.pix_mp;
	int ret;

	v4l2Format.type = bufferType_;
	ret = ioctl(VIDIOC_G_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error) << "Unable to get format: " << strerror(-ret);
		return ret;
	}

	format->size.width = pix->width;
	format->size.height = pix->height;
	format->fourcc = V4L2PixelFormat(pix->pixelformat);
	format->planesCount = pix->num_planes;
	format->colorSpace = toColorSpace(*pix);

	for (unsigned int i = 0; i < format->planesCount; ++i) {
		format->planes[i].bpl = pix->plane_fmt[i].bytesperline;
		format->planes[i].size = pix->plane_fmt[i].sizeimage;
	}

	return 0;
}

int V4L2VideoDevice::trySetFormatMultiplane(V4L2DeviceFormat *format, bool set)
{
	struct v4l2_format v4l2Format = {};
	struct v4l2_pix_format_mplane *pix = &v4l2Format.fmt.pix_mp;
	int ret;

	v4l2Format.type = bufferType_;
	pix->width = format->size.width;
	pix->height = format->size.height;
	pix->pixelformat = format->fourcc;
	pix->num_planes = format->planesCount;
	pix->field = V4L2_FIELD_NONE;
	fromColorSpace(format->colorSpace, *pix);

	ASSERT(pix->num_planes <= std::size(pix->plane_fmt));

	for (unsigned int i = 0; i < pix->num_planes; ++i) {
		pix->plane_fmt[i].bytesperline = format->planes[i].bpl;
		pix->plane_fmt[i].sizeimage = format->planes[i].size;
	}

	ret = ioctl(set ? VIDIOC_S_FMT : VIDIOC_TRY_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error)
			<< "Unable to " << (set ? "set" : "try")
			<< " format: " << strerror(-ret);
		return ret;
	}

	/*
	 * Return to caller the format actually applied on the video device,
	 * which might differ from the requested one.
	 */
	format->size.width = pix->width;
	format->size.height = pix->height;
	format->fourcc = V4L2PixelFormat(pix->pixelformat);
	format->planesCount = pix->num_planes;
	for (unsigned int i = 0; i < format->planesCount; ++i) {
		format->planes[i].bpl = pix->plane_fmt[i].bytesperline;
		format->planes[i].size = pix->plane_fmt[i].sizeimage;
	}
	format->colorSpace = toColorSpace(*pix);

	return 0;
}

int V4L2VideoDevice::getFormatSingleplane(V4L2DeviceFormat *format)
{
	struct v4l2_format v4l2Format = {};
	struct v4l2_pix_format *pix = &v4l2Format.fmt.pix;
	int ret;

	v4l2Format.type = bufferType_;
	ret = ioctl(VIDIOC_G_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error) << "Unable to get format: " << strerror(-ret);
		return ret;
	}

	format->size.width = pix->width;
	format->size.height = pix->height;
	format->fourcc = V4L2PixelFormat(pix->pixelformat);
	format->planesCount = 1;
	format->planes[0].bpl = pix->bytesperline;
	format->planes[0].size = pix->sizeimage;
	format->colorSpace = toColorSpace(*pix);

	return 0;
}

int V4L2VideoDevice::trySetFormatSingleplane(V4L2DeviceFormat *format, bool set)
{
	struct v4l2_format v4l2Format = {};
	struct v4l2_pix_format *pix = &v4l2Format.fmt.pix;
	int ret;

	v4l2Format.type = bufferType_;
	pix->width = format->size.width;
	pix->height = format->size.height;
	pix->pixelformat = format->fourcc;
	pix->bytesperline = format->planes[0].bpl;
	pix->field = V4L2_FIELD_NONE;
	fromColorSpace(format->colorSpace, *pix);

	ret = ioctl(set ? VIDIOC_S_FMT : VIDIOC_TRY_FMT, &v4l2Format);
	if (ret) {
		LOG(V4L2, Error)
			<< "Unable to " << (set ? "set" : "try")
			<< " format: " << strerror(-ret);
		return ret;
	}

	/*
	 * Return to caller the format actually applied on the device,
	 * which might differ from the requested one.
	 */
	format->size.width = pix->width;
	format->size.height = pix->height;
	format->fourcc = V4L2PixelFormat(pix->pixelformat);
	format->planesCount = 1;
	format->planes[0].bpl = pix->bytesperline;
	format->planes[0].size = pix->sizeimage;
	format->colorSpace = toColorSpace(*pix);

	return 0;
}

/**
 * \brief Enumerate all pixel formats and frame sizes
 * \param[in] code Restrict formats to this media bus code.
 *
 * Enumerate all pixel formats and frame sizes supported by the video device.
 * If the \a code argument is not zero, only formats compatible with that media
 * bus code will be enumerated.
 *
 * \return A list of the supported video device formats
 */
V4L2VideoDevice::Formats V4L2VideoDevice::formats(uint32_t code)
{
	Formats formats;

	for (V4L2PixelFormat pixelFormat : enumPixelformats(code)) {
		std::vector<SizeRange> sizes = enumSizes(pixelFormat);
		if (sizes.empty())
			return {};

		if (formats.find(pixelFormat) != formats.end()) {
			LOG(V4L2, Error)
				<< "Could not add sizes for pixel format "
				<< pixelFormat;
			return {};
		}

		formats.emplace(pixelFormat, sizes);
	}

	return formats;
}

std::vector<V4L2PixelFormat> V4L2VideoDevice::enumPixelformats(uint32_t code)
{
	std::vector<V4L2PixelFormat> formats;
	int ret;

	if (code && !caps_.hasMediaController()) {
		LOG(V4L2, Error)
			<< "Media bus code filtering not supported by the device";
		return {};
	}

	for (unsigned int index = 0; ; index++) {
		struct v4l2_fmtdesc pixelformatEnum = {};
		pixelformatEnum.index = index;
		pixelformatEnum.type = bufferType_;
		pixelformatEnum.mbus_code = code;

		ret = ioctl(VIDIOC_ENUM_FMT, &pixelformatEnum);
		if (ret)
			break;

		formats.push_back(V4L2PixelFormat(pixelformatEnum.pixelformat));
	}

	if (ret && ret != -EINVAL) {
		LOG(V4L2, Error)
			<< "Unable to enumerate pixel formats: "
			<< strerror(-ret);
		return {};
	}

	return formats;
}

std::vector<SizeRange> V4L2VideoDevice::enumSizes(V4L2PixelFormat pixelFormat)
{
	std::vector<SizeRange> sizes;
	int ret;

	for (unsigned int index = 0;; index++) {
		struct v4l2_frmsizeenum frameSize = {};
		frameSize.index = index;
		frameSize.pixel_format = pixelFormat;

		ret = ioctl(VIDIOC_ENUM_FRAMESIZES, &frameSize);
		if (ret)
			break;

		if (index != 0 &&
		    frameSize.type != V4L2_FRMSIZE_TYPE_DISCRETE) {
			LOG(V4L2, Error)
				<< "Non-zero index for non discrete type";
			return {};
		}

		switch (frameSize.type) {
		case V4L2_FRMSIZE_TYPE_DISCRETE:
			sizes.emplace_back(Size{ frameSize.discrete.width,
						 frameSize.discrete.height });
			break;
		case V4L2_FRMSIZE_TYPE_CONTINUOUS:
			sizes.emplace_back(Size{ frameSize.stepwise.min_width,
						 frameSize.stepwise.min_height },
					   Size{ frameSize.stepwise.max_width,
						 frameSize.stepwise.max_height });
			break;
		case V4L2_FRMSIZE_TYPE_STEPWISE:
			sizes.emplace_back(Size{ frameSize.stepwise.min_width,
						 frameSize.stepwise.min_height },
					   Size{ frameSize.stepwise.max_width,
						 frameSize.stepwise.max_height },
					   frameSize.stepwise.step_width,
					   frameSize.stepwise.step_height);
			break;
		default:
			LOG(V4L2, Error)
				<< "Unknown VIDIOC_ENUM_FRAMESIZES type "
				<< frameSize.type;
			return {};
		}
	}

	if (ret && ret != -EINVAL) {
		LOG(V4L2, Error)
			<< "Unable to enumerate frame sizes: "
			<< strerror(-ret);
		return {};
	}

	return sizes;
}

/**
 * \brief Set a selection rectangle \a rect for \a target
 * \param[in] target The selection target defined by the V4L2_SEL_TGT_* flags
 * \param[inout] rect The selection rectangle to be applied
 *
 * \todo Define a V4L2SelectionTarget enum for the selection target
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::setSelection(unsigned int target, Rectangle *rect)
{
	struct v4l2_selection sel = {};

	sel.type = bufferType_;
	sel.target = target;
	sel.flags = 0;

	sel.r.left = rect->x;
	sel.r.top = rect->y;
	sel.r.width = rect->width;
	sel.r.height = rect->height;

	int ret = ioctl(VIDIOC_S_SELECTION, &sel);
	if (ret < 0) {
		LOG(V4L2, Error) << "Unable to set rectangle " << target
				 << ": " << strerror(-ret);
		return ret;
	}

	rect->x = sel.r.left;
	rect->y = sel.r.top;
	rect->width = sel.r.width;
	rect->height = sel.r.height;

	return 0;
}

int V4L2VideoDevice::requestBuffers(unsigned int count,
				    enum v4l2_memory memoryType)
{
	struct v4l2_requestbuffers rb = {};
	int ret;

	rb.count = count;
	rb.type = bufferType_;
	rb.memory = memoryType;

	ret = ioctl(VIDIOC_REQBUFS, &rb);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Unable to request " << count << " buffers: "
			<< strerror(-ret);
		return ret;
	}

	if (rb.count < count) {
		LOG(V4L2, Error)
			<< "Not enough buffers provided by V4L2VideoDevice";
		requestBuffers(0, memoryType);
		return -ENOMEM;
	}

	LOG(V4L2, Debug) << rb.count << " buffers requested.";

	return 0;
}

/**
 * \brief Allocate and export buffers from the video device
 * \param[in] count Number of buffers to allocate
 * \param[out] buffers Vector to store allocated buffers
 *
 * This function wraps buffer allocation with the V4L2 MMAP memory type. It
 * requests \a count buffers from the driver, allocating the corresponding
 * memory, and exports them as a set of FrameBuffer objects in \a buffers. Upon
 * successful return the driver's internal buffer management is initialized in
 * MMAP mode, and the video device is ready to accept queueBuffer() calls.
 *
 * The number of planes and their offsets and sizes are determined by the
 * currently active format on the device as set by setFormat(). They do not map
 * to the V4L2 buffer planes, but to colour planes of the pixel format. For
 * instance, if the active format is formats::NV12, the allocated FrameBuffer
 * instances will have two planes, for the luma and chroma components,
 * regardless of whether the device uses V4L2_PIX_FMT_NV12 or
 * V4L2_PIX_FMT_NV12M.
 *
 * Buffers allocated with this function shall later be free with
 * releaseBuffers(). If buffers have already been allocated with
 * allocateBuffers() or imported with importBuffers(), this function returns
 * -EBUSY.
 *
 * \return The number of allocated buffers on success or a negative error code
 * otherwise
 * \retval -EBUSY buffers have already been allocated or imported
 */
int V4L2VideoDevice::allocateBuffers(unsigned int count,
				     std::vector<std::unique_ptr<FrameBuffer>> *buffers)
{
	int ret = createBuffers(count, buffers);
	if (ret < 0)
		return ret;

	cache_ = new V4L2BufferCache(*buffers);
	memoryType_ = V4L2_MEMORY_MMAP;

	return ret;
}

/**
 * \brief Export buffers from the video device
 * \param[in] count Number of buffers to allocate
 * \param[out] buffers Vector to store allocated buffers
 *
 * This function allocates \a count buffer from the video device and exports
 * them as dmabuf objects, stored in \a buffers. Unlike allocateBuffers(), this
 * function leaves the driver's internal buffer management uninitialized. The
 * video device shall be initialized with importBuffers() or allocateBuffers()
 * before it can accept queueBuffer() calls. The exported buffers are directly
 * usable with any V4L2 video device in DMABUF mode, or with other dmabuf
 * importers.
 *
 * The number of planes and their offsets and sizes are determined by the
 * currently active format on the device as set by setFormat(). They do not map
 * to the V4L2 buffer planes, but to colour planes of the pixel format. For
 * instance, if the active format is formats::NV12, the allocated FrameBuffer
 * instances will have two planes, for the luma and chroma components,
 * regardless of whether the device uses V4L2_PIX_FMT_NV12 or
 * V4L2_PIX_FMT_NV12M.
 *
 * Multiple independent sets of buffers can be allocated with multiple calls to
 * this function. Device-specific limitations may apply regarding the minimum
 * and maximum number of buffers per set, or to total amount of allocated
 * memory. The exported dmabuf lifetime is tied to the returned \a buffers. To
 * free a buffer, the caller shall delete the corresponding FrameBuffer
 * instance. No bookkeeping and automatic free is performed by the
 * V4L2VideoDevice class.
 *
 * If buffers have already been allocated with allocateBuffers() or imported
 * with importBuffers(), this function returns -EBUSY.
 *
 * \return The number of allocated buffers on success or a negative error code
 * otherwise
 * \retval -EBUSY buffers have already been allocated or imported
 */
int V4L2VideoDevice::exportBuffers(unsigned int count,
				   std::vector<std::unique_ptr<FrameBuffer>> *buffers)
{
	int ret = createBuffers(count, buffers);
	if (ret < 0)
		return ret;

	requestBuffers(0, V4L2_MEMORY_MMAP);

	return ret;
}

int V4L2VideoDevice::createBuffers(unsigned int count,
				   std::vector<std::unique_ptr<FrameBuffer>> *buffers)
{
	if (cache_) {
		LOG(V4L2, Error) << "Buffers already allocated";
		return -EINVAL;
	}

	int ret = requestBuffers(count, V4L2_MEMORY_MMAP);
	if (ret < 0)
		return ret;

	for (unsigned i = 0; i < count; ++i) {
		std::unique_ptr<FrameBuffer> buffer = createBuffer(i);
		if (!buffer) {
			LOG(V4L2, Error) << "Unable to create buffer";

			requestBuffers(0, V4L2_MEMORY_MMAP);
			buffers->clear();

			return -EINVAL;
		}

		buffers->push_back(std::move(buffer));
	}

	return count;
}

std::unique_ptr<FrameBuffer> V4L2VideoDevice::createBuffer(unsigned int index)
{
	struct v4l2_plane v4l2Planes[VIDEO_MAX_PLANES] = {};
	struct v4l2_buffer buf = {};

	buf.index = index;
	buf.type = bufferType_;
	buf.length = std::size(v4l2Planes);
	buf.m.planes = v4l2Planes;

	int ret = ioctl(VIDIOC_QUERYBUF, &buf);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Unable to query buffer " << index << ": "
			<< strerror(-ret);
		return nullptr;
	}

	const bool multiPlanar = V4L2_TYPE_IS_MULTIPLANAR(buf.type);
	const unsigned int numPlanes = multiPlanar ? buf.length : 1;

	if (numPlanes == 0 || numPlanes > VIDEO_MAX_PLANES) {
		LOG(V4L2, Error) << "Invalid number of planes";
		return nullptr;
	}

	std::vector<FrameBuffer::Plane> planes;
	for (unsigned int nplane = 0; nplane < numPlanes; nplane++) {
		UniqueFD fd = exportDmabufFd(buf.index, nplane);
		if (!fd.isValid())
			return nullptr;

		FrameBuffer::Plane plane;
		plane.fd = SharedFD(std::move(fd));
		/*
		 * V4L2 API doesn't provide dmabuf offset information of plane.
		 * Set 0 as a placeholder offset.
		 * \todo Set the right offset once V4L2 API provides a way.
		 */
		plane.offset = 0;
		plane.length = multiPlanar ? buf.m.planes[nplane].length : buf.length;

		planes.push_back(std::move(plane));
	}

	/*
	 * If we have a multi-planar format with a V4L2 single-planar buffer,
	 * split the single V4L2 plane into multiple FrameBuffer planes by
	 * computing the offsets manually.
	 *
	 * The format info is not guaranteed to be valid, as there are no
	 * PixelFormatInfo for metadata formats, so check it first.
	 */
	if (formatInfo_->isValid() && formatInfo_->numPlanes() != numPlanes) {
		/*
		 * There's no valid situation where the number of colour planes
		 * differs from the number of V4L2 planes and the V4L2 buffer
		 * has more than one plane.
		 */
		ASSERT(numPlanes == 1u);

		planes.resize(formatInfo_->numPlanes());
		const SharedFD &fd = planes[0].fd;
		size_t offset = 0;

		for (auto [i, plane] : utils::enumerate(planes)) {
			/*
			 * The stride is reported by V4L2 for the first plane
			 * only. Compute the stride of the other planes by
			 * taking the horizontal subsampling factor into
			 * account, which is equal to the bytesPerGroup ratio of
			 * the planes.
			 */
			unsigned int stride = format_.planes[0].bpl
					    * formatInfo_->planes[i].bytesPerGroup
					    / formatInfo_->planes[0].bytesPerGroup;

			plane.fd = fd;
			plane.offset = offset;
			plane.length = formatInfo_->planeSize(format_.size.height,
							      i, stride);
			offset += plane.length;
		}
	}

	return std::make_unique<FrameBuffer>(planes);
}

UniqueFD V4L2VideoDevice::exportDmabufFd(unsigned int index,
					 unsigned int plane)
{
	struct v4l2_exportbuffer expbuf = {};
	int ret;

	expbuf.type = bufferType_;
	expbuf.index = index;
	expbuf.plane = plane;
	expbuf.flags = O_RDWR;

	ret = ioctl(VIDIOC_EXPBUF, &expbuf);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Failed to export buffer: " << strerror(-ret);
		return {};
	}

	return UniqueFD(expbuf.fd);
}

/**
 * \brief Prepare the device to import \a count buffers
 * \param[in] count Number of buffers to prepare to import
 *
 * This function initializes the driver's buffer management to import buffers
 * in DMABUF mode. It requests buffers from the driver, but doesn't allocate
 * memory.
 *
 * Upon successful return, the video device is ready to accept queueBuffer()
 * calls. The buffers to be imported are provided to queueBuffer(), and may be
 * supplied externally, or come from a previous exportBuffers() call.
 *
 * Device initialization performed by this function shall later be cleaned up
 * with releaseBuffers(). If buffers have already been allocated with
 * allocateBuffers() or imported with importBuffers(), this function returns
 * -EBUSY.
 *
 * \return 0 on success or a negative error code otherwise
 * \retval -EBUSY buffers have already been allocated or imported
 */
int V4L2VideoDevice::importBuffers(unsigned int count)
{
	if (cache_) {
		LOG(V4L2, Error) << "Buffers already allocated";
		return -EINVAL;
	}

	memoryType_ = V4L2_MEMORY_DMABUF;

	int ret = requestBuffers(count, V4L2_MEMORY_DMABUF);
	if (ret)
		return ret;

	cache_ = new V4L2BufferCache(count);

	LOG(V4L2, Debug) << "Prepared to import " << count << " buffers";

	return 0;
}

/**
 * \brief Release resources allocated by allocateBuffers() or importBuffers()
 *
 * This function resets the driver's internal buffer management that was
 * initialized by a previous call to allocateBuffers() or importBuffers(). Any
 * memory allocated by allocateBuffers() is freed. Buffer exported by
 * exportBuffers(), if any, are not affected.
 */
int V4L2VideoDevice::releaseBuffers()
{
	LOG(V4L2, Debug) << "Releasing buffers";

	delete cache_;
	cache_ = nullptr;

	return requestBuffers(0, memoryType_);
}

/**
 * \brief Queue a buffer to the video device
 * \param[in] buffer The buffer to be queued
 *
 * For capture video devices the \a buffer will be filled with data by the
 * device. For output video devices the \a buffer shall contain valid data and
 * will be processed by the device. Once the device has finished processing the
 * buffer, it will be available for dequeue.
 *
 * The best available V4L2 buffer is picked for \a buffer using the V4L2 buffer
 * cache.
 *
 * Note that queueBuffer() will fail if the device is in the process of being
 * stopped from a streaming state through streamOff().
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::queueBuffer(FrameBuffer *buffer)
{
	struct v4l2_plane v4l2Planes[VIDEO_MAX_PLANES] = {};
	struct v4l2_buffer buf = {};
	int ret;

	if (state_ == State::Stopping) {
		LOG(V4L2, Error) << "Device is in a stopping state.";
		return -ESHUTDOWN;
	}

	/*
	 * Pipeline handlers should not requeue buffers after releasing the
	 * buffers on the device. Any occurence of this error should be fixed
	 * in the pipeline handler directly.
	 */
	if (!cache_) {
		LOG(V4L2, Fatal) << "No BufferCache available to queue.";
		return -ENOENT;
	}

	ret = cache_->get(*buffer);
	if (ret < 0)
		return ret;

	buf.index = ret;
	buf.type = bufferType_;
	buf.memory = memoryType_;
	buf.field = V4L2_FIELD_NONE;

	bool multiPlanar = V4L2_TYPE_IS_MULTIPLANAR(buf.type);
	const std::vector<FrameBuffer::Plane> &planes = buffer->planes();
	const unsigned int numV4l2Planes = format_.planesCount;

	/*
	 * Ensure that the frame buffer has enough planes, and that they're
	 * contiguous if the V4L2 format requires them to be.
	 */
	if (planes.size() < numV4l2Planes) {
		LOG(V4L2, Error) << "Frame buffer has too few planes";
		return -EINVAL;
	}

	if (planes.size() != numV4l2Planes && !buffer->_d()->isContiguous()) {
		LOG(V4L2, Error) << "Device format requires contiguous buffer";
		return -EINVAL;
	}

	if (buf.memory == V4L2_MEMORY_DMABUF) {
		if (multiPlanar) {
			for (unsigned int p = 0; p < numV4l2Planes; ++p)
				v4l2Planes[p].m.fd = planes[p].fd.get();
		} else {
			buf.m.fd = planes[0].fd.get();
		}
	}

	if (multiPlanar) {
		buf.length = numV4l2Planes;
		buf.m.planes = v4l2Planes;
	}

	if (V4L2_TYPE_IS_OUTPUT(buf.type)) {
		const FrameMetadata &metadata = buffer->metadata();

		if (numV4l2Planes != planes.size()) {
			/*
			 * If we have a multi-planar buffer with a V4L2
			 * single-planar format, coalesce all planes. The length
			 * and number of bytes used may only differ in the last
			 * plane as any other situation can't be represented.
			 */
			unsigned int bytesused = 0;
			unsigned int length = 0;

			for (auto [i, plane] : utils::enumerate(planes)) {
				bytesused += metadata.planes()[i].bytesused;
				length += plane.length;

				if (i != planes.size() - 1 && bytesused != length) {
					LOG(V4L2, Error)
						<< "Holes in multi-planar buffer not supported";
					return -EINVAL;
				}
			}

			if (multiPlanar) {
				v4l2Planes[0].bytesused = bytesused;
				v4l2Planes[0].length = length;
			} else {
				buf.bytesused = bytesused;
				buf.length = length;
			}
		} else if (multiPlanar) {
			/*
			 * If we use the multi-planar API, fill in the planes.
			 * The number of planes in the frame buffer and in the
			 * V4L2 buffer is guaranteed to be equal at this point.
			 */
			for (auto [i, plane] : utils::enumerate(planes)) {
				v4l2Planes[i].bytesused = metadata.planes()[i].bytesused;
				v4l2Planes[i].length = plane.length;
			}
		} else {
			/*
			 * Single-planar API with a single plane in the buffer
			 * is trivial to handle.
			 */
			buf.bytesused = metadata.planes()[0].bytesused;
			buf.length = planes[0].length;
		}

		/*
		 * Timestamps are to be supplied if the device is a mem-to-mem
		 * device. The drivers will have V4L2_BUF_FLAG_TIMESTAMP_COPY
		 * set hence these timestamps will be copied from the output
		 * buffers to capture buffers. If the device is not mem-to-mem,
		 * there is no harm in setting the timestamps as they will be
		 * ignored (and over-written).
		 */
		buf.timestamp.tv_sec = metadata.timestamp / 1000000000;
		buf.timestamp.tv_usec = (metadata.timestamp / 1000) % 1000000;
	}

	LOG(V4L2, Debug) << "Queueing buffer " << buf.index;

	ret = ioctl(VIDIOC_QBUF, &buf);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Failed to queue buffer " << buf.index << ": "
			<< strerror(-ret);
		return ret;
	}

	if (queuedBuffers_.empty()) {
		fdBufferNotifier_->setEnabled(true);
		if (watchdogDuration_)
			watchdog_.start(std::chrono::duration_cast<std::chrono::milliseconds>(watchdogDuration_));
	}

	queuedBuffers_[buf.index] = buffer;

	return 0;
}

/**
 * \brief Slot to handle completed buffer events from the V4L2 video device
 *
 * When this slot is called, a Buffer has become available from the device, and
 * will be emitted through the bufferReady Signal.
 *
 * For Capture video devices the FrameBuffer will contain valid data.
 * For Output video devices the FrameBuffer can be considered empty.
 */
void V4L2VideoDevice::bufferAvailable()
{
	FrameBuffer *buffer = dequeueBuffer();
	if (!buffer)
		return;

	/* Notify anyone listening to the device. */
	bufferReady.emit(buffer);
}

/**
 * \brief Dequeue the next available buffer from the video device
 *
 * This function dequeues the next available buffer from the device. If no
 * buffer is available to be dequeued it will return nullptr immediately.
 *
 * \return A pointer to the dequeued buffer on success, or nullptr otherwise
 */
FrameBuffer *V4L2VideoDevice::dequeueBuffer()
{
	struct v4l2_buffer buf = {};
	struct v4l2_plane planes[VIDEO_MAX_PLANES] = {};
	int ret;

	buf.type = bufferType_;
	buf.memory = memoryType_;

	bool multiPlanar = V4L2_TYPE_IS_MULTIPLANAR(buf.type);

	if (multiPlanar) {
		buf.length = VIDEO_MAX_PLANES;
		buf.m.planes = planes;
	}

	ret = ioctl(VIDIOC_DQBUF, &buf);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Failed to dequeue buffer: " << strerror(-ret);
		return nullptr;
	}

	LOG(V4L2, Debug) << "Dequeuing buffer " << buf.index;

	/*
	 * If the video node fails to stream-on successfully (which can occur
	 * when queuing a buffer), a vb2 kernel bug can lead to the buffer which
	 * returns a failure upon queuing being mistakenly kept in the kernel.
	 * This leads to the kernel notifying us that a buffer is available to
	 * dequeue, which we have no awareness of being queued, and thus we will
	 * not find it in the queuedBuffers_ list.
	 *
	 * Whilst this kernel bug has been fixed in mainline, ensure that we
	 * safely ignore buffers which are unexpected to prevent crashes on
	 * older kernels.
	 */
	auto it = queuedBuffers_.find(buf.index);
	if (it == queuedBuffers_.end()) {
		LOG(V4L2, Error)
			<< "Dequeued unexpected buffer index " << buf.index;

		return nullptr;
	}

	cache_->put(buf.index);

	FrameBuffer *buffer = it->second;
	queuedBuffers_.erase(it);

	if (queuedBuffers_.empty()) {
		fdBufferNotifier_->setEnabled(false);
		watchdog_.stop();
	} else if (watchdogDuration_) {
		/*
		 * Restart the watchdog timer if there are buffers still queued
		 * in the device.
		 */
		watchdog_.start(std::chrono::duration_cast<std::chrono::milliseconds>(watchdogDuration_));
	}

	buffer->metadata_.status = buf.flags & V4L2_BUF_FLAG_ERROR
				 ? FrameMetadata::FrameError
				 : FrameMetadata::FrameSuccess;
	buffer->metadata_.sequence = buf.sequence;
	buffer->metadata_.timestamp = buf.timestamp.tv_sec * 1000000000ULL
				    + buf.timestamp.tv_usec * 1000ULL;

	if (V4L2_TYPE_IS_OUTPUT(buf.type))
		return buffer;

	unsigned int numV4l2Planes = multiPlanar ? buf.length : 1;
	FrameMetadata &metadata = buffer->metadata_;

	if (numV4l2Planes != buffer->planes().size()) {
		/*
		 * If we have a multi-planar buffer with a V4L2
		 * single-planar format, split the V4L2 buffer across
		 * the buffer planes. Only the last plane may have less
		 * bytes used than its length.
		 */
		if (numV4l2Planes != 1) {
			LOG(V4L2, Error)
				<< "Invalid number of planes (" << numV4l2Planes
				<< " != " << buffer->planes().size() << ")";

			metadata.status = FrameMetadata::FrameError;
			return buffer;
		}

		/*
		 * With a V4L2 single-planar format, all the data is stored in
		 * a single memory plane. The number of bytes used is conveyed
		 * through that plane when using the V4L2 multi-planar API, or
		 * set directly in the buffer when using the V4L2 single-planar
		 * API.
		 */
		unsigned int bytesused = multiPlanar ? planes[0].bytesused
				       : buf.bytesused;
		unsigned int remaining = bytesused;

		for (auto [i, plane] : utils::enumerate(buffer->planes())) {
			if (!remaining) {
				LOG(V4L2, Error)
					<< "Dequeued buffer (" << bytesused
					<< " bytes) too small for plane lengths "
					<< utils::join(buffer->planes(), "/",
						       [](const FrameBuffer::Plane &p) {
							       return p.length;
						       });

				metadata.status = FrameMetadata::FrameError;
				return buffer;
			}

			metadata.planes()[i].bytesused =
				std::min(plane.length, remaining);
			remaining -= metadata.planes()[i].bytesused;
		}
	} else if (multiPlanar) {
		/*
		 * If we use the multi-planar API, fill in the planes.
		 * The number of planes in the frame buffer and in the
		 * V4L2 buffer is guaranteed to be equal at this point.
		 */
		for (unsigned int i = 0; i < numV4l2Planes; ++i)
			metadata.planes()[i].bytesused = planes[i].bytesused;
	} else {
		metadata.planes()[0].bytesused = buf.bytesused;
	}

	return buffer;
}

/**
 * \var V4L2VideoDevice::bufferReady
 * \brief A Signal emitted when a framebuffer completes
 */

/**
 * \brief Start the video stream
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::streamOn()
{
	int ret;

	ret = ioctl(VIDIOC_STREAMON, &bufferType_);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Failed to start streaming: " << strerror(-ret);
		return ret;
	}

	state_ = State::Streaming;
	if (watchdogDuration_ && !queuedBuffers_.empty())
		watchdog_.start(std::chrono::duration_cast<std::chrono::milliseconds>(watchdogDuration_));

	return 0;
}

/**
 * \brief Stop the video stream
 *
 * Buffers that are still queued when the video stream is stopped are
 * immediately dequeued with their status set to FrameMetadata::FrameCancelled,
 * and the bufferReady signal is emitted for them. The order in which those
 * buffers are dequeued is not specified.
 *
 * This will be a no-op if the stream is not started in the first place and
 * has no queued buffers.
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2VideoDevice::streamOff()
{
	int ret;

	if (state_ != State::Streaming && queuedBuffers_.empty())
		return 0;

	if (watchdogDuration_.count())
		watchdog_.stop();

	ret = ioctl(VIDIOC_STREAMOFF, &bufferType_);
	if (ret < 0) {
		LOG(V4L2, Error)
			<< "Failed to stop streaming: " << strerror(-ret);
		return ret;
	}

	state_ = State::Stopping;

	/* Send back all queued buffers. */
	for (auto it : queuedBuffers_) {
		FrameBuffer *buffer = it.second;

		cache_->put(it.first);
		buffer->metadata_.status = FrameMetadata::FrameCancelled;
		bufferReady.emit(buffer);
	}

	ASSERT(cache_->isEmpty());

	queuedBuffers_.clear();
	fdBufferNotifier_->setEnabled(false);
	state_ = State::Stopped;

	return 0;
}

/**
 * \brief Set the dequeue timeout value
 * \param[in] timeout The timeout value to be used
 *
 * Sets a timeout value, given by \a timeout, that will be used by a watchdog
 * timer to ensure buffer dequeue events are periodically occurring when the
 * device is streaming. The watchdog timer is only active when the device is
 * streaming, so it is not necessary to disable it when the device stops
 * streaming. The timeout value can be safely updated at any time.
 *
 * If the timer expires, the \ref V4L2VideoDevice::dequeueTimeout signal is
 * emitted. This can typically be used by pipeline handlers to be notified of
 * stalled devices.
 *
 * Set \a timeout to 0 to disable the watchdog timer.
 */
void V4L2VideoDevice::setDequeueTimeout(utils::Duration timeout)
{
	watchdogDuration_ = timeout;

	watchdog_.stop();
	if (watchdogDuration_ && state_ == State::Streaming && !queuedBuffers_.empty())
		watchdog_.start(std::chrono::duration_cast<std::chrono::milliseconds>(timeout));
}

/**
 * \var V4L2VideoDevice::dequeueTimeout
 * \brief A Signal emitted when the dequeue watchdog timer expires
 */

/**
 * \brief Slot to handle an expired dequeue timer
 *
 * When this slot is called, the time between successive dequeue events is over
 * the required timeout. Emit the \ref V4L2VideoDevice::dequeueTimeout signal.
 */
void V4L2VideoDevice::watchdogExpired()
{
	LOG(V4L2, Warning)
		<< "Dequeue timer of " << watchdogDuration_ << " has expired!";

	dequeueTimeout.emit();
}

/**
 * \brief Create a new video device instance from \a entity in media device
 * \a media
 * \param[in] media The media device where the entity is registered
 * \param[in] entity The media entity name
 *
 * \return A newly created V4L2VideoDevice on success, nullptr otherwise
 */
std::unique_ptr<V4L2VideoDevice>
V4L2VideoDevice::fromEntityName(const MediaDevice *media,
				const std::string &entity)
{
	MediaEntity *mediaEntity = media->getEntityByName(entity);
	if (!mediaEntity)
		return nullptr;

	return std::make_unique<V4L2VideoDevice>(mediaEntity);
}

/**
 * \class V4L2M2MDevice
 * \brief Memory-to-Memory video device
 *
 * The V4L2M2MDevice manages two V4L2VideoDevice instances on the same
 * deviceNode which operate together using two queues to implement the V4L2
 * Memory to Memory API.
 *
 * The two devices should be opened by calling open() on the V4L2M2MDevice, and
 * can be closed by calling close on the V4L2M2MDevice.
 *
 * Calling V4L2VideoDevice::open() and V4L2VideoDevice::close() on the capture
 * or output V4L2VideoDevice is not permitted.
 */

/**
 * \fn V4L2M2MDevice::output
 * \brief Retrieve the output V4L2VideoDevice instance
 * \return The output V4L2VideoDevice instance
 */

/**
 * \fn V4L2M2MDevice::capture
 * \brief Retrieve the capture V4L2VideoDevice instance
 * \return The capture V4L2VideoDevice instance
 */

/**
 * \brief Create a new V4L2M2MDevice from the \a deviceNode
 * \param[in] deviceNode The file-system path to the video device node
 */
V4L2M2MDevice::V4L2M2MDevice(const std::string &deviceNode)
	: deviceNode_(deviceNode)
{
	output_ = new V4L2VideoDevice(deviceNode);
	capture_ = new V4L2VideoDevice(deviceNode);
}

V4L2M2MDevice::~V4L2M2MDevice()
{
	delete capture_;
	delete output_;
}

/**
 * \brief Open a V4L2 Memory to Memory device
 *
 * Open the device node and prepare the two V4L2VideoDevice instances to handle
 * their respective buffer queues.
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2M2MDevice::open()
{
	int ret;

	/*
	 * The output and capture V4L2VideoDevice instances use the same file
	 * handle for the same device node.
	 */
	SharedFD fd(syscall(SYS_openat, AT_FDCWD, deviceNode_.c_str(),
			    O_RDWR | O_NONBLOCK));
	if (!fd.isValid()) {
		ret = -errno;
		LOG(V4L2, Error) << "Failed to open V4L2 M2M device: "
				 << strerror(-ret);
		return ret;
	}

	ret = output_->open(fd, V4L2_BUF_TYPE_VIDEO_OUTPUT);
	if (ret)
		goto err;

	ret = capture_->open(fd, V4L2_BUF_TYPE_VIDEO_CAPTURE);
	if (ret)
		goto err;

	return 0;

err:
	close();

	return ret;
}

/**
 * \brief Close the memory-to-memory device, releasing any resources acquired by
 * open()
 */
void V4L2M2MDevice::close()
{
	capture_->close();
	output_->close();
}

} /* namespace libcamera */