summaryrefslogtreecommitdiff
path: root/src/libcamera/v4l2_device.cpp
blob: ccc5fbfc2268a5b6b0ec08640563d0b7e853174a (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
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * v4l2_device.cpp - V4L2 Device
 */

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

#include <libcamera/buffer.h>
#include <libcamera/event_notifier.h>

#include "log.h"
#include "media_device.h"
#include "media_object.h"
#include "v4l2_device.h"

/**
 * \file v4l2_device.h
 * \brief V4L2 Device API
 */
namespace libcamera {

LOG_DEFINE_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 device card name
 * \return The string containing the device name
 */

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

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

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

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

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

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

/**
 * \fn V4L2Capability::isMeta()
 * \brief Identify if the device captures or outputs image meta-data
 *
 * \todo Add support for META_CAPTURE introduced in Linux v5.0
 *
 * \return True if the device can capture or output image meta-data
 */

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

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

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

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

/**
 * \class V4L2DeviceFormat
 * \brief The V4L2 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 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 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 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.
 */

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

/**
 * \var V4L2DeviceFormat::height
 * \brief The image height 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::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.fill(0);
	ss << width << "x" << height << "-0x" << std::hex
	   << std::setw(8) << fourcc;

	return ss.str();
}

/**
 * \class V4L2Device
 * \brief V4L2Device object and API
 *
 * The V4L2 Device API class models an instance of a V4L2 device node.
 * 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 device capabilities are validated when the device is opened and the
 * device is rejected if it is not a suitable V4L2 capture or output device, or
 * if the 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 V4L2Device 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.
 */

/**
 * \brief Construct a V4L2Device
 * \param[in] deviceNode The file-system path to the video device node
 */
V4L2Device::V4L2Device(const std::string &deviceNode)
	: deviceNode_(deviceNode), fd_(-1), bufferPool_(nullptr),
	  queuedBuffersCount_(0), fdEvent_(nullptr)
{
	/*
	 * We default to an MMAP based CAPTURE 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 V4L2Device from a MediaEntity
 * \param[in] entity The MediaEntity to build the device from
 *
 * Construct a V4L2Device from a MediaEntity's device node path.
 */
V4L2Device::V4L2Device(const MediaEntity *entity)
	: V4L2Device(entity->deviceNode())
{
}

V4L2Device::~V4L2Device()
{
	close();
}

/**
 * \brief Open a V4L2 device and query its capabilities
 * \return 0 on success or a negative error code otherwise
 */
int V4L2Device::open()
{
	int ret;

	if (isOpen()) {
		LOG(V4L2, Error) << "Device already open";
		return -EBUSY;
	}

	ret = ::open(deviceNode_.c_str(), O_RDWR | O_NONBLOCK);
	if (ret < 0) {
		ret = -errno;
		LOG(V4L2, Error)
			<< "Failed to open V4L2 device: " << strerror(-ret);
		return ret;
	}
	fd_ = ret;

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

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

	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 devices
	 * (POLLIN), and write notifications for OUTPUT devices (POLLOUT).
	 */
	if (caps_.isVideoCapture()) {
		fdEvent_ = new EventNotifier(fd_, EventNotifier::Read);
		bufferType_ = caps_.isMultiplanar()
			    ? V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
			    : V4L2_BUF_TYPE_VIDEO_CAPTURE;
	} else if (caps_.isVideoOutput()) {
		fdEvent_ = new EventNotifier(fd_, EventNotifier::Write);
		bufferType_ = caps_.isMultiplanar()
			    ? V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE
			    : V4L2_BUF_TYPE_VIDEO_OUTPUT;
	} else if (caps_.isMetaCapture()) {
		fdEvent_ = new EventNotifier(fd_, EventNotifier::Read);
		bufferType_ = V4L2_BUF_TYPE_META_CAPTURE;
	} else {
		LOG(V4L2, Debug) << "Device is not a supported type";
		return -EINVAL;
	}

	fdEvent_->activated.connect(this, &V4L2Device::bufferAvailable);
	fdEvent_->setEnabled(false);

	return 0;
}

/**
 * \brief Check if device is successfully opened
 * \return True if the device is open, false otherwise
 */
bool V4L2Device::isOpen() const
{
	return fd_ != -1;
}

/**
 * \brief Close the device, releasing any resources acquired by open()
 */
void V4L2Device::close()
{
	if (fd_ < 0)
		return;

	releaseBuffers();
	delete fdEvent_;

	::close(fd_);
	fd_ = -1;
}

/**
 * \fn V4L2Device::driverName()
 * \brief Retrieve the name of the V4L2 device driver
 * \return The string containing the driver name
 */

/**
 * \fn V4L2Device::deviceName()
 * \brief Retrieve the name of the V4L2 device
 * \return The string containing the device name
 */

/**
 * \fn V4L2Device::busName()
 * \brief Retrieve the location of the device in the system
 * \return The string containing the device location
 */

/**
 * \fn V4L2Device::deviceNode()
 * \brief Retrieve the video device node path
 * \return The video device device node path
 */

std::string V4L2Device::logPrefix() const
{
	return deviceNode_;
}

/**
 * \brief Retrieve the image format set on the V4L2 device
 * \param[out] format The image format applied on the device
 * \return 0 on success or a negative error code otherwise
 */
int V4L2Device::getFormat(V4L2DeviceFormat *format)
{
	return caps_.isMultiplanar() ? getFormatMultiplane(format) :
				       getFormatSingleplane(format);
}

/**
 * \brief Configure an image format on the V4L2 device
 * \param[inout] format The image format to apply to the device
 *
 * Apply the supplied \a format to the device, and return the actually
 * applied format parameters, as \ref V4L2Device::getFormat would do.
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2Device::setFormat(V4L2DeviceFormat *format)
{
	return caps_.isMultiplanar() ? setFormatMultiplane(format) :
				       setFormatSingleplane(format);
}

int V4L2Device::getFormatSingleplane(V4L2DeviceFormat *format)
{
	struct v4l2_format v4l2Format = {};
	struct v4l2_pix_format *pix = &v4l2Format.fmt.pix;
	int ret;

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

	format->width = pix->width;
	format->height = pix->height;
	format->fourcc = pix->pixelformat;
	format->planesCount = 1;
	format->planes[0].bpl = pix->bytesperline;
	format->planes[0].size = pix->sizeimage;

	return 0;
}

int V4L2Device::setFormatSingleplane(V4L2DeviceFormat *format)
{
	struct v4l2_format v4l2Format = {};
	struct v4l2_pix_format *pix = &v4l2Format.fmt.pix;
	int ret;

	v4l2Format.type = bufferType_;
	pix->width = format->width;
	pix->height = format->height;
	pix->pixelformat = format->fourcc;
	pix->bytesperline = format->planes[0].bpl;
	pix->field = V4L2_FIELD_NONE;

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

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

	return 0;
}

int V4L2Device::getFormatMultiplane(V4L2DeviceFormat *format)
{
	struct v4l2_format v4l2Format = {};
	struct v4l2_pix_format_mplane *pix = &v4l2Format.fmt.pix_mp;
	int ret;

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

	format->width = pix->width;
	format->height = pix->height;
	format->fourcc = 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;
	}

	return 0;
}

int V4L2Device::setFormatMultiplane(V4L2DeviceFormat *format)
{
	struct v4l2_format v4l2Format = {};
	struct v4l2_pix_format_mplane *pix = &v4l2Format.fmt.pix_mp;
	int ret;

	v4l2Format.type = bufferType_;
	pix->width = format->width;
	pix->height = format->height;
	pix->pixelformat = format->fourcc;
	pix->num_planes = format->planesCount;
	pix->field = V4L2_FIELD_NONE;

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

	/*
	 * Return to caller the format actually applied on the device,
	 * which might differ from the requested one.
	 */
	format->width = pix->width;
	format->height = pix->height;
	format->fourcc = 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;
	}

	return 0;
}

int V4L2Device::requestBuffers(unsigned int count)
{
	struct v4l2_requestbuffers rb = {};
	int ret;

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

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

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

	return rb.count;
}

/**
 * \brief Request buffers to be allocated from the device and stored in the
 *  buffer pool provided.
 * \param[out] pool BufferPool to populate with buffers
 * \return 0 on success or a negative error code otherwise
 */
int V4L2Device::exportBuffers(BufferPool *pool)
{
	unsigned int allocatedBuffers;
	unsigned int i;
	int ret;

	memoryType_ = V4L2_MEMORY_MMAP;

	ret = requestBuffers(pool->count());
	if (ret < 0)
		return ret;

	allocatedBuffers = ret;
	if (allocatedBuffers < pool->count()) {
		LOG(V4L2, Error) << "Not enough buffers provided by V4L2Device";
		requestBuffers(0);
		return -ENOMEM;
	}

	/* Map the buffers. */
	for (i = 0; i < pool->count(); ++i) {
		struct v4l2_plane planes[VIDEO_MAX_PLANES] = {};
		struct v4l2_buffer buf = {};
		struct Buffer &buffer = pool->buffers()[i];

		buf.index = i;
		buf.type = bufferType_;
		buf.memory = memoryType_;
		buf.length = VIDEO_MAX_PLANES;
		buf.m.planes = planes;

		ret = ioctl(fd_, VIDIOC_QUERYBUF, &buf);
		if (ret < 0) {
			ret = -errno;
			LOG(V4L2, Error)
				<< "Unable to query buffer " << i << ": "
				<< strerror(-ret);
			break;
		}

		if (V4L2_TYPE_IS_MULTIPLANAR(buf.type)) {
			for (unsigned int p = 0; p < buf.length; ++p) {
				ret = createPlane(&buffer, p,
						  buf.m.planes[p].length);
				if (ret)
					break;
			}
		} else {
			ret = createPlane(&buffer, 0, buf.length);
		}

		if (ret) {
			LOG(V4L2, Error) << "Failed to create plane";
			break;
		}
	}

	if (ret) {
		requestBuffers(0);
		pool->destroyBuffers();
		return ret;
	}

	bufferPool_ = pool;

	return 0;
}

int V4L2Device::createPlane(Buffer *buffer, unsigned int planeIndex,
			    unsigned int length)
{
	struct v4l2_exportbuffer expbuf = {};
	int ret;

	LOG(V4L2, Debug)
		<< "Buffer " << buffer->index()
		<< " plane " << planeIndex
		<< ": length=" << length;

	expbuf.type = bufferType_;
	expbuf.index = buffer->index();
	expbuf.plane = planeIndex;
	expbuf.flags = O_RDWR;

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

	buffer->planes().emplace_back();
	Plane &plane = buffer->planes().back();
	plane.setDmabuf(expbuf.fd, length);
	::close(expbuf.fd);

	return 0;
}

/**
 * \brief Import the externally allocated \a pool of buffers
 * \param[in] pool BufferPool of buffers to import
 * \return 0 on success or a negative error code otherwise
 */
int V4L2Device::importBuffers(BufferPool *pool)
{
	unsigned int allocatedBuffers;
	int ret;

	memoryType_ = V4L2_MEMORY_DMABUF;

	ret = requestBuffers(pool->count());
	if (ret < 0)
		return ret;

	allocatedBuffers = ret;
	if (allocatedBuffers < pool->count()) {
		LOG(V4L2, Error)
			<< "Not enough buffers provided by V4L2Device";
		requestBuffers(0);
		return -ENOMEM;
	}

	LOG(V4L2, Debug) << "provided pool of " << pool->count() << "buffers";
	bufferPool_ = pool;

	return 0;
}

/**
 * \brief Release all internally allocated buffers
 */
int V4L2Device::releaseBuffers()
{
	LOG(V4L2, Debug) << "Releasing bufferPool";

	bufferPool_ = nullptr;

	return requestBuffers(0);
}

/**
 * \brief Queue a buffer into the device
 * \param[in] buffer The buffer to be queued
 *
 * For capture devices the \a buffer will be filled with data by the device.
 * For output 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.
 *
 * \todo Support output devices (bytesused, ...)
 * \todo Support imported buffers (dmabuf fd)
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2Device::queueBuffer(Buffer *buffer)
{
	struct v4l2_buffer buf = {};
	struct v4l2_plane planes[VIDEO_MAX_PLANES] = {};
	int ret;

	buf.index = buffer->index();
	buf.type = bufferType_;
	buf.memory = memoryType_;
	buf.field = V4L2_FIELD_NONE;

	bool multiPlanar = V4L2_TYPE_IS_MULTIPLANAR(buf.type);

	if (buf.memory == V4L2_MEMORY_DMABUF) {
		if (multiPlanar) {
			for (unsigned int p = 0;
			     p < buffer->planes().size();
			     p++)
				planes[p].m.fd = buffer->planes()[p].dmabuf();
		} else {
			buf.m.fd = buffer->planes()[0].dmabuf();
		}
	}

	if (multiPlanar) {
		buf.length = buffer->planes().size();
		buf.m.planes = planes;
	}

	if (V4L2_TYPE_IS_OUTPUT(bufferType_)) {
		buf.bytesused = buffer->bytesused_;
		buf.sequence = buffer->sequence_;
		buf.timestamp.tv_sec = buffer->timestamp_ / 1000000000;
		buf.timestamp.tv_usec = (buffer->timestamp_ / 1000) % 1000000;
	}

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

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

	if (queuedBuffersCount_++ == 0)
		fdEvent_->setEnabled(true);

	return 0;
}

/**
 * \brief Dequeue the next available buffer from the device
 *
 * This method 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
 */
Buffer *V4L2Device::dequeueBuffer()
{
	struct v4l2_buffer buf = {};
	struct v4l2_plane planes[VIDEO_MAX_PLANES] = {};
	int ret;

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

	if (V4L2_TYPE_IS_MULTIPLANAR(buf.type)) {
		buf.length = VIDEO_MAX_PLANES;
		buf.m.planes = planes;
	}

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

	ASSERT(buf.index < bufferPool_->count());

	if (--queuedBuffersCount_ == 0)
		fdEvent_->setEnabled(false);

	Buffer *buffer = &bufferPool_->buffers()[buf.index];

	buffer->bytesused_ = buf.bytesused;
	buffer->timestamp_ = buf.timestamp.tv_sec * 1000000000ULL
			   + buf.timestamp.tv_usec * 1000ULL;
	buffer->sequence_ = buf.sequence;
	buffer->status_ = buf.flags & V4L2_BUF_FLAG_ERROR
			? Buffer::BufferError : Buffer::BufferSuccess;

	return buffer;
}

/**
 * \brief Slot to handle completed buffer events from the V4L2 device
 * \param[in] notifier The event notifier
 *
 * When this slot is called, a Buffer has become available from the device, and
 * will be emitted through the bufferReady Signal.
 *
 * For Capture devices the Buffer will contain valid data.
 * For Output devices the Buffer can be considered empty.
 */
void V4L2Device::bufferAvailable(EventNotifier *notifier)
{
	Buffer *buffer = dequeueBuffer();
	if (!buffer)
		return;

	LOG(V4L2, Debug) << "Buffer " << buffer->index() << " is available";

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

/**
 * \var V4L2Device::bufferReady
 * \brief A Signal emitted when a buffer completes
 */

/**
 * \brief Start the video stream
 * \return 0 on success or a negative error code otherwise
 */
int V4L2Device::streamOn()
{
	int ret;

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

	return 0;
}

/**
 * \brief Stop the video stream
 *
 * \todo Ensure completion notifications are sent for all queued buffers
 *
 * \return 0 on success or a negative error code otherwise
 */
int V4L2Device::streamOff()
{
	int ret;

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

	queuedBuffersCount_ = 0;
	fdEvent_->setEnabled(false);

	return 0;
}

/**
 * \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
 *
 * Releasing memory of the newly created instance is responsibility of the
 * caller of this function.
 *
 * \return A newly created V4L2Device on success, nullptr otherwise
 */
V4L2Device *V4L2Device::fromEntityName(const MediaDevice *media,
				       const std::string &entity)
{
	MediaEntity *mediaEntity = media->getEntityByName(entity);
	if (!mediaEntity)
		return nullptr;

	return new V4L2Device(mediaEntity);
}

} /* namespace libcamera */