vda/v4l2_device.cc - platform/external/v4l2_codec2 - Git at Google

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 // Note: ported from Chromium commit head: 09ea0d2
 // Note: it's also merged with generic_v4l2_device.cc (head: a9d98e6)

 #include <errno.h>
 #include <fcntl.h>
 #include <poll.h>
 #include <string.h>
 #include <sys/eventfd.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>

 #include "base/numerics/safe_conversions.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/strings/stringprintf.h"
 #include "v4l2_device.h"

 #define DVLOGF(level) DVLOG(level) << __func__ << "(): "
 #define VLOGF(level) VLOG(level) << __func__ << "(): "
 #define VPLOGF(level) VPLOG(level) << __func__ << "(): "

 namespace media {

 V4L2Device::V4L2Device() {}

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

 // static
 VideoPixelFormat V4L2Device::V4L2PixFmtToVideoPixelFormat(uint32_t pix_fmt) {
   switch (pix_fmt) {
     case V4L2_PIX_FMT_NV12:
     case V4L2_PIX_FMT_NV12M:
       return PIXEL_FORMAT_NV12;

     case V4L2_PIX_FMT_MT21:
       return PIXEL_FORMAT_MT21;

     case V4L2_PIX_FMT_YUV420:
     case V4L2_PIX_FMT_YUV420M:
       return PIXEL_FORMAT_I420;

     case V4L2_PIX_FMT_YVU420:
       return PIXEL_FORMAT_YV12;

     case V4L2_PIX_FMT_YUV422M:
       return PIXEL_FORMAT_I422;

     case V4L2_PIX_FMT_RGB32:
       return PIXEL_FORMAT_ARGB;

     default:
       DVLOGF(1) << "Add more cases as needed";
       return PIXEL_FORMAT_UNKNOWN;
   }
 }

 // static
 uint32_t V4L2Device::VideoPixelFormatToV4L2PixFmt(VideoPixelFormat format) {
   switch (format) {
     case PIXEL_FORMAT_NV12:
       return V4L2_PIX_FMT_NV12M;

     case PIXEL_FORMAT_MT21:
       return V4L2_PIX_FMT_MT21;

     case PIXEL_FORMAT_I420:
       return V4L2_PIX_FMT_YUV420M;

     case PIXEL_FORMAT_YV12:
       return V4L2_PIX_FMT_YVU420;

     default:
       LOG(FATAL) << "Add more cases as needed";
       return 0;
   }
 }

 // static
 uint32_t V4L2Device::VideoCodecProfileToV4L2PixFmt(VideoCodecProfile profile,
                                                    bool slice_based) {
   if (profile >= H264PROFILE_MIN && profile <= H264PROFILE_MAX) {
     if (slice_based)
       return V4L2_PIX_FMT_H264_SLICE;
     else
       return V4L2_PIX_FMT_H264;
   } else if (profile >= VP8PROFILE_MIN && profile <= VP8PROFILE_MAX) {
     if (slice_based)
       return V4L2_PIX_FMT_VP8_FRAME;
     else
       return V4L2_PIX_FMT_VP8;
   } else if (profile >= VP9PROFILE_MIN && profile <= VP9PROFILE_MAX) {
     if (slice_based)
       return V4L2_PIX_FMT_VP9_FRAME;
     else
       return V4L2_PIX_FMT_VP9;
   } else {
     LOG(FATAL) << "Add more cases as needed";
     return 0;
   }
 }

 // static
 std::vector<VideoCodecProfile> V4L2Device::V4L2PixFmtToVideoCodecProfiles(
     uint32_t pix_fmt,
     bool is_encoder) {
   VideoCodecProfile min_profile, max_profile;
   std::vector<VideoCodecProfile> profiles;

   switch (pix_fmt) {
     case V4L2_PIX_FMT_H264:
     case V4L2_PIX_FMT_H264_SLICE:
       if (is_encoder) {
         // TODO(posciak): need to query the device for supported H.264 profiles,
         // for now choose Main as a sensible default.
         min_profile = H264PROFILE_MAIN;
         max_profile = H264PROFILE_MAIN;
       } else {
         min_profile = H264PROFILE_MIN;
         max_profile = H264PROFILE_MAX;
       }
       break;

     case V4L2_PIX_FMT_VP8:
     case V4L2_PIX_FMT_VP8_FRAME:
       min_profile = VP8PROFILE_MIN;
       max_profile = VP8PROFILE_MAX;
       break;

     case V4L2_PIX_FMT_VP9:
     case V4L2_PIX_FMT_VP9_FRAME:
       min_profile = VP9PROFILE_MIN;
       max_profile = VP9PROFILE_MAX;
       break;

     default:
       VLOGF(1) << "Unhandled pixelformat " << std::hex << "0x" << pix_fmt;
       return profiles;
   }

   for (int profile = min_profile; profile <= max_profile; ++profile)
     profiles.push_back(static_cast<VideoCodecProfile>(profile));

   return profiles;
 }

 int V4L2Device::Ioctl(int request, void* arg) {
   DCHECK(device_fd_.is_valid());
   return HANDLE_EINTR(ioctl(device_fd_.get(), request, arg));
 }

 bool V4L2Device::Poll(bool poll_device, bool* event_pending) {
   struct pollfd pollfds[2];
   nfds_t nfds;
   int pollfd = -1;

   pollfds[0].fd = device_poll_interrupt_fd_.get();
   pollfds[0].events = POLLIN | POLLERR;
   nfds = 1;

   if (poll_device) {
     DVLOGF(5) << "Poll(): adding device fd to poll() set";
     pollfds[nfds].fd = device_fd_.get();
     pollfds[nfds].events = POLLIN | POLLOUT | POLLERR | POLLPRI;
     pollfd = nfds;
     nfds++;
   }

   if (HANDLE_EINTR(poll(pollfds, nfds, -1)) == -1) {
     VPLOGF(1) << "poll() failed";
     return false;
   }
   *event_pending = (pollfd != -1 && pollfds[pollfd].revents & POLLPRI);
   return true;
 }

 void* V4L2Device::Mmap(void* addr,
                        unsigned int len,
                        int prot,
                        int flags,
                        unsigned int offset) {
   DCHECK(device_fd_.is_valid());
   return mmap(addr, len, prot, flags, device_fd_.get(), offset);
 }

 void V4L2Device::Munmap(void* addr, unsigned int len) {
   munmap(addr, len);
 }

 bool V4L2Device::SetDevicePollInterrupt() {
   DVLOGF(4);

   const uint64_t buf = 1;
   if (HANDLE_EINTR(write(device_poll_interrupt_fd_.get(), &buf, sizeof(buf))) ==
       -1) {
     VPLOGF(1) << "write() failed";
     return false;
   }
   return true;
 }

 bool V4L2Device::ClearDevicePollInterrupt() {
   DVLOGF(5);

   uint64_t buf;
   if (HANDLE_EINTR(read(device_poll_interrupt_fd_.get(), &buf, sizeof(buf))) ==
       -1) {
     if (errno == EAGAIN) {
       // No interrupt flag set, and we're reading nonblocking.  Not an error.
       return true;
     } else {
       VPLOGF(1) << "read() failed";
       return false;
     }
   }
   return true;
 }

 bool V4L2Device::Open(Type type, uint32_t v4l2_pixfmt) {
   VLOGF(2);
   std::string path = GetDevicePathFor(type, v4l2_pixfmt);

   if (path.empty()) {
     VLOGF(1) << "No devices supporting " << std::hex << "0x" << v4l2_pixfmt
              << " for type: " << static_cast<int>(type);
     return false;
   }

   if (!OpenDevicePath(path, type)) {
     VLOGF(1) << "Failed opening " << path;
     return false;
   }

   device_poll_interrupt_fd_.reset(eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC));
   if (!device_poll_interrupt_fd_.is_valid()) {
     VLOGF(1) << "Failed creating a poll interrupt fd";
     return false;
   }

   return true;
 }

 std::vector<base::ScopedFD> V4L2Device::GetDmabufsForV4L2Buffer(
     int index,
     size_t num_planes,
     enum v4l2_buf_type buf_type) {
   VLOGF(2);
   DCHECK(V4L2_TYPE_IS_MULTIPLANAR(buf_type));

   std::vector<base::ScopedFD> dmabuf_fds;
   for (size_t i = 0; i < num_planes; ++i) {
     struct v4l2_exportbuffer expbuf;
     memset(&expbuf, 0, sizeof(expbuf));
     expbuf.type = buf_type;
     expbuf.index = index;
     expbuf.plane = i;
     expbuf.flags = O_CLOEXEC;
     if (Ioctl(VIDIOC_EXPBUF, &expbuf) != 0) {
       dmabuf_fds.clear();
       break;
     }

     dmabuf_fds.push_back(base::ScopedFD(expbuf.fd));
   }

   return dmabuf_fds;
 }

 VideoDecodeAccelerator::SupportedProfiles
 V4L2Device::GetSupportedDecodeProfiles(const size_t num_formats,
                                        const uint32_t pixelformats[]) {
   VideoDecodeAccelerator::SupportedProfiles supported_profiles;

   Type type = Type::kDecoder;
   const auto& devices = GetDevicesForType(type);
   for (const auto& device : devices) {
     if (!OpenDevicePath(device.first, type)) {
       VLOGF(1) << "Failed opening " << device.first;
       continue;
     }

     const auto& profiles =
         EnumerateSupportedDecodeProfiles(num_formats, pixelformats);
     supported_profiles.insert(supported_profiles.end(), profiles.begin(),
                               profiles.end());
     CloseDevice();
   }

   return supported_profiles;
 }

 void V4L2Device::GetSupportedResolution(uint32_t pixelformat,
                                         Size* min_resolution,
                                         Size* max_resolution) {
   max_resolution->SetSize(0, 0);
   min_resolution->SetSize(0, 0);
   v4l2_frmsizeenum frame_size;
   memset(&frame_size, 0, sizeof(frame_size));
   frame_size.pixel_format = pixelformat;
   for (; Ioctl(VIDIOC_ENUM_FRAMESIZES, &frame_size) == 0; ++frame_size.index) {
     if (frame_size.type == V4L2_FRMSIZE_TYPE_DISCRETE) {
       if (frame_size.discrete.width >=
               base::checked_cast<uint32_t>(max_resolution->width()) &&
           frame_size.discrete.height >=
               base::checked_cast<uint32_t>(max_resolution->height())) {
         max_resolution->SetSize(frame_size.discrete.width,
                                 frame_size.discrete.height);
       }
       if (min_resolution->IsEmpty() ||
           (frame_size.discrete.width <=
                base::checked_cast<uint32_t>(min_resolution->width()) &&
            frame_size.discrete.height <=
                base::checked_cast<uint32_t>(min_resolution->height()))) {
         min_resolution->SetSize(frame_size.discrete.width,
                                 frame_size.discrete.height);
       }
     } else if (frame_size.type == V4L2_FRMSIZE_TYPE_STEPWISE ||
                frame_size.type == V4L2_FRMSIZE_TYPE_CONTINUOUS) {
       max_resolution->SetSize(frame_size.stepwise.max_width,
                               frame_size.stepwise.max_height);
       min_resolution->SetSize(frame_size.stepwise.min_width,
                               frame_size.stepwise.min_height);
       break;
     }
   }
   if (max_resolution->IsEmpty()) {
     max_resolution->SetSize(1920, 1088);
     VLOGF(1) << "GetSupportedResolution failed to get maximum resolution for "
              << "fourcc " << std::hex << pixelformat
              << ", fall back to " << max_resolution->ToString();
   }
   if (min_resolution->IsEmpty()) {
     min_resolution->SetSize(16, 16);
     VLOGF(1) << "GetSupportedResolution failed to get minimum resolution for "
              << "fourcc " << std::hex << pixelformat
              << ", fall back to " << min_resolution->ToString();
   }
 }

 std::vector<uint32_t> V4L2Device::EnumerateSupportedPixelformats(
     v4l2_buf_type buf_type) {
   std::vector<uint32_t> pixelformats;

   v4l2_fmtdesc fmtdesc;
   memset(&fmtdesc, 0, sizeof(fmtdesc));
   fmtdesc.type = buf_type;

   for (; Ioctl(VIDIOC_ENUM_FMT, &fmtdesc) == 0; ++fmtdesc.index) {
     DVLOGF(3) << "Found " << fmtdesc.description << std::hex << " (0x"
               << fmtdesc.pixelformat << ")";
     pixelformats.push_back(fmtdesc.pixelformat);
   }

   return pixelformats;
 }

 VideoDecodeAccelerator::SupportedProfiles
 V4L2Device::EnumerateSupportedDecodeProfiles(const size_t num_formats,
                                              const uint32_t pixelformats[]) {
   VideoDecodeAccelerator::SupportedProfiles profiles;

   const auto& supported_pixelformats =
       EnumerateSupportedPixelformats(V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE);

   for (uint32_t pixelformat : supported_pixelformats) {
     if (std::find(pixelformats, pixelformats + num_formats, pixelformat) ==
         pixelformats + num_formats)
       continue;

     VideoDecodeAccelerator::SupportedProfile profile;
     GetSupportedResolution(pixelformat, &profile.min_resolution,
                            &profile.max_resolution);

     const auto video_codec_profiles =
         V4L2PixFmtToVideoCodecProfiles(pixelformat, false);

     for (const auto& video_codec_profile : video_codec_profiles) {
       profile.profile = video_codec_profile;
       profiles.push_back(profile);

       DVLOGF(3) << "Found decoder profile " << GetProfileName(profile.profile)
                 << ", resolutions: " << profile.min_resolution.ToString() << " "
                 << profile.max_resolution.ToString();
     }
   }

   return profiles;
 }

 bool V4L2Device::OpenDevicePath(const std::string& path, Type type) {
   DCHECK(!device_fd_.is_valid());

   device_fd_.reset(
       HANDLE_EINTR(open(path.c_str(), O_RDWR | O_NONBLOCK | O_CLOEXEC)));
   if (!device_fd_.is_valid())
     return false;

   return true;
 }

 void V4L2Device::CloseDevice() {
   VLOGF(2);
   device_fd_.reset();
 }

 void V4L2Device::EnumerateDevicesForType(Type type) {
   static const std::string kDecoderDevicePattern = "/dev/video-dec";
   std::string device_pattern;
   v4l2_buf_type buf_type;
   switch (type) {
     case Type::kDecoder:
       device_pattern = kDecoderDevicePattern;
       buf_type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
       break;
     default:
       LOG(ERROR) << "Only decoder type is supported!!";
       return;
   }

   std::vector<std::string> candidate_paths;

   // TODO(posciak): Remove this legacy unnumbered device once
   // all platforms are updated to use numbered devices.
   candidate_paths.push_back(device_pattern);

   // We are sandboxed, so we can't query directory contents to check which
   // devices are actually available. Try to open the first 10; if not present,
   // we will just fail to open immediately.
   for (int i = 0; i < 10; ++i) {
     candidate_paths.push_back(
         base::StringPrintf("%s%d", device_pattern.c_str(), i));
   }

   Devices devices;
   for (const auto& path : candidate_paths) {
     if (!OpenDevicePath(path, type))
       continue;

     const auto& supported_pixelformats =
         EnumerateSupportedPixelformats(buf_type);
     if (!supported_pixelformats.empty()) {
       DVLOGF(3) << "Found device: " << path;
       devices.push_back(std::make_pair(path, supported_pixelformats));
     }

     CloseDevice();
   }

   DCHECK_EQ(devices_by_type_.count(type), 0u);
   devices_by_type_[type] = devices;
 }

 const V4L2Device::Devices& V4L2Device::GetDevicesForType(Type type) {
   if (devices_by_type_.count(type) == 0)
     EnumerateDevicesForType(type);

   DCHECK_NE(devices_by_type_.count(type), 0u);
   return devices_by_type_[type];
 }

 std::string V4L2Device::GetDevicePathFor(Type type, uint32_t pixfmt) {
   const Devices& devices = GetDevicesForType(type);

   for (const auto& device : devices) {
     if (std::find(device.second.begin(), device.second.end(), pixfmt) !=
         device.second.end())
       return device.first;
   }

   return std::string();
 }

 }  //  namespace media
	// Copyright 2014 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.
	// Note: ported from Chromium commit head: 09ea0d2
	// Note: it's also merged with generic_v4l2_device.cc (head: a9d98e6)

	#include <errno.h>
	#include <fcntl.h>
	#include <poll.h>
	#include <string.h>
	#include <sys/eventfd.h>
	#include <sys/ioctl.h>
	#include <sys/mman.h>

	#include "base/numerics/safe_conversions.h"
	#include "base/posix/eintr_wrapper.h"
	#include "base/strings/stringprintf.h"
	#include "v4l2_device.h"

	#define DVLOGF(level) DVLOG(level) << __func__ << "(): "
	#define VLOGF(level) VLOG(level) << __func__ << "(): "
	#define VPLOGF(level) VPLOG(level) << __func__ << "(): "

	namespace media {

	V4L2Device::V4L2Device() {}

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

	// static
	VideoPixelFormat V4L2Device::V4L2PixFmtToVideoPixelFormat(uint32_t pix_fmt) {
	switch (pix_fmt) {
	case V4L2_PIX_FMT_NV12:
	case V4L2_PIX_FMT_NV12M:
	return PIXEL_FORMAT_NV12;

	case V4L2_PIX_FMT_MT21:
	return PIXEL_FORMAT_MT21;

	case V4L2_PIX_FMT_YUV420:
	case V4L2_PIX_FMT_YUV420M:
	return PIXEL_FORMAT_I420;

	case V4L2_PIX_FMT_YVU420:
	return PIXEL_FORMAT_YV12;

	case V4L2_PIX_FMT_YUV422M:
	return PIXEL_FORMAT_I422;

	case V4L2_PIX_FMT_RGB32:
	return PIXEL_FORMAT_ARGB;

	default:
	DVLOGF(1) << "Add more cases as needed";
	return PIXEL_FORMAT_UNKNOWN;
	}
	}

	// static
	uint32_t V4L2Device::VideoPixelFormatToV4L2PixFmt(VideoPixelFormat format) {
	switch (format) {
	case PIXEL_FORMAT_NV12:
	return V4L2_PIX_FMT_NV12M;

	case PIXEL_FORMAT_MT21:
	return V4L2_PIX_FMT_MT21;

	case PIXEL_FORMAT_I420:
	return V4L2_PIX_FMT_YUV420M;

	case PIXEL_FORMAT_YV12:
	return V4L2_PIX_FMT_YVU420;

	default:
	LOG(FATAL) << "Add more cases as needed";
	return 0;
	}
	}

	// static
	uint32_t V4L2Device::VideoCodecProfileToV4L2PixFmt(VideoCodecProfile profile,
	bool slice_based) {
	if (profile >= H264PROFILE_MIN && profile <= H264PROFILE_MAX) {
	if (slice_based)
	return V4L2_PIX_FMT_H264_SLICE;
	else
	return V4L2_PIX_FMT_H264;
	} else if (profile >= VP8PROFILE_MIN && profile <= VP8PROFILE_MAX) {
	if (slice_based)
	return V4L2_PIX_FMT_VP8_FRAME;
	else
	return V4L2_PIX_FMT_VP8;
	} else if (profile >= VP9PROFILE_MIN && profile <= VP9PROFILE_MAX) {
	if (slice_based)
	return V4L2_PIX_FMT_VP9_FRAME;
	else
	return V4L2_PIX_FMT_VP9;
	} else {
	LOG(FATAL) << "Add more cases as needed";
	return 0;
	}
	}

	// static
	std::vector<VideoCodecProfile> V4L2Device::V4L2PixFmtToVideoCodecProfiles(
	uint32_t pix_fmt,
	bool is_encoder) {
	VideoCodecProfile min_profile, max_profile;
	std::vector<VideoCodecProfile> profiles;

	switch (pix_fmt) {
	case V4L2_PIX_FMT_H264:
	case V4L2_PIX_FMT_H264_SLICE:
	if (is_encoder) {
	// TODO(posciak): need to query the device for supported H.264 profiles,
	// for now choose Main as a sensible default.
	min_profile = H264PROFILE_MAIN;
	max_profile = H264PROFILE_MAIN;
	} else {
	min_profile = H264PROFILE_MIN;
	max_profile = H264PROFILE_MAX;
	}
	break;

	case V4L2_PIX_FMT_VP8:
	case V4L2_PIX_FMT_VP8_FRAME:
	min_profile = VP8PROFILE_MIN;
	max_profile = VP8PROFILE_MAX;
	break;

	case V4L2_PIX_FMT_VP9:
	case V4L2_PIX_FMT_VP9_FRAME:
	min_profile = VP9PROFILE_MIN;
	max_profile = VP9PROFILE_MAX;
	break;

	default:
	VLOGF(1) << "Unhandled pixelformat " << std::hex << "0x" << pix_fmt;
	return profiles;
	}

	for (int profile = min_profile; profile <= max_profile; ++profile)
	profiles.push_back(static_cast<VideoCodecProfile>(profile));

	return profiles;
	}

	int V4L2Device::Ioctl(int request, void* arg) {
	DCHECK(device_fd_.is_valid());
	return HANDLE_EINTR(ioctl(device_fd_.get(), request, arg));
	}

	bool V4L2Device::Poll(bool poll_device, bool* event_pending) {
	struct pollfd pollfds[2];
	nfds_t nfds;
	int pollfd = -1;

	pollfds[0].fd = device_poll_interrupt_fd_.get();
	pollfds[0].events = POLLIN \| POLLERR;
	nfds = 1;

	if (poll_device) {
	DVLOGF(5) << "Poll(): adding device fd to poll() set";
	pollfds[nfds].fd = device_fd_.get();
	pollfds[nfds].events = POLLIN \| POLLOUT \| POLLERR \| POLLPRI;
	pollfd = nfds;
	nfds++;
	}

	if (HANDLE_EINTR(poll(pollfds, nfds, -1)) == -1) {
	VPLOGF(1) << "poll() failed";
	return false;
	}
	*event_pending = (pollfd != -1 && pollfds[pollfd].revents & POLLPRI);
	return true;
	}

	void* V4L2Device::Mmap(void* addr,
	unsigned int len,
	int prot,
	int flags,
	unsigned int offset) {
	DCHECK(device_fd_.is_valid());
	return mmap(addr, len, prot, flags, device_fd_.get(), offset);
	}

	void V4L2Device::Munmap(void* addr, unsigned int len) {
	munmap(addr, len);
	}

	bool V4L2Device::SetDevicePollInterrupt() {
	DVLOGF(4);

	const uint64_t buf = 1;
	if (HANDLE_EINTR(write(device_poll_interrupt_fd_.get(), &buf, sizeof(buf))) ==
	-1) {
	VPLOGF(1) << "write() failed";
	return false;
	}
	return true;
	}

	bool V4L2Device::ClearDevicePollInterrupt() {
	DVLOGF(5);

	uint64_t buf;
	if (HANDLE_EINTR(read(device_poll_interrupt_fd_.get(), &buf, sizeof(buf))) ==
	-1) {
	if (errno == EAGAIN) {
	// No interrupt flag set, and we're reading nonblocking. Not an error.
	return true;
	} else {
	VPLOGF(1) << "read() failed";
	return false;
	}
	}
	return true;
	}

	bool V4L2Device::Open(Type type, uint32_t v4l2_pixfmt) {
	VLOGF(2);
	std::string path = GetDevicePathFor(type, v4l2_pixfmt);

	if (path.empty()) {
	VLOGF(1) << "No devices supporting " << std::hex << "0x" << v4l2_pixfmt
	<< " for type: " << static_cast<int>(type);
	return false;
	}

	if (!OpenDevicePath(path, type)) {
	VLOGF(1) << "Failed opening " << path;
	return false;
	}

	device_poll_interrupt_fd_.reset(eventfd(0, EFD_NONBLOCK \| EFD_CLOEXEC));
	if (!device_poll_interrupt_fd_.is_valid()) {
	VLOGF(1) << "Failed creating a poll interrupt fd";
	return false;
	}

	return true;
	}

	std::vector<base::ScopedFD> V4L2Device::GetDmabufsForV4L2Buffer(
	int index,
	size_t num_planes,
	enum v4l2_buf_type buf_type) {
	VLOGF(2);
	DCHECK(V4L2_TYPE_IS_MULTIPLANAR(buf_type));

	std::vector<base::ScopedFD> dmabuf_fds;
	for (size_t i = 0; i < num_planes; ++i) {
	struct v4l2_exportbuffer expbuf;
	memset(&expbuf, 0, sizeof(expbuf));
	expbuf.type = buf_type;
	expbuf.index = index;
	expbuf.plane = i;
	expbuf.flags = O_CLOEXEC;
	if (Ioctl(VIDIOC_EXPBUF, &expbuf) != 0) {
	dmabuf_fds.clear();
	break;
	}

	dmabuf_fds.push_back(base::ScopedFD(expbuf.fd));
	}

	return dmabuf_fds;
	}

	VideoDecodeAccelerator::SupportedProfiles
	V4L2Device::GetSupportedDecodeProfiles(const size_t num_formats,
	const uint32_t pixelformats[]) {
	VideoDecodeAccelerator::SupportedProfiles supported_profiles;

	Type type = Type::kDecoder;
	const auto& devices = GetDevicesForType(type);
	for (const auto& device : devices) {
	if (!OpenDevicePath(device.first, type)) {
	VLOGF(1) << "Failed opening " << device.first;
	continue;
	}

	const auto& profiles =
	EnumerateSupportedDecodeProfiles(num_formats, pixelformats);
	supported_profiles.insert(supported_profiles.end(), profiles.begin(),
	profiles.end());
	CloseDevice();
	}

	return supported_profiles;
	}

	void V4L2Device::GetSupportedResolution(uint32_t pixelformat,
	Size* min_resolution,
	Size* max_resolution) {
	max_resolution->SetSize(0, 0);
	min_resolution->SetSize(0, 0);
	v4l2_frmsizeenum frame_size;
	memset(&frame_size, 0, sizeof(frame_size));
	frame_size.pixel_format = pixelformat;
	for (; Ioctl(VIDIOC_ENUM_FRAMESIZES, &frame_size) == 0; ++frame_size.index) {
	if (frame_size.type == V4L2_FRMSIZE_TYPE_DISCRETE) {
	if (frame_size.discrete.width >=
	base::checked_cast<uint32_t>(max_resolution->width()) &&
	frame_size.discrete.height >=
	base::checked_cast<uint32_t>(max_resolution->height())) {
	max_resolution->SetSize(frame_size.discrete.width,
	frame_size.discrete.height);
	}
	if (min_resolution->IsEmpty() \|\|
	(frame_size.discrete.width <=
	base::checked_cast<uint32_t>(min_resolution->width()) &&
	frame_size.discrete.height <=
	base::checked_cast<uint32_t>(min_resolution->height()))) {
	min_resolution->SetSize(frame_size.discrete.width,
	frame_size.discrete.height);
	}
	} else if (frame_size.type == V4L2_FRMSIZE_TYPE_STEPWISE \|\|
	frame_size.type == V4L2_FRMSIZE_TYPE_CONTINUOUS) {
	max_resolution->SetSize(frame_size.stepwise.max_width,
	frame_size.stepwise.max_height);
	min_resolution->SetSize(frame_size.stepwise.min_width,
	frame_size.stepwise.min_height);
	break;
	}
	}
	if (max_resolution->IsEmpty()) {
	max_resolution->SetSize(1920, 1088);
	VLOGF(1) << "GetSupportedResolution failed to get maximum resolution for "
	<< "fourcc " << std::hex << pixelformat
	<< ", fall back to " << max_resolution->ToString();
	}
	if (min_resolution->IsEmpty()) {
	min_resolution->SetSize(16, 16);
	VLOGF(1) << "GetSupportedResolution failed to get minimum resolution for "
	<< "fourcc " << std::hex << pixelformat
	<< ", fall back to " << min_resolution->ToString();
	}
	}

	std::vector<uint32_t> V4L2Device::EnumerateSupportedPixelformats(
	v4l2_buf_type buf_type) {
	std::vector<uint32_t> pixelformats;

	v4l2_fmtdesc fmtdesc;
	memset(&fmtdesc, 0, sizeof(fmtdesc));
	fmtdesc.type = buf_type;

	for (; Ioctl(VIDIOC_ENUM_FMT, &fmtdesc) == 0; ++fmtdesc.index) {
	DVLOGF(3) << "Found " << fmtdesc.description << std::hex << " (0x"
	<< fmtdesc.pixelformat << ")";
	pixelformats.push_back(fmtdesc.pixelformat);
	}

	return pixelformats;
	}

	VideoDecodeAccelerator::SupportedProfiles
	V4L2Device::EnumerateSupportedDecodeProfiles(const size_t num_formats,
	const uint32_t pixelformats[]) {
	VideoDecodeAccelerator::SupportedProfiles profiles;

	const auto& supported_pixelformats =
	EnumerateSupportedPixelformats(V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE);

	for (uint32_t pixelformat : supported_pixelformats) {
	if (std::find(pixelformats, pixelformats + num_formats, pixelformat) ==
	pixelformats + num_formats)
	continue;

	VideoDecodeAccelerator::SupportedProfile profile;
	GetSupportedResolution(pixelformat, &profile.min_resolution,
	&profile.max_resolution);

	const auto video_codec_profiles =
	V4L2PixFmtToVideoCodecProfiles(pixelformat, false);

	for (const auto& video_codec_profile : video_codec_profiles) {
	profile.profile = video_codec_profile;
	profiles.push_back(profile);

	DVLOGF(3) << "Found decoder profile " << GetProfileName(profile.profile)
	<< ", resolutions: " << profile.min_resolution.ToString() << " "
	<< profile.max_resolution.ToString();
	}
	}

	return profiles;
	}

	bool V4L2Device::OpenDevicePath(const std::string& path, Type type) {
	DCHECK(!device_fd_.is_valid());

	device_fd_.reset(
	HANDLE_EINTR(open(path.c_str(), O_RDWR \| O_NONBLOCK \| O_CLOEXEC)));
	if (!device_fd_.is_valid())
	return false;

	return true;
	}

	void V4L2Device::CloseDevice() {
	VLOGF(2);
	device_fd_.reset();
	}

	void V4L2Device::EnumerateDevicesForType(Type type) {
	static const std::string kDecoderDevicePattern = "/dev/video-dec";
	std::string device_pattern;
	v4l2_buf_type buf_type;
	switch (type) {
	case Type::kDecoder:
	device_pattern = kDecoderDevicePattern;
	buf_type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
	break;
	default:
	LOG(ERROR) << "Only decoder type is supported!!";
	return;
	}

	std::vector<std::string> candidate_paths;

	// TODO(posciak): Remove this legacy unnumbered device once
	// all platforms are updated to use numbered devices.
	candidate_paths.push_back(device_pattern);

	// We are sandboxed, so we can't query directory contents to check which
	// devices are actually available. Try to open the first 10; if not present,
	// we will just fail to open immediately.
	for (int i = 0; i < 10; ++i) {
	candidate_paths.push_back(
	base::StringPrintf("%s%d", device_pattern.c_str(), i));
	}

	Devices devices;
	for (const auto& path : candidate_paths) {
	if (!OpenDevicePath(path, type))
	continue;

	const auto& supported_pixelformats =
	EnumerateSupportedPixelformats(buf_type);
	if (!supported_pixelformats.empty()) {
	DVLOGF(3) << "Found device: " << path;
	devices.push_back(std::make_pair(path, supported_pixelformats));
	}

	CloseDevice();
	}

	DCHECK_EQ(devices_by_type_.count(type), 0u);
	devices_by_type_[type] = devices;
	}

	const V4L2Device::Devices& V4L2Device::GetDevicesForType(Type type) {
	if (devices_by_type_.count(type) == 0)
	EnumerateDevicesForType(type);

	DCHECK_NE(devices_by_type_.count(type), 0u);
	return devices_by_type_[type];
	}

	std::string V4L2Device::GetDevicePathFor(Type type, uint32_t pixfmt) {
	const Devices& devices = GetDevicesForType(type);

	for (const auto& device : devices) {
	if (std::find(device.second.begin(), device.second.end(), pixfmt) !=
	device.second.end())
	return device.first;
	}

	return std::string();
	}

	} // namespace media