Add support for multiple V4L2 video devices of the same type.

media/gpu/v4l2_jpeg_decode_accelerator.cc

Index: media/gpu/v4l2_jpeg_decode_accelerator.cc
diff --git a/media/gpu/v4l2_jpeg_decode_accelerator.cc b/media/gpu/v4l2_jpeg_decode_accelerator.cc
index b3109191e150e665911354e8fd7965368a789eb9..f47617408aa6e1da381261c3e3454d9d045cdbe9 100644
--- a/media/gpu/v4l2_jpeg_decode_accelerator.cc
+++ b/media/gpu/v4l2_jpeg_decode_accelerator.cc
@@ -187,6 +187,11 @@ void V4L2JpegDecodeAccelerator::PostNotifyError(int32_t bitstream_buffer_id,
 bool V4L2JpegDecodeAccelerator::Initialize(Client* client) {
   DCHECK(child_task_runner_->BelongsToCurrentThread());
 
+  if (!device_->Open(V4L2_PIX_FMT_JPEG)) {
+    LOG(ERROR) << "Failed to open device";
+    return false;
+  }
+
   // Capabilities check.
   struct v4l2_capability caps;
   const __u32 kCapsRequired = V4L2_CAP_STREAMING | V4L2_CAP_VIDEO_M2M;
@@ -254,15 +259,12 @@ void V4L2JpegDecodeAccelerator::Decode(
 }
 
 bool V4L2JpegDecodeAccelerator::IsSupported() {
-  v4l2_fmtdesc fmtdesc;
-  memset(&fmtdesc, 0, sizeof(fmtdesc));
-  fmtdesc.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+  scoped_refptr<V4L2Device> device =
+      V4L2Device::Create(V4L2Device::Type::kJpegDecoder);
+  if (!device)
+    return false;
 
-  for (; device_->Ioctl(VIDIOC_ENUM_FMT, &fmtdesc) == 0; ++fmtdesc.index) {
-    if (fmtdesc.pixelformat == V4L2_PIX_FMT_JPEG)
-      return true;
-  }
-  return false;
+  return device->IsJpegDecodingSupported();
 }
 
 void V4L2JpegDecodeAccelerator::DecodeTask(
@@ -449,6 +451,11 @@ void V4L2JpegDecodeAccelerator::DestroyInputBuffers() {
   DCHECK(decoder_task_runner_->BelongsToCurrentThread());
   DCHECK(!input_streamon_);
 
+  free_input_buffers_.clear();
+
+  if (input_buffer_map_.empty())

[kcwu, 2016/10/06 10:40:00]

Is this only for optimization? If so, how about separate CL?

[Pawel Osciak, 2016/10/07 08:30:24]

It's possible for this class to be created without actually opening the device.
In that case we may call an ioctl on an invalid fd, since this is called from
the destructor unconditionally.

If there are no buffers allocated, we don't need to call anything, so I feel
it's a good way to prevent that.

+    return;
+
   if (input_streamon_) {
     __u32 type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
     IOCTL_OR_ERROR_RETURN(VIDIOC_STREAMOFF, &type);
@@ -468,13 +475,17 @@ void V4L2JpegDecodeAccelerator::DestroyInputBuffers() {
   IOCTL_OR_LOG_ERROR(VIDIOC_REQBUFS, &reqbufs);
 
   input_buffer_map_.clear();
-  free_input_buffers_.clear();
 }
 
 void V4L2JpegDecodeAccelerator::DestroyOutputBuffers() {
   DCHECK(decoder_task_runner_->BelongsToCurrentThread());
   DCHECK(!output_streamon_);
 
+  free_output_buffers_.clear();
+
+  if (output_buffer_map_.empty())
+    return;
+
   if (output_streamon_) {
     __u32 type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
     IOCTL_OR_ERROR_RETURN(VIDIOC_STREAMOFF, &type);
@@ -494,7 +505,6 @@ void V4L2JpegDecodeAccelerator::DestroyOutputBuffers() {
   IOCTL_OR_LOG_ERROR(VIDIOC_REQBUFS, &reqbufs);
 
   output_buffer_map_.clear();
-  free_output_buffers_.clear();
 }
 
 void V4L2JpegDecodeAccelerator::DevicePollTask() {