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..e38ad1d286ac3909c438fd3086d0d91cc7b01a85 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(V4L2Device::Type::kJpegDecoder, 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;
@@ -253,16 +258,13 @@ void V4L2JpegDecodeAccelerator::Decode(
                             base::Unretained(this), base::Passed(&job_record)));
 }
 
+// static
 bool V4L2JpegDecodeAccelerator::IsSupported() {
-  v4l2_fmtdesc fmtdesc;
-  memset(&fmtdesc, 0, sizeof(fmtdesc));
-  fmtdesc.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+  scoped_refptr<V4L2Device> device = V4L2Device::Create();
+  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_);

[kcwu, 2016/10/07 11:19:05]

I found this check is contradiction to line 459.

[Pawel Osciak, 2016/10/11 06:13:46]

My guess is that the intention here could have been that normally streamoff
should have been called, but this method is intended to clean up no matter what,
so in debug builds it will check to give a chance to fix the code, in Release
just try to do this anyway just in case.
But if there is an issue, we should rather try to fix it, than do this, but out
of scope of this CL though I'd say.

 
+  free_input_buffers_.clear();
+
+  if (input_buffer_map_.empty())
+    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_);

[kcwu, 2016/10/07 11:19:05]

I found this check is contradiction to line 489.

[Pawel Osciak, 2016/10/11 06:13:46]

Please see above.

 
+  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() {