Linux Video Capture: Add V4L2VideoCaptureDelegate{Single,Multi}Plane.

media/video/capture/linux/v4l2_capture_delegate_multi_plane.cc

+// Copyright 2015 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.
+
+#include "media/video/capture/linux/v4l2_capture_delegate_multi_plane.h"
+
+#include <sys/mman.h>
+
+namespace media {
+
+V4L2CaptureDelegateMultiPlane::V4L2CaptureDelegateMultiPlane(
+    const VideoCaptureDevice::Name& device_name,
+    const scoped_refptr<base::SingleThreadTaskRunner>& v4l2_task_runner,
+    int power_line_frequency)
+    : V4L2VideoCaptureDelegate(device_name,
+                               v4l2_task_runner,
+                               power_line_frequency) {
+}
+
+V4L2CaptureDelegateMultiPlane::~V4L2CaptureDelegateMultiPlane() {
+}
+
+scoped_refptr<V4L2VideoCaptureDelegate::BufferTracker>
+V4L2CaptureDelegateMultiPlane::CreateBufferTracker() {
+  return make_scoped_refptr(new BufferTrackerMPlane());
+}
+
+bool V4L2CaptureDelegateMultiPlane::FillV4L2Format(
+    v4l2_format* format,
+    uint32_t width,
+    uint32_t height,
+    uint32_t pixelformat_fourcc) {
+  format->fmt.pix_mp.width = width;
+  format->fmt.pix_mp.height = height;
+  format->fmt.pix_mp.pixelformat = pixelformat_fourcc;
+
+  const size_t num_v4l2_planes =
+      V4L2VideoCaptureDelegate::GetNumPlanesForFourCc(pixelformat_fourcc);
+  if (num_v4l2_planes == 0u)
+    return false;
+  DCHECK_LE(num_v4l2_planes, static_cast<size_t>(VIDEO_MAX_PLANES));
+  format->fmt.pix_mp.num_planes = num_v4l2_planes;
+
+  v4l2_planes_.resize(num_v4l2_planes);
+  return true;
+}
+
+void V4L2CaptureDelegateMultiPlane::FinishFillingV4L2Buffer(
+    v4l2_buffer* buffer) const {
+  buffer->type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
+  buffer->length = v4l2_planes_.size();
+  buffer->m.planes = const_cast<struct v4l2_plane*>(v4l2_planes_.data());

[Pawel Osciak, 2015/03/19 07:52:43]

memset to 0 please
Also, why do we need this cast? There is a non-const version of data(), and we
*will* be changing the memory, so const is not good.

[mcasas, 2015/03/19 22:57:00]

Done.
The compiler saw that the method is marked |const|
and used:
const T* data() const;

const_cast is a way around, since it eliminates the 
constness.

Alternatively, I marked |v4l2_planes_| as mutable, 
since is a scratchpad and can be used in const
methods without further ado.

As a side bonus, this mutable allows for
FillV4L2Format() to be marked const as well.

[Pawel Osciak, 2015/03/20 00:56:06]

The method should not be const?

+}
+
+void V4L2CaptureDelegateMultiPlane::SendBuffer(
+    const scoped_refptr<BufferTracker>& buffer_tracker) {
+  DCHECK_EQ(capture_format().pixel_format, PIXEL_FORMAT_I420);
+  client()->OnIncomingCapturedYuvData(buffer_tracker->GetPlaneStart(0),
+                                      buffer_tracker->GetPlaneStart(1),

[Pawel Osciak, 2015/03/19 07:52:43]

This makes me nervous. I'd like to have a check in GetPlaneStart/Length() that
we have enough size().

[mcasas, 2015/03/19 22:57:00]

Done. DCHECK is good for me, but please speak up
otherwise.

[Pawel Osciak, 2015/03/20 00:56:06]

I'd prefer something stronger please, better than invalid memory access issues.

+                                      buffer_tracker->GetPlaneStart(2),
+                                      buffer_tracker->GetPlaneLength(0),

[perkj_chrome, 2015/03/19 20:38:17]

I think this should be the stride instead of the plane length. 

[mcasas, 2015/03/19 22:57:00]

Done.

+                                      buffer_tracker->GetPlaneLength(1),
+                                      buffer_tracker->GetPlaneLength(2),
+                                      capture_format(),
+                                      rotation(),
+                                      base::TimeTicks::Now());
+}
+
+bool V4L2CaptureDelegateMultiPlane::BufferTrackerMPlane::Init(
+    int fd,
+    const v4l2_buffer& buffer) {
+  for (size_t p = 0; p < buffer.length; ++p) {
+    void* const start =
+        mmap(NULL, buffer.m.planes[p].length, PROT_READ | PROT_WRITE,

[Pawel Osciak, 2015/03/19 07:52:43]

// Some devices require mmap() to be called with both READ and WRITE.
// See http://crbug.com/178582.

[mcasas, 2015/03/19 22:57:00]

Done.

+             MAP_SHARED, fd, buffer.m.planes[p].m.mem_offset);
+    if (start == MAP_FAILED) {
+      DLOG(ERROR) << "Error mmap()ing a V4L2 buffer into userspace";
+      return false;
+    }
+    AddMmapedPlane(start, buffer.m.planes[p].length);
+    DVLOG(3) << "Mmap()ed plane #" << p << " of " << GetPlaneLength(p) << "B";
+  }
+  return true;
+}
+
+}  // namespace media