Image Capture v4l2: reset all user controls to default values when closing device fd

media/capture/video/linux/v4l2_capture_delegate.cc

Index: media/capture/video/linux/v4l2_capture_delegate.cc
diff --git a/media/capture/video/linux/v4l2_capture_delegate.cc b/media/capture/video/linux/v4l2_capture_delegate.cc
index 8b48b8a1f087cf44a44001c78d1b8a4969a17e9c..8587b37479dc25cc6a0e3a565ca1b895e29a57ea 100644
--- a/media/capture/video/linux/v4l2_capture_delegate.cc
+++ b/media/capture/video/linux/v4l2_capture_delegate.cc
@@ -5,6 +5,7 @@
 #include "media/capture/video/linux/v4l2_capture_delegate.h"
 
 #include <linux/version.h>
+#include <linux/videodev2.h>
 #include <poll.h>
 #include <sys/fcntl.h>
 #include <sys/ioctl.h>
@@ -52,6 +53,8 @@ const int kMjpegHeight = 480;
 // Typical framerate, in fps
 const int kTypicalFramerate = 30;
 
+const int kMaxIOCtrlRetries = 5;

[emircan, 2016/12/07 21:45:31]

Add a comment for this here as well.

[mcasas, 2016/12/08 23:46:52]

Done.

+
 // V4L2 color formats supported by V4L2CaptureDelegate derived classes.
 // This list is ordered by precedence of use -- but see caveats for MJPEG.
 static struct {
@@ -134,6 +137,115 @@ static mojom::RangePtr RetrieveUserControlRange(int device_fd, int control_id) {
   return capability;
 }
 
+// Determines if a |control_id| is special, i.e. controls another one's state.
+static bool IsSpecialControl(int control_id) {
+  if (control_id == V4L2_CID_AUTO_WHITE_BALANCE)

[emircan, 2016/12/07 21:45:31]

Can you regroup this into a switch statement?

[mcasas, 2016/12/08 23:46:52]

Done.

+    return true;
+  else if (control_id == V4L2_CID_EXPOSURE_AUTO)
+    return true;
+  else if (control_id == V4L2_CID_EXPOSURE_AUTO_PRIORITY)
+    return true;
+  else if (control_id == V4L2_CID_FOCUS_AUTO)
+    return true;
+  return false;
+}
+
+// Sets all user control to their default. Some controls are enabled by another
+// flag, usually having the word "auto" in the name, see ISpecialControl().
+// These flags are preset beforehand.
+static void ResetUserAndCameraControlsToDefault(int device_fd) {
+  // Set V4L2_CID_AUTO_WHITE_BALANCE to false first.
+  v4l2_control auto_white_balance = {};
+  auto_white_balance.id = V4L2_CID_AUTO_WHITE_BALANCE;
+  auto_white_balance.value = false;
+  int num_retries = 0;
+  // Setting up the first control right after stopping streaming seems
+  // not to the work the first time, so retry a few times.
+  for (; num_retries < kMaxIOCtrlRetries &&
+         HANDLE_EINTR(ioctl(device_fd, VIDIOC_S_CTRL, &auto_white_balance)) < 0;

[emircan, 2016/12/07 21:45:31]

Would it help to log the return value here? 

[mcasas, 2016/12/08 23:46:52]

Not really, DPLOG() in l.167 will show what has
happened better than us.

+       ++num_retries) {
+    DPLOG(WARNING) << "VIDIOC_S_CTRL";
+  }
+  if (num_retries == kMaxIOCtrlRetries) {
+    DLOG(ERROR) << "Cannot access device controls";
+    return;
+  }
+
+  std::vector<struct v4l2_ext_control> user_controls;
+  for (int control_id = V4L2_CID_USER_BASE; control_id < V4L2_CID_LASTP1;
+       ++control_id) {
+    if (IsSpecialControl(control_id))

[emircan, 2016/12/07 21:45:31]

Can you refactor l.177-187 and l.226-236 into a static method? You can even use
it in the unittest.

[mcasas, 2016/12/08 23:46:52]

I've rewritten the whole implementation so it's
hopefully simpler, and it's based on the --according
to the online doc-- standard way of iterating over
the controls using a while and some flag-bit logic.

+      continue;
+    v4l2_queryctrl range = {};
+    range.id = control_id;
+    if (HANDLE_EINTR(ioctl(device_fd, VIDIOC_QUERYCTRL, &range)) < 0)
+      continue;
+
+    struct v4l2_ext_control ext_control = {};
+    ext_control.id = control_id;
+    ext_control.value = range.default_value;
+    user_controls.push_back(ext_control);
+  }
+
+  if (!user_controls.empty()) {
+    struct v4l2_ext_controls ext_controls = {};
+    ext_controls.ctrl_class = V4L2_CTRL_CLASS_USER;
+    ext_controls.count = user_controls.size();
+    ext_controls.controls = user_controls.data();
+    if (HANDLE_EINTR(ioctl(device_fd, VIDIOC_S_EXT_CTRLS, &ext_controls)) < 0)
+      DPLOG(ERROR) << "VIDIOC_S_EXT_CTRLS";
+  }
+
+  std::vector<struct v4l2_ext_control> special_camera_controls;
+  // Set V4L2_CID_EXPOSURE_AUTO to V4L2_EXPOSURE_MANUAL.
+  v4l2_ext_control auto_exposure = {};
+  auto_exposure.id = V4L2_CID_EXPOSURE_AUTO;
+  auto_exposure.value = V4L2_EXPOSURE_MANUAL;
+  special_camera_controls.push_back(auto_exposure);
+  // Set V4L2_CID_EXPOSURE_AUTO_PRIORITY to false.
+  v4l2_ext_control priority_auto_exposure = {};
+  priority_auto_exposure.id = V4L2_CID_EXPOSURE_AUTO_PRIORITY;
+  priority_auto_exposure.value = false;
+  special_camera_controls.push_back(priority_auto_exposure);
+  // Set V4L2_CID_FOCUS_AUTO to false.
+  v4l2_ext_control auto_focus = {};
+  auto_focus.id = V4L2_CID_FOCUS_AUTO;
+  auto_focus.value = false;
+  special_camera_controls.push_back(auto_focus);
+
+  struct v4l2_ext_controls ext_controls = {};
+  ext_controls.ctrl_class = V4L2_CID_CAMERA_CLASS;
+  ext_controls.count = special_camera_controls.size();
+  ext_controls.controls = special_camera_controls.data();
+  if (HANDLE_EINTR(ioctl(device_fd, VIDIOC_S_EXT_CTRLS, &ext_controls)) < 0)
+    DPLOG(ERROR) << "VIDIOC_S_EXT_CTRLS";
+
+  std::vector<struct v4l2_ext_control> camera_controls;
+  for (int control_id = V4L2_CID_CAMERA_CLASS_BASE;
+       control_id < V4L2_CID_CAMERA_CLASS_BASE + 32; ++control_id) {

[emircan, 2016/12/07 21:45:31]

Where is this 32 coming from? I was doing a quick search on this and it looks
like it can extend to 33:
http://lxr.free-electrons.com/source/include/uapi/linux/v4l2-controls.h#L760

[mcasas, 2016/12/08 23:46:52]

In the latest kernel yes, but in the 3.13 that
we use for compiling, there's just 32 [1].
However, thanks for pointing this out, the
way to work with the Camera Controls is to 
iterate over them, not to try a fixed number,
so, changed.

[1]
http://lxr.free-electrons.com/source/include/uapi/linux/v4l2-controls.h?v=3.13

+    if (IsSpecialControl(control_id))
+      continue;
+    v4l2_queryctrl range = {};
+    range.id = control_id;
+    if (HANDLE_EINTR(ioctl(device_fd, VIDIOC_QUERYCTRL, &range)) < 0)
+      continue;
+
+    struct v4l2_ext_control ext_control = {};
+    ext_control.id = control_id;
+    ext_control.value = range.default_value;
+    camera_controls.push_back(ext_control);
+  }
+
+  if (!camera_controls.empty()) {
+    struct v4l2_ext_controls ext_controls = {};
+    ext_controls.ctrl_class = V4L2_CID_CAMERA_CLASS;
+    ext_controls.count = camera_controls.size();
+    ext_controls.controls = camera_controls.data();
+    if (HANDLE_EINTR(ioctl(device_fd, VIDIOC_S_EXT_CTRLS, &ext_controls)) < 0)
+      DPLOG(ERROR) << "VIDIOC_S_EXT_CTRLS";
+  }
+}
+
 // Class keeping track of a SPLANE V4L2 buffer, mmap()ed on construction and
 // munmap()ed on destruction.
 class V4L2CaptureDelegate::BufferTracker
@@ -355,6 +467,7 @@ void V4L2CaptureDelegate::StopAndDeAllocate() {
   if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_REQBUFS, &r_buffer)) < 0)
     SetErrorState(FROM_HERE, "Failed to VIDIOC_REQBUFS with count = 0");
 
+  ResetUserAndCameraControlsToDefault(device_fd_.get());
   // At this point we can close the device.
   // This is also needed for correctly changing settings later via VIDIOC_S_FMT.
   device_fd_.reset();