[media] v4l2: use new flag to enable core priority handling

Rather than guess which driver supports core priority handling, require drivers
that do to explicitly set the V4L2_FL_USE_FH_PRIO flag in video_device.

Updated the core prio handling accordingly and set the flag in the three
drivers that do.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt
index 7d09114af00..3b15608ee07 100644
--- a/Documentation/video4linux/v4l2-framework.txt
+++ b/Documentation/video4linux/v4l2-framework.txt
@@ -577,6 +577,10 @@ You should also set these fields:
   (cx8802). Since the v4l2_device cannot be associated with a particular
   PCI device it is setup without a parent device. But when the struct
   video_device is setup you do know which parent PCI device to use.
+- flags: optional. Set to V4L2_FL_USE_FH_PRIO if you want to let the framework
+  handle the VIDIOC_G/S_PRIORITY ioctls. This requires that you use struct
+  v4l2_fh. Eventually this flag will disappear once all drivers use the core
+  priority handling. But for now it has to be set explicitly.
 
 If you use v4l2_ioctl_ops, then you should set .unlocked_ioctl to video_ioctl2
 in your v4l2_file_operations struct.
@@ -775,7 +779,8 @@ struct v4l2_fh
 
 struct v4l2_fh provides a way to easily keep file handle specific data
 that is used by the V4L2 framework. New drivers must use struct v4l2_fh
-since it is also used to implement priority handling (VIDIOC_G/S_PRIORITY).
+since it is also used to implement priority handling (VIDIOC_G/S_PRIORITY)
+if the video_device flag V4L2_FL_USE_FH_PRIO is also set.
 
 The users of v4l2_fh (in the V4L2 framework, not the driver) know
 whether a driver uses v4l2_fh as its file->private_data pointer by