From 8ac7a9493a4380a8a886fbfe311ab00bc424ca0f Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Fri, 7 Sep 2012 04:46:39 -0300 Subject: [media] v4l2-ctrls: add a notify callback Sometimes platform/bridge drivers need to be notified when a control from a sub-device changes value. In order to support this a notify callback was added. [dheitmueller@kernellabs.com: fix merge conflict in v4l2-ctrls.c] Signed-off-by: Hans Verkuil Signed-off-by: Devin Heitmueller Signed-off-by: Mauro Carvalho Chehab --- Documentation/video4linux/v4l2-controls.txt | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) (limited to 'Documentation/video4linux') diff --git a/Documentation/video4linux/v4l2-controls.txt b/Documentation/video4linux/v4l2-controls.txt index cfe52c798d74..676f87366025 100644 --- a/Documentation/video4linux/v4l2-controls.txt +++ b/Documentation/video4linux/v4l2-controls.txt @@ -715,14 +715,20 @@ a control of this type whenever the first control belonging to a new control class is added. -Proposals for Extensions -======================== +Adding Notify Callbacks +======================= + +Sometimes the platform or bridge driver needs to be notified when a control +from a sub-device driver changes. You can set a notify callback by calling +this function: -Some ideas for future extensions to the spec: +void v4l2_ctrl_notify(struct v4l2_ctrl *ctrl, + void (*notify)(struct v4l2_ctrl *ctrl, void *priv), void *priv); -1) Add a V4L2_CTRL_FLAG_HEX to have values shown as hexadecimal instead of -decimal. Useful for e.g. video_mute_yuv. +Whenever the give control changes value the notify callback will be called +with a pointer to the control and the priv pointer that was passed with +v4l2_ctrl_notify. Note that the control's handler lock is held when the +notify function is called. -2) It is possible to mark in the controls array which controls have been -successfully written and which failed by for example adding a bit to the -control ID. Not sure if it is worth the effort, though. +There can be only one notify function per control handler. Any attempt +to set another notify function will cause a WARN_ON. -- cgit v1.2.2