diff options
author | Hans Verkuil <hans.verkuil@cisco.com> | 2012-09-07 04:46:39 -0300 |
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committer | Mauro Carvalho Chehab <mchehab@redhat.com> | 2013-01-05 00:49:54 -0200 |
commit | 8ac7a9493a4380a8a886fbfe311ab00bc424ca0f (patch) | |
tree | 25f60268aad8cf9f45c44b1ef7e8a2f30e506952 /Documentation/video4linux/v4l2-controls.txt | |
parent | 20deebfe17b20ded00ba404adbcd014eb2b024c1 (diff) | |
download | linux-8ac7a9493a4380a8a886fbfe311ab00bc424ca0f.tar.bz2 |
[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 <hans.verkuil@cisco.com>
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'Documentation/video4linux/v4l2-controls.txt')
-rw-r--r-- | Documentation/video4linux/v4l2-controls.txt | 22 |
1 files changed, 14 insertions, 8 deletions
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. |