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Diffstat (limited to 'Documentation/video4linux/v4l2-controls.txt')
| -rw-r--r-- | Documentation/video4linux/v4l2-controls.txt | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/video4linux/v4l2-controls.txt b/Documentation/video4linux/v4l2-controls.txt index 8773778d23fc..881e7f44491b 100644 --- a/Documentation/video4linux/v4l2-controls.txt +++ b/Documentation/video4linux/v4l2-controls.txt @@ -285,6 +285,9 @@ implement g_volatile_ctrl like this: The 'new value' union is not used in g_volatile_ctrl. In general controls that need to implement g_volatile_ctrl are read-only controls. +Note that if one or more controls in a control cluster are marked as volatile, +then all the controls in the cluster are seen as volatile. + To mark a control as volatile you have to set the is_volatile flag: ctrl = v4l2_ctrl_new_std(&sd->ctrl_handler, ...); @@ -462,6 +465,15 @@ pointer to the v4l2_ctrl_ops struct that is used for that cluster. Obviously, all controls in the cluster array must be initialized to either a valid control or to NULL. +In rare cases you might want to know which controls of a cluster actually +were set explicitly by the user. For this you can check the 'is_new' flag of +each control. For example, in the case of a volume/mute cluster the 'is_new' +flag of the mute control would be set if the user called VIDIOC_S_CTRL for +mute only. If the user would call VIDIOC_S_EXT_CTRLS for both mute and volume +controls, then the 'is_new' flag would be 1 for both controls. + +The 'is_new' flag is always 1 when called from v4l2_ctrl_handler_setup(). + VIDIOC_LOG_STATUS Support ========================= |