diff options
| -rw-r--r-- | Documentation/DocBook/media/v4l/vidioc-dqevent.xml | 6 | ||||
| -rw-r--r-- | Documentation/DocBook/media/v4l/vidioc-queryctrl.xml | 12 | ||||
| -rw-r--r-- | Documentation/video4linux/v4l2-controls.txt | 4 |
3 files changed, 17 insertions, 5 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-dqevent.xml b/Documentation/DocBook/media/v4l/vidioc-dqevent.xml index a31eea07d455..50ccd33948c1 100644 --- a/Documentation/DocBook/media/v4l/vidioc-dqevent.xml +++ b/Documentation/DocBook/media/v4l/vidioc-dqevent.xml @@ -425,9 +425,9 @@ <entry><constant>V4L2_EVENT_CTRL_CH_VALUE</constant></entry> <entry>0x0001</entry> <entry>This control event was triggered because the value of the control - changed. Special case: if a button control is pressed, then this - event is sent as well, even though there is not explicit value - associated with a button control.</entry> + changed. Special cases: Volatile controls do no generate this event; + If a control has the <constant>V4L2_CTRL_FLAG_EXECUTE_ON_WRITE</constant> + flag set, then this event is sent as well, regardless its value.</entry> </row> <row> <entry><constant>V4L2_EVENT_CTRL_CH_FLAGS</constant></entry> diff --git a/Documentation/DocBook/media/v4l/vidioc-queryctrl.xml b/Documentation/DocBook/media/v4l/vidioc-queryctrl.xml index 2bd98fd7a4e5..dc83ad70f8dc 100644 --- a/Documentation/DocBook/media/v4l/vidioc-queryctrl.xml +++ b/Documentation/DocBook/media/v4l/vidioc-queryctrl.xml @@ -600,7 +600,9 @@ writing a value will cause the device to carry out a given action changes continuously. A typical example would be the current gain value if the device is in auto-gain mode. In such a case the hardware calculates the gain value based on the lighting conditions which can change over time. Note that setting a new value for -a volatile control will have no effect. The new value will just be ignored.</entry> +a volatile control will have no effect and no <constant>V4L2_EVENT_CTRL_CH_VALUE</constant> +will be sent, unless the <constant>V4L2_CTRL_FLAG_EXECUTE_ON_WRITE</constant> flag +(see below) is also set. Otherwise the new value will just be ignored.</entry> </row> <row> <entry><constant>V4L2_CTRL_FLAG_HAS_PAYLOAD</constant></entry> @@ -610,6 +612,14 @@ using one of the pointer fields of &v4l2-ext-control;. This flag is set for cont that are an array, string, or have a compound type. In all cases you have to set a pointer to memory containing the payload of the control.</entry> </row> + <row> + <entry><constant>V4L2_CTRL_FLAG_EXECUTE_ON_WRITE</constant></entry> + <entry>0x0200</entry> + <entry>The value provided to the control will be propagated to the driver +even if remains constant. This is required when the control represents an action +on the hardware. For example: clearing an error flag or triggering the flash. All the +controls of the type <constant>V4L2_CTRL_TYPE_BUTTON</constant> have this flag set.</entry> + </row> </tbody> </tgroup> </table> diff --git a/Documentation/video4linux/v4l2-controls.txt b/Documentation/video4linux/v4l2-controls.txt index 0f84ce8c9a7b..5517db602f37 100644 --- a/Documentation/video4linux/v4l2-controls.txt +++ b/Documentation/video4linux/v4l2-controls.txt @@ -344,7 +344,9 @@ implement g_volatile_ctrl like this: } Note that you use the 'new value' union as well in g_volatile_ctrl. In general -controls that need to implement g_volatile_ctrl are read-only controls. +controls that need to implement g_volatile_ctrl are read-only controls. If they +are not, a V4L2_EVENT_CTRL_CH_VALUE will not be generated when the control +changes. To mark a control as volatile you have to set V4L2_CTRL_FLAG_VOLATILE: |