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-rw-r--r--Documentation/DocBook/media/v4l/vidioc-queryctrl.xml12
1 files changed, 11 insertions, 1 deletions
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>