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[media] media/Documentation: New flag EXECUTE_ON_WRITE

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Document new flag V4L2_CTRL_FLAG_EXECUTE_ON_WRITE, and the new behavior
of CH_VALUE event on VOLATILE controls.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
This commit is contained in:
Ricardo Ribalda 2015-03-20 11:13:14 -03:00 committed by Mauro Carvalho Chehab
parent 45f014c526
commit acd2b672b4
3 changed files with 17 additions and 5 deletions
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6
Documentation/DocBook/media/v4l/vidioc-dqevent.xml
View File

@ -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>

12
Documentation/DocBook/media/v4l/vidioc-queryctrl.xml
View File

@ -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>

4
Documentation/video4linux/v4l2-controls.txt
View File

@ -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: