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Commit acd2b672 authored by Ricardo Ribalda Delgado's avatar Ricardo Ribalda Delgado Committed by Mauro Carvalho Chehab
Browse files

[media] media/Documentation: New flag EXECUTE_ON_WRITE 



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

Signed-off-by: default avatarRicardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@osg.samsung.com>
parent 45f014c5

Documentation/DocBook/media/v4l/vidioc-dqevent.xml

+3 −3
Original line number Original line Diff line number Diff line
@@ -425,9 +425,9 @@ 
	    <entry><constant>V4L2_EVENT_CTRL_CH_VALUE</constant></entry>

	    <entry><constant>V4L2_EVENT_CTRL_CH_VALUE</constant></entry>

	    <entry>0x0001</entry>

	    <entry>0x0001</entry>

	    <entry>This control event was triggered because the value of the control

	    <entry>This control event was triggered because the value of the control

		changed. Special case: if a button control is pressed, then this

		changed. Special cases: Volatile controls do no generate this event;

		event is sent as well, even though there is not explicit value

		If a control has the <constant>V4L2_CTRL_FLAG_EXECUTE_ON_WRITE</constant>

		associated with a button control.</entry>

		flag set, then this event is sent as well, regardless its value.</entry>

	  </row>

	  </row>

	  <row>

	  <row>

	    <entry><constant>V4L2_EVENT_CTRL_CH_FLAGS</constant></entry>

	    <entry><constant>V4L2_EVENT_CTRL_CH_FLAGS</constant></entry>

Documentation/DocBook/media/v4l/vidioc-queryctrl.xml

+11 −1
Original line number Original line Diff line number Diff line
@@ -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

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

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

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>

	  <row>

	  <row>

	    <entry><constant>V4L2_CTRL_FLAG_HAS_PAYLOAD</constant></entry>

	    <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

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>

pointer to memory containing the payload of the control.</entry>

	  </row>

	  </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>

	</tbody>

      </tgroup>

      </tgroup>

    </table>

    </table>

Documentation/video4linux/v4l2-controls.txt

+3 −1
Original line number Original line Diff line number Diff line
@@ -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

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:

To mark a control as volatile you have to set V4L2_CTRL_FLAG_VOLATILE: