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[media] Docbook: media: Document changes on struct v4l2_ext_controls

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Vidioc-g-ext-ctrls can now be used to get the default value of the
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 2015-10-29 08:10:32 -02:00 committed by Mauro Carvalho Chehab
parent 082afb7c4e
commit 5d273c7513
2 changed files with 32 additions and 0 deletions
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10
Documentation/DocBook/media/v4l/v4l2.xml
View File

@ -151,6 +151,16 @@ Rubli, Andy Walls, Muralidharan Karicheri, Mauro Carvalho Chehab,
structs, ioctls) must be noted in more detail in the history chapter
(compat.xml), along with the possible impact on existing drivers and
applications. -->
<revision>
<revnumber>4.5</revnumber>
<date>2015-10-29</date>
<authorinitials>rr</authorinitials>
<revremark>Extend vidioc-g-ext-ctrls;. Replace ctrl_class with a new
union with ctrl_class and which. Which is used to select the current value of
the control or the default value.
</revremark>
</revision>
<revision>
<revnumber>4.4</revnumber>
<date>2015-05-26</date>

22
Documentation/DocBook/media/v4l/vidioc-g-ext-ctrls.xml
View File

@ -223,7 +223,12 @@ Valid if <constant>V4L2_CTRL_FLAG_HAS_PAYLOAD</constant> is set for this control
<tgroup cols="3">
&cs-str;
<tbody valign="top">
<row>
<entry>union</entry>
<entry>(anonymous)</entry>
</row>
<row>
<entry></entry>
<entry>__u32</entry>
<entry><structfield>ctrl_class</structfield></entry>
<entry>The control class to which all controls belong, see
@ -233,6 +238,23 @@ belong to any control class. Whether drivers support this can be tested by setti
<structfield>ctrl_class</structfield> to 0 and calling <constant>VIDIOC_TRY_EXT_CTRLS</constant>
with a <structfield>count</structfield> of 0. If that succeeds, then the driver
supports this feature.</entry>
</row>
<row>
<entry></entry>
<entry>__u32</entry>
<entry><structfield>which</structfield></entry>
<entry><para>Which value of the control to get/set/try. <constant>V4L2_CTRL_WHICH_CUR_VAL</constant>
will return the current value of the control and <constant>V4L2_CTRL_WHICH_DEF_VAL</constant> will
return the default value of the control. Please note that you can only get the default value of the
control, you cannot set or try it.</para>
<para>For backwards compatibility you can also use a control class here (see
<xref linkend="ctrl-class" />). In that case all controls have to belong to that
control class. This usage is deprecated, instead just use <constant>V4L2_CTRL_WHICH_CUR_VAL</constant>.
There are some very old drivers that do not yet support <constant>V4L2_CTRL_WHICH_CUR_VAL</constant>
and that require a control class here. You can test for such drivers by setting ctrl_class to
<constant>V4L2_CTRL_WHICH_CUR_VAL</constant> and calling VIDIOC_TRY_EXT_CTRLS with a count of 0.
If that fails, then the driver does not support <constant>V4L2_CTRL_WHICH_CUR_VAL</constant>.</para>
</entry>
</row>
<row>
<entry>__u32</entry>