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V4L/DVB: V4L Doc: correct the documentation for VIDIOC_QUERYMENU 

The VIDIOC_QUERYMENU documentation was not correct. EINVAL can be returned
if the driver does not support some of the menu items. I.e. in a list of
MPEG bitrates a driver generally supports only a subset of these.

This behavior has been in place for years, but was never properly documented.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Hans Verkuil 2010-09-11 11:38:51 -03:00 committed by Mauro Carvalho Chehab
parent 0827d0664d
commit 6756207a71
2 changed files with 12 additions and 9 deletions
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3
Documentation/DocBook/v4l/controls.xml
View File

@ -364,9 +364,6 @@ enumerate_menu (void)
querymenu.index++) {
if (0 == ioctl (fd, &VIDIOC-QUERYMENU;, &amp;querymenu)) {
printf (" %s\n", querymenu.name);
} else {
perror ("VIDIOC_QUERYMENU");
exit (EXIT_FAILURE);
}
}
}

18
Documentation/DocBook/v4l/vidioc-queryctrl.xml
View File

@ -103,8 +103,12 @@ structure. The driver fills the rest of the structure or returns an
<structfield>index</structfield> is invalid. Menu items are enumerated
by calling <constant>VIDIOC_QUERYMENU</constant> with successive
<structfield>index</structfield> values from &v4l2-queryctrl;
<structfield>minimum</structfield> (0) to
<structfield>maximum</structfield>, inclusive.</para>
<structfield>minimum</structfield> to
<structfield>maximum</structfield>, inclusive. Note that it is possible
for <constant>VIDIOC_QUERYMENU</constant> to return an &EINVAL; for some
indices between <structfield>minimum</structfield> and <structfield>maximum</structfield>.
In that case that particular menu item is not supported by this driver. Also note that
the <structfield>minimum</structfield> value is not necessarily 0.</para>
<para>See also the examples in <xref linkend="control" />.</para>
@ -139,7 +143,7 @@ string. This information is intended for the user.</entry>
<entry><structfield>minimum</structfield></entry>
<entry>Minimum value, inclusive. This field gives a lower
bound for <constant>V4L2_CTRL_TYPE_INTEGER</constant> controls and the
lowest valid index (always 0) for <constant>V4L2_CTRL_TYPE_MENU</constant> controls.
lowest valid index for <constant>V4L2_CTRL_TYPE_MENU</constant> controls.
For <constant>V4L2_CTRL_TYPE_STRING</constant> controls the minimum value
gives the minimum length of the string. This length <emphasis>does not include the terminating
zero</emphasis>. It may not be valid for any other type of control, including
@ -279,7 +283,7 @@ values which are actually different on the hardware.</entry>
</row>
<row>
<entry><constant>V4L2_CTRL_TYPE_MENU</constant></entry>
<entry>0</entry>
<entry>&ge; 0</entry>
<entry>1</entry>
<entry>N-1</entry>
<entry>The control has a menu of N choices. The names of
@ -405,8 +409,10 @@ writing a value will cause the device to carry out a given action
<term><errorcode>EINVAL</errorcode></term>
<listitem>
<para>The &v4l2-queryctrl; <structfield>id</structfield>
is invalid. The &v4l2-querymenu; <structfield>id</structfield> or
<structfield>index</structfield> is invalid.</para>
is invalid. The &v4l2-querymenu; <structfield>id</structfield> is
invalid or <structfield>index</structfield> is out of range (less than
<structfield>minimum</structfield> or greater than <structfield>maximum</structfield>)
or this particular menu item is not supported by the driver.</para>
</listitem>
</varlistentry>
<varlistentry>