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Diffstat (limited to 'Documentation/DocBook/v4l/func-ioctl.xml')
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diff --git a/Documentation/DocBook/v4l/func-ioctl.xml b/Documentation/DocBook/v4l/func-ioctl.xml new file mode 100644 index 00000000..b60fd37a --- /dev/null +++ b/Documentation/DocBook/v4l/func-ioctl.xml @@ -0,0 +1,145 @@ +<refentry id="func-ioctl"> + <refmeta> + <refentrytitle>V4L2 ioctl()</refentrytitle> + &manvol; + </refmeta> + + <refnamediv> + <refname>v4l2-ioctl</refname> + <refpurpose>Program a V4L2 device</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <funcsynopsis> + <funcsynopsisinfo>#include <sys/ioctl.h></funcsynopsisinfo> + <funcprototype> + <funcdef>int <function>ioctl</function></funcdef> + <paramdef>int <parameter>fd</parameter></paramdef> + <paramdef>int <parameter>request</parameter></paramdef> + <paramdef>void *<parameter>argp</parameter></paramdef> + </funcprototype> + </funcsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Arguments</title> + + <variablelist> + <varlistentry> + <term><parameter>fd</parameter></term> + <listitem> + <para>&fd;</para> + </listitem> + </varlistentry> + <varlistentry> + <term><parameter>request</parameter></term> + <listitem> + <para>V4L2 ioctl request code as defined in the <filename>videodev2.h</filename> header file, for example +VIDIOC_QUERYCAP.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><parameter>argp</parameter></term> + <listitem> + <para>Pointer to a function parameter, usually a structure.</para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>Description</title> + + <para>The <function>ioctl()</function> function is used to program +V4L2 devices. The argument <parameter>fd</parameter> must be an open +file descriptor. An ioctl <parameter>request</parameter> has encoded +in it whether the argument is an input, output or read/write +parameter, and the size of the argument <parameter>argp</parameter> in +bytes. Macros and defines specifying V4L2 ioctl requests are located +in the <filename>videodev2.h</filename> header file. +Applications should use their own copy, not include the version in the +kernel sources on the system they compile on. All V4L2 ioctl requests, +their respective function and parameters are specified in <xref + linkend="user-func" />.</para> + </refsect1> + + <refsect1> + <title>Return Value</title> + + <para>On success the <function>ioctl()</function> function returns +<returnvalue>0</returnvalue> and does not reset the +<varname>errno</varname> variable. On failure +<returnvalue>-1</returnvalue> is returned, when the ioctl takes an +output or read/write parameter it remains unmodified, and the +<varname>errno</varname> variable is set appropriately. See below for +possible error codes. Generic errors like <errorcode>EBADF</errorcode> +or <errorcode>EFAULT</errorcode> are not listed in the sections +discussing individual ioctl requests.</para> + <para>Note ioctls may return undefined error codes. Since errors +may have side effects such as a driver reset applications should +abort on unexpected errors.</para> + + <variablelist> + <varlistentry> + <term><errorcode>EBADF</errorcode></term> + <listitem> + <para><parameter>fd</parameter> is not a valid open file +descriptor.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><errorcode>EBUSY</errorcode></term> + <listitem> + <para>The property cannot be changed right now. Typically +this error code is returned when I/O is in progress or the driver +supports multiple opens and another process locked the property.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><errorcode>EFAULT</errorcode></term> + <listitem> + <para><parameter>argp</parameter> references an inaccessible +memory area.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><errorcode>ENOTTY</errorcode></term> + <listitem> + <para><parameter>fd</parameter> is not associated with a +character special device.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><errorcode>EINVAL</errorcode></term> + <listitem> + <para>The <parameter>request</parameter> or the data pointed +to by <parameter>argp</parameter> is not valid. This is a very common +error code, see the individual ioctl requests listed in <xref + linkend="user-func" /> for actual causes.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><errorcode>ENOMEM</errorcode></term> + <listitem> + <para>Not enough physical or virtual memory was available to +complete the request.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><errorcode>ERANGE</errorcode></term> + <listitem> + <para>The application attempted to set a control with the +&VIDIOC-S-CTRL; ioctl to a value which is out of bounds.</para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> +</refentry> + +<!-- +Local Variables: +mode: sgml +sgml-parent-document: "v4l2.sgml" +indent-tabs-mode: nil +End: +--> |