140d88165c
Create the following ioctl and implement it at the media device level to query device information. - MEDIA_IOC_DEVICE_INFO: Query media device information The ioctl and its data structure are defined in the new kernel header linux/media.h available to userspace applications. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Acked-by: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
117 lines
3.7 KiB
XML
117 lines
3.7 KiB
XML
<refentry id="media-func-ioctl">
|
|
<refmeta>
|
|
<refentrytitle>media ioctl()</refentrytitle>
|
|
&manvol;
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>media-ioctl</refname>
|
|
<refpurpose>Control a media 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>Media ioctl request code as defined in the media.h header file,
|
|
for example MEDIA_IOC_SETUP_LINK.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><parameter>argp</parameter></term>
|
|
<listitem>
|
|
<para>Pointer to a request-specific structure.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
<para>The <function>ioctl()</function> function manipulates media device
|
|
parameters. The argument <parameter>fd</parameter> must be an open file
|
|
descriptor.</para>
|
|
<para>The ioctl <parameter>request</parameter> code specifies the media
|
|
function to be called. It 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.</para>
|
|
<para>Macros and structures definitions specifying media ioctl requests and
|
|
their parameters are located in the media.h header file. All media ioctl
|
|
requests, their respective function and parameters are specified in
|
|
<xref linkend="media-user-func" />.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Return Value</title>
|
|
|
|
<para><function>ioctl()</function> returns <returnvalue>0</returnvalue> on
|
|
success. On failure, <returnvalue>-1</returnvalue> is returned, and the
|
|
<varname>errno</varname> variable is set appropriately. Generic error codes
|
|
are listed below, and request-specific error codes are listed in the
|
|
individual requests descriptions.</para>
|
|
<para>When an ioctl that takes an output or read/write parameter fails,
|
|
the parameter remains unmodified.</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>EFAULT</errorcode></term>
|
|
<listitem>
|
|
<para><parameter>argp</parameter> references an inaccessible memory
|
|
area.</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="media-user-func" /> for actual causes.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><errorcode>ENOMEM</errorcode></term>
|
|
<listitem>
|
|
<para>Insufficient kernel memory was available to complete the
|
|
request.</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>
|
|
</variablelist>
|
|
</refsect1>
|
|
</refentry>
|