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71 lines
2.2 KiB
71 lines
2.2 KiB
<refentry id="func-ioctl">
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<refmeta>
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<refentrytitle>V4L2 ioctl()</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>v4l2-ioctl</refname>
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<refpurpose>Program a V4L2 device</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <sys/ioctl.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>void *<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Arguments</title>
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<variablelist>
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<varlistentry>
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<term><parameter>fd</parameter></term>
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<listitem>
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<para>&fd;</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>request</parameter></term>
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<listitem>
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<para>V4L2 ioctl request code as defined in the <filename>videodev2.h</filename> header file, for example
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VIDIOC_QUERYCAP.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>argp</parameter></term>
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<listitem>
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<para>Pointer to a function parameter, usually a structure.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Description</title>
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<para>The <function>ioctl()</function> function is used to program
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V4L2 devices. The argument <parameter>fd</parameter> must be an open
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file descriptor. An ioctl <parameter>request</parameter> has encoded
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in it whether the argument is an input, output or read/write
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parameter, and the size of the argument <parameter>argp</parameter> in
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bytes. Macros and defines specifying V4L2 ioctl requests are located
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in the <filename>videodev2.h</filename> header file.
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Applications should use their own copy, not include the version in the
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kernel sources on the system they compile on. All V4L2 ioctl requests,
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their respective function and parameters are specified in <xref
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linkend="user-func" />.</para>
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</refsect1>
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<refsect1>
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&return-value;
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<para>When an ioctl that takes an output or read/write parameter fails,
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the parameter remains unmodified.</para>
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</refsect1>
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</refentry>
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