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As Rupert pointed out, the phrase "It is good practice" should be replaced with "You must". Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Cc: Rupert Eibauer <Rupert.Eibauer@ces.ch> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
86 lines
2.4 KiB
XML
86 lines
2.4 KiB
XML
<refentry id="vidioc-g-output">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_G_OUTPUT</refname>
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<refname>VIDIOC_S_OUTPUT</refname>
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<refpurpose>Query or select the current video output</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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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>int *<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>VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT</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></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>To query the current video output applications call the
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<constant>VIDIOC_G_OUTPUT</constant> ioctl with a pointer to an integer
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where the driver stores the number of the output, as in the
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&v4l2-output; <structfield>index</structfield> field. This ioctl
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will fail only when there are no video outputs, returning the
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&EINVAL;.</para>
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<para>To select a video output applications store the number of the
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desired output in an integer and call the
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<constant>VIDIOC_S_OUTPUT</constant> ioctl with a pointer to this integer.
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Side effects are possible. For example outputs may support different
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video standards, so the driver may implicitly switch the current
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standard.
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standard. Because of these possible side effects applications
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must select an output before querying or negotiating any other parameters.</para>
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<para>Information about video outputs is available using the
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&VIDIOC-ENUMOUTPUT; ioctl.</para>
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</refsect1>
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<refsect1>
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&return-value;
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<variablelist>
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<varlistentry>
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<term><errorcode>EINVAL</errorcode></term>
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<listitem>
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<para>The number of the video output is out of bounds, or
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there are no video outputs at all.</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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</refentry>
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