283 строки
8.7 KiB
XML
283 строки
8.7 KiB
XML
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<refentry id="vidioc-enum-framesizes">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_ENUM_FRAMESIZES</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_ENUM_FRAMESIZES</refname>
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<refpurpose>Enumerate frame sizes</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>struct v4l2_frmsizeenum *<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_ENUM_FRAMESIZES</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 &v4l2-frmsizeenum; that contains an index
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and pixel format and receives a frame width and height.</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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<note>
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<title>Experimental</title>
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<para>This is an <link linkend="experimental">experimental</link>
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interface and may change in the future.</para>
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</note>
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<para>This ioctl allows applications to enumerate all frame sizes
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(&ie; width and height in pixels) that the device supports for the
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given pixel format.</para>
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<para>The supported pixel formats can be obtained by using the
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&VIDIOC-ENUM-FMT; function.</para>
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<para>The return value and the content of the
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<structfield>v4l2_frmsizeenum.type</structfield> field depend on the
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type of frame sizes the device supports. Here are the semantics of the
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function for the different cases:</para>
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<itemizedlist>
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<listitem>
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<para><emphasis role="bold">Discrete:</emphasis> The function
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returns success if the given index value (zero-based) is valid. The
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application should increase the index by one for each call until
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<constant>EINVAL</constant> is returned. The
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<structfield>v4l2_frmsizeenum.type</structfield> field is set to
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<constant>V4L2_FRMSIZE_TYPE_DISCRETE</constant> by the driver. Of the
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union only the <structfield>discrete</structfield> member is
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valid.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Step-wise:</emphasis> The function
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returns success if the given index value is zero and
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<constant>EINVAL</constant> for any other index value. The
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<structfield>v4l2_frmsizeenum.type</structfield> field is set to
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<constant>V4L2_FRMSIZE_TYPE_STEPWISE</constant> by the driver. Of the
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union only the <structfield>stepwise</structfield> member is
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valid.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Continuous:</emphasis> This is a
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special case of the step-wise type above. The function returns success
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if the given index value is zero and <constant>EINVAL</constant> for
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any other index value. The
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<structfield>v4l2_frmsizeenum.type</structfield> field is set to
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<constant>V4L2_FRMSIZE_TYPE_CONTINUOUS</constant> by the driver. Of
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the union only the <structfield>stepwise</structfield> member is valid
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and the <structfield>step_width</structfield> and
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<structfield>step_height</structfield> values are set to 1.</para>
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</listitem>
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</itemizedlist>
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<para>When the application calls the function with index zero, it
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must check the <structfield>type</structfield> field to determine the
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type of frame size enumeration the device supports. Only for the
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<constant>V4L2_FRMSIZE_TYPE_DISCRETE</constant> type does it make
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sense to increase the index value to receive more frame sizes.</para>
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<para>Note that the order in which the frame sizes are returned
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has no special meaning. In particular does it not say anything about
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potential default format sizes.</para>
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<para>Applications can assume that the enumeration data does not
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change without any interaction from the application itself. This means
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that the enumeration data is consistent if the application does not
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perform any other ioctl calls while it runs the frame size
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enumeration.</para>
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</refsect1>
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<refsect1>
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<title>Structs</title>
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<para>In the structs below, <emphasis>IN</emphasis> denotes a
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value that has to be filled in by the application,
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<emphasis>OUT</emphasis> denotes values that the driver fills in. The
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application should zero out all members except for the
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<emphasis>IN</emphasis> fields.</para>
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<table pgwide="1" frame="none" id="v4l2-frmsize-discrete">
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<title>struct <structname>v4l2_frmsize_discrete</structname></title>
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<tgroup cols="3">
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&cs-str;
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<tbody valign="top">
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<row>
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<entry>__u32</entry>
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<entry><structfield>width</structfield></entry>
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<entry>Width of the frame [pixel].</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>height</structfield></entry>
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<entry>Height of the frame [pixel].</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<table pgwide="1" frame="none" id="v4l2-frmsize-stepwise">
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<title>struct <structname>v4l2_frmsize_stepwise</structname></title>
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<tgroup cols="3">
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&cs-str;
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<tbody valign="top">
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<row>
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<entry>__u32</entry>
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<entry><structfield>min_width</structfield></entry>
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<entry>Minimum frame width [pixel].</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>max_width</structfield></entry>
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<entry>Maximum frame width [pixel].</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>step_width</structfield></entry>
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<entry>Frame width step size [pixel].</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>min_height</structfield></entry>
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<entry>Minimum frame height [pixel].</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>max_height</structfield></entry>
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<entry>Maximum frame height [pixel].</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>step_height</structfield></entry>
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<entry>Frame height step size [pixel].</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<table pgwide="1" frame="none" id="v4l2-frmsizeenum">
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<title>struct <structname>v4l2_frmsizeenum</structname></title>
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<tgroup cols="4">
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<colspec colname="c1" />
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<colspec colname="c2" />
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<colspec colname="c3" />
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<colspec colname="c4" />
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<tbody valign="top">
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<row>
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<entry>__u32</entry>
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<entry><structfield>index</structfield></entry>
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<entry></entry>
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<entry>IN: Index of the given frame size in the enumeration.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>pixel_format</structfield></entry>
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<entry></entry>
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<entry>IN: Pixel format for which the frame sizes are enumerated.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>type</structfield></entry>
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<entry></entry>
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<entry>OUT: Frame size type the device supports.</entry>
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</row>
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<row>
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<entry>union</entry>
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<entry></entry>
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<entry></entry>
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<entry>OUT: Frame size with the given index.</entry>
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</row>
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<row>
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<entry></entry>
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<entry>&v4l2-frmsize-discrete;</entry>
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<entry><structfield>discrete</structfield></entry>
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<entry></entry>
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</row>
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<row>
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<entry></entry>
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<entry>&v4l2-frmsize-stepwise;</entry>
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<entry><structfield>stepwise</structfield></entry>
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<entry></entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>reserved[2]</structfield></entry>
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<entry></entry>
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<entry>Reserved space for future use.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</refsect1>
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<refsect1>
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<title>Enums</title>
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<table pgwide="1" frame="none" id="v4l2-frmsizetypes">
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<title>enum <structname>v4l2_frmsizetypes</structname></title>
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<tgroup cols="3">
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&cs-def;
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<tbody valign="top">
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<row>
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<entry><constant>V4L2_FRMSIZE_TYPE_DISCRETE</constant></entry>
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<entry>1</entry>
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<entry>Discrete frame size.</entry>
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</row>
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<row>
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<entry><constant>V4L2_FRMSIZE_TYPE_CONTINUOUS</constant></entry>
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<entry>2</entry>
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<entry>Continuous frame size.</entry>
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</row>
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<row>
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<entry><constant>V4L2_FRMSIZE_TYPE_STEPWISE</constant></entry>
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<entry>3</entry>
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<entry>Step-wise defined frame size.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</refsect1>
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<refsect1>
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&return-value;
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<para>See the description section above for a list of return
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values that <varname>errno</varname> can have.</para>
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</refsect1>
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</refentry>
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<!--
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Local Variables:
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mode: sgml
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sgml-parent-document: "v4l2.sgml"
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indent-tabs-mode: nil
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End:
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-->
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