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authorLinus Torvalds <torvalds@linux-foundation.org>2009-09-21 09:03:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-21 09:03:10 -0700
commitc720f5655df159a630fa0290a0bd67c93e92b0bf (patch)
tree940d139d0ec1ff5201efddef6cc663166a8a2df3 /Documentation/DocBook/v4l/vidioc-g-fmt.xml
parent33e6c1a0de818d3698cdab27c42915661011319d (diff)
parent84d6ae431f315e8973aac3c3fe1d550fc9240ef3 (diff)
downloadblackbird-op-linux-c720f5655df159a630fa0290a0bd67c93e92b0bf.tar.gz
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Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6: (222 commits) V4L/DVB (13033): pt1: Don't use a deprecated DMA_BIT_MASK macro V4L/DVB (13029): radio-si4713: remove #include <linux/version.h> V4L/DVB (13027): go7007: convert printks to v4l2_info V4L/DVB (13026): s2250-board: Implement brightness and contrast controls V4L/DVB (13025): s2250-board: Fix memory leaks V4L/DVB (13024): go7007: Implement vidioc_g_std and vidioc_querystd V4L/DVB (13023): go7007: Merge struct gofh and go declarations V4L/DVB (13022): go7007: Fix mpeg controls V4L/DVB (13021): go7007: Fix whitespace and line lengths V4L/DVB (13020): go7007: Updates to Kconfig and Makefile V4L/DVB (13019): video: initial support for ADV7180 V4L/DVB (13018): kzalloc failure ignored in au8522_probe() V4L/DVB (13017): gspca: kmalloc failure ignored in sd_start() V4L/DVB (13016): kmalloc failure ignored in lgdt3304_attach() and s921_attach() V4L/DVB (13015): kmalloc failure ignored in m920x_firmware_download() V4L/DVB (13014): Add support for Compro VideoMate E800 (DVB-T part only) V4L/DVB (13013): FM TX: si4713: Kconfig: Fixed two typos. V4L/DVB (13012): uvc: introduce missing kfree V4L/DVB (13011): Change tuner type of BeholdTV cards V4L/DVB (13009): gspca - stv06xx-hdcs: Reduce exposure range ...
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+<refentry id="vidioc-g-fmt">
+ <refmeta>
+ <refentrytitle>ioctl VIDIOC_G_FMT, VIDIOC_S_FMT,
+VIDIOC_TRY_FMT</refentrytitle>
+ &manvol;
+ </refmeta>
+
+ <refnamediv>
+ <refname>VIDIOC_G_FMT</refname>
+ <refname>VIDIOC_S_FMT</refname>
+ <refname>VIDIOC_TRY_FMT</refname>
+ <refpurpose>Get or set the data format, try a format</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcprototype>
+ <funcdef>int <function>ioctl</function></funcdef>
+ <paramdef>int <parameter>fd</parameter></paramdef>
+ <paramdef>int <parameter>request</parameter></paramdef>
+ <paramdef>struct v4l2_format
+*<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>VIDIOC_G_FMT, VIDIOC_S_FMT, VIDIOC_TRY_FMT</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>argp</parameter></term>
+ <listitem>
+ <para></para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>These ioctls are used to negotiate the format of data
+(typically image format) exchanged between driver and
+application.</para>
+
+ <para>To query the current parameters applications set the
+<structfield>type</structfield> field of a struct
+<structname>v4l2_format</structname> to the respective buffer (stream)
+type. For example video capture devices use
+<constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>. When the application
+calls the <constant>VIDIOC_G_FMT</constant> ioctl with a pointer to
+this structure the driver fills the respective member of the
+<structfield>fmt</structfield> union. In case of video capture devices
+that is the &v4l2-pix-format; <structfield>pix</structfield> member.
+When the requested buffer type is not supported drivers return an
+&EINVAL;.</para>
+
+ <para>To change the current format parameters applications
+initialize the <structfield>type</structfield> field and all
+fields of the respective <structfield>fmt</structfield>
+union member. For details see the documentation of the various devices
+types in <xref linkend="devices" />. Good practice is to query the
+current parameters first, and to
+modify only those parameters not suitable for the application. When
+the application calls the <constant>VIDIOC_S_FMT</constant> ioctl
+with a pointer to a <structname>v4l2_format</structname> structure
+the driver checks
+and adjusts the parameters against hardware abilities. Drivers
+should not return an error code unless the input is ambiguous, this is
+a mechanism to fathom device capabilities and to approach parameters
+acceptable for both the application and driver. On success the driver
+may program the hardware, allocate resources and generally prepare for
+data exchange.
+Finally the <constant>VIDIOC_S_FMT</constant> ioctl returns the
+current format parameters as <constant>VIDIOC_G_FMT</constant> does.
+Very simple, inflexible devices may even ignore all input and always
+return the default parameters. However all V4L2 devices exchanging
+data with the application must implement the
+<constant>VIDIOC_G_FMT</constant> and
+<constant>VIDIOC_S_FMT</constant> ioctl. When the requested buffer
+type is not supported drivers return an &EINVAL; on a
+<constant>VIDIOC_S_FMT</constant> attempt. When I/O is already in
+progress or the resource is not available for other reasons drivers
+return the &EBUSY;.</para>
+
+ <para>The <constant>VIDIOC_TRY_FMT</constant> ioctl is equivalent
+to <constant>VIDIOC_S_FMT</constant> with one exception: it does not
+change driver state. It can also be called at any time, never
+returning <errorcode>EBUSY</errorcode>. This function is provided to
+negotiate parameters, to learn about hardware limitations, without
+disabling I/O or possibly time consuming hardware preparations.
+Although strongly recommended drivers are not required to implement
+this ioctl.</para>
+
+ <table pgwide="1" frame="none" id="v4l2-format">
+ <title>struct <structname>v4l2_format</structname></title>
+ <tgroup cols="4">
+ <colspec colname="c1" />
+ <colspec colname="c2" />
+ <colspec colname="c3" />
+ <colspec colname="c4" />
+ <tbody valign="top">
+ <row>
+ <entry>&v4l2-buf-type;</entry>
+ <entry><structfield>type</structfield></entry>
+ <entry></entry>
+ <entry>Type of the data stream, see <xref
+ linkend="v4l2-buf-type" />.</entry>
+ </row>
+ <row>
+ <entry>union</entry>
+ <entry><structfield>fmt</structfield></entry>
+ </row>
+ <row>
+ <entry></entry>
+ <entry>&v4l2-pix-format;</entry>
+ <entry><structfield>pix</structfield></entry>
+ <entry>Definition of an image format, see <xref
+ linkend="pixfmt" />, used by video capture and output
+devices.</entry>
+ </row>
+ <row>
+ <entry></entry>
+ <entry>&v4l2-window;</entry>
+ <entry><structfield>win</structfield></entry>
+ <entry>Definition of an overlaid image, see <xref
+ linkend="overlay" />, used by video overlay devices.</entry>
+ </row>
+ <row>
+ <entry></entry>
+ <entry>&v4l2-vbi-format;</entry>
+ <entry><structfield>vbi</structfield></entry>
+ <entry>Raw VBI capture or output parameters. This is
+discussed in more detail in <xref linkend="raw-vbi" />. Used by raw VBI
+capture and output devices.</entry>
+ </row>
+ <row>
+ <entry></entry>
+ <entry>&v4l2-sliced-vbi-format;</entry>
+ <entry><structfield>sliced</structfield></entry>
+ <entry>Sliced VBI capture or output parameters. See
+<xref linkend="sliced" /> for details. Used by sliced VBI
+capture and output devices.</entry>
+ </row>
+ <row>
+ <entry></entry>
+ <entry>__u8</entry>
+ <entry><structfield>raw_data</structfield>[200]</entry>
+ <entry>Place holder for future extensions and custom
+(driver defined) formats with <structfield>type</structfield>
+<constant>V4L2_BUF_TYPE_PRIVATE</constant> and higher.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </refsect1>
+
+ <refsect1>
+ &return-value;
+
+ <variablelist>
+ <varlistentry>
+ <term><errorcode>EBUSY</errorcode></term>
+ <listitem>
+ <para>The data format cannot be changed at this
+time, for example because I/O is already in progress.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorcode>EINVAL</errorcode></term>
+ <listitem>
+ <para>The &v4l2-format; <structfield>type</structfield>
+field is invalid, the requested buffer type not supported, or
+<constant>VIDIOC_TRY_FMT</constant> was called and is not
+supported with this buffer type.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+</refentry>
+
+<!--
+Local Variables:
+mode: sgml
+sgml-parent-document: "v4l2.sgml"
+indent-tabs-mode: nil
+End:
+-->
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