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Diffstat (limited to 'Documentation/DocBook/v4l/vidioc-reqbufs.xml')
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1 files changed, 0 insertions, 150 deletions
diff --git a/Documentation/DocBook/v4l/vidioc-reqbufs.xml b/Documentation/DocBook/v4l/vidioc-reqbufs.xml deleted file mode 100644 index 69800ae..0000000 --- a/Documentation/DocBook/v4l/vidioc-reqbufs.xml +++ /dev/null @@ -1,150 +0,0 @@ -<refentry id="vidioc-reqbufs"> - <refmeta> - <refentrytitle>ioctl VIDIOC_REQBUFS</refentrytitle> - &manvol; - </refmeta> - - <refnamediv> - <refname>VIDIOC_REQBUFS</refname> - <refpurpose>Initiate Memory Mapping or User Pointer I/O</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_requestbuffers *<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_REQBUFS</para> - </listitem> - </varlistentry> - <varlistentry> - <term><parameter>argp</parameter></term> - <listitem> - <para></para> - </listitem> - </varlistentry> - </variablelist> - </refsect1> - - <refsect1> - <title>Description</title> - - <para>This ioctl is used to initiate <link linkend="mmap">memory -mapped</link> or <link linkend="userp">user pointer</link> -I/O. Memory mapped buffers are located in device memory and must be -allocated with this ioctl before they can be mapped into the -application's address space. User buffers are allocated by -applications themselves, and this ioctl is merely used to switch the -driver into user pointer I/O mode and to setup some internal structures.</para> - - <para>To allocate device buffers applications initialize all -fields of the <structname>v4l2_requestbuffers</structname> structure. -They set the <structfield>type</structfield> field to the respective -stream or buffer type, the <structfield>count</structfield> field to -the desired number of buffers, <structfield>memory</structfield> -must be set to the requested I/O method and the <structfield>reserved</structfield> array -must be zeroed. When the ioctl -is called with a pointer to this structure the driver will attempt to allocate -the requested number of buffers and it stores the actual number -allocated in the <structfield>count</structfield> field. It can be -smaller than the number requested, even zero, when the driver runs out -of free memory. A larger number is also possible when the driver requires -more buffers to function correctly. For example video output requires at least two buffers, -one displayed and one filled by the application.</para> - <para>When the I/O method is not supported the ioctl -returns an &EINVAL;.</para> - - <para>Applications can call <constant>VIDIOC_REQBUFS</constant> -again to change the number of buffers, however this cannot succeed -when any buffers are still mapped. A <structfield>count</structfield> -value of zero frees all buffers, after aborting or finishing any DMA -in progress, an implicit &VIDIOC-STREAMOFF;. <!-- mhs: I see no -reason why munmap()ping one or even all buffers must imply -streamoff.--></para> - - <table pgwide="1" frame="none" id="v4l2-requestbuffers"> - <title>struct <structname>v4l2_requestbuffers</structname></title> - <tgroup cols="3"> - &cs-str; - <tbody valign="top"> - <row> - <entry>__u32</entry> - <entry><structfield>count</structfield></entry> - <entry>The number of buffers requested or granted.</entry> - </row> - <row> - <entry>&v4l2-buf-type;</entry> - <entry><structfield>type</structfield></entry> - <entry>Type of the stream or buffers, this is the same -as the &v4l2-format; <structfield>type</structfield> field. See <xref - linkend="v4l2-buf-type" /> for valid values.</entry> - </row> - <row> - <entry>&v4l2-memory;</entry> - <entry><structfield>memory</structfield></entry> - <entry>Applications set this field to -<constant>V4L2_MEMORY_MMAP</constant> or -<constant>V4L2_MEMORY_USERPTR</constant>.</entry> - </row> - <row> - <entry>__u32</entry> - <entry><structfield>reserved</structfield>[2]</entry> - <entry>A place holder for future extensions and custom -(driver defined) buffer types <constant>V4L2_BUF_TYPE_PRIVATE</constant> and -higher. This array should be zeroed by applications.</entry> - </row> - </tbody> - </tgroup> - </table> - </refsect1> - - <refsect1> - &return-value; - - <variablelist> - <varlistentry> - <term><errorcode>EBUSY</errorcode></term> - <listitem> - <para>The driver supports multiple opens and I/O is already -in progress, or reallocation of buffers was attempted although one or -more are still mapped.</para> - </listitem> - </varlistentry> - <varlistentry> - <term><errorcode>EINVAL</errorcode></term> - <listitem> - <para>The buffer type (<structfield>type</structfield> field) or the -requested I/O method (<structfield>memory</structfield>) is not -supported.</para> - </listitem> - </varlistentry> - </variablelist> - </refsect1> -</refentry> - -<!-- -Local Variables: -mode: sgml -sgml-parent-document: "v4l2.sgml" -indent-tabs-mode: nil -End: ---> |