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Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-reqbufs.xml')
| -rw-r--r-- | Documentation/DocBook/media/v4l/vidioc-reqbufs.xml | 137 |
1 files changed, 0 insertions, 137 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-reqbufs.xml b/Documentation/DocBook/media/v4l/vidioc-reqbufs.xml deleted file mode 100644 index 0f193fda0..000000000 --- a/Documentation/DocBook/media/v4l/vidioc-reqbufs.xml +++ /dev/null @@ -1,137 +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>, -<link linkend="userp">user pointer</link> or <link -linkend="dmabuf">DMABUF</link> based 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. -Similarly, DMABUF buffers are allocated by applications through a device -driver, and this ioctl only configures the driver into DMABUF I/O mode without -performing any direct allocation.</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>__u32</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>__u32</entry> - <entry><structfield>memory</structfield></entry> - <entry>Applications set this field to -<constant>V4L2_MEMORY_MMAP</constant>, -<constant>V4L2_MEMORY_DMABUF</constant> or -<constant>V4L2_MEMORY_USERPTR</constant>. See <xref linkend="v4l2-memory" -/>.</entry> - </row> - <row> - <entry>__u32</entry> - <entry><structfield>reserved</structfield>[2]</entry> - <entry>A place holder for future extensions. Drivers and applications -must set the array to zero.</entry> - </row> - </tbody> - </tgroup> - </table> - </refsect1> - - <refsect1> - &return-value; - - <variablelist> - <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> |