89 lines
2.5 KiB
XML
89 lines
2.5 KiB
XML
<refentry id="vidioc-prepare-buf">
|
|
<refmeta>
|
|
<refentrytitle>ioctl VIDIOC_PREPARE_BUF</refentrytitle>
|
|
&manvol;
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>VIDIOC_PREPARE_BUF</refname>
|
|
<refpurpose>Prepare a buffer for 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_buffer *<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_PREPARE_BUF</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><parameter>argp</parameter></term>
|
|
<listitem>
|
|
<para></para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para>Applications can optionally call the
|
|
<constant>VIDIOC_PREPARE_BUF</constant> ioctl to pass ownership of the buffer
|
|
to the driver before actually enqueuing it, using the
|
|
<constant>VIDIOC_QBUF</constant> ioctl, and to prepare it for future I/O.
|
|
Such preparations may include cache invalidation or cleaning. Performing them
|
|
in advance saves time during the actual I/O. In case such cache operations are
|
|
not required, the application can use one of
|
|
<constant>V4L2_BUF_FLAG_NO_CACHE_INVALIDATE</constant> and
|
|
<constant>V4L2_BUF_FLAG_NO_CACHE_CLEAN</constant> flags to skip the respective
|
|
step.</para>
|
|
|
|
<para>The <structname>v4l2_buffer</structname> structure is
|
|
specified in <xref linkend="buffer" />.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
&return-value;
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><errorcode>EBUSY</errorcode></term>
|
|
<listitem>
|
|
<para>File I/O is in progress.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><errorcode>EINVAL</errorcode></term>
|
|
<listitem>
|
|
<para>The buffer <structfield>type</structfield> is not
|
|
supported, or the <structfield>index</structfield> is out of bounds,
|
|
or no buffers have been allocated yet, or the
|
|
<structfield>userptr</structfield> or
|
|
<structfield>length</structfield> are invalid.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
</refentry>
|