Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 EST.
1 <refentry id="vidioc-prepare-buf"> 2 <refmeta> 3 <refentrytitle>ioctl VIDIOC_PREPARE_BUF</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>VIDIOC_PREPARE_BUF</refname> 9 <refpurpose>Prepare a buffer for I/O</refpurpose> 10 </refnamediv> 11 12 <refsynopsisdiv> 13 <funcsynopsis> 14 <funcprototype> 15 <funcdef>int <function>ioctl</function></funcdef> 16 <paramdef>int <parameter>fd</parameter></paramdef> 17 <paramdef>int <parameter>request</parameter></paramdef> 18 <paramdef>struct v4l2_buffer *<parameter>argp</parameter></paramdef> 19 </funcprototype> 20 </funcsynopsis> 21 </refsynopsisdiv> 22 23 <refsect1> 24 <title>Arguments</title> 25 26 <variablelist> 27 <varlistentry> 28 <term><parameter>fd</parameter></term> 29 <listitem> 30 <para>&fd;</para> 31 </listitem> 32 </varlistentry> 33 <varlistentry> 34 <term><parameter>request</parameter></term> 35 <listitem> 36 <para>VIDIOC_PREPARE_BUF</para> 37 </listitem> 38 </varlistentry> 39 <varlistentry> 40 <term><parameter>argp</parameter></term> 41 <listitem> 42 <para></para> 43 </listitem> 44 </varlistentry> 45 </variablelist> 46 </refsect1> 47 48 <refsect1> 49 <title>Description</title> 50 51 <para>Applications can optionally call the 52 <constant>VIDIOC_PREPARE_BUF</constant> ioctl to pass ownership of the buffer 53 to the driver before actually enqueuing it, using the 54 <constant>VIDIOC_QBUF</constant> ioctl, and to prepare it for future I/O. 55 Such preparations may include cache invalidation or cleaning. Performing them 56 in advance saves time during the actual I/O. In case such cache operations are 57 not required, the application can use one of 58 <constant>V4L2_BUF_FLAG_NO_CACHE_INVALIDATE</constant> and 59 <constant>V4L2_BUF_FLAG_NO_CACHE_CLEAN</constant> flags to skip the respective 60 step.</para> 61 62 <para>The <structname>v4l2_buffer</structname> structure is 63 specified in <xref linkend="buffer" />.</para> 64 </refsect1> 65 66 <refsect1> 67 &return-value; 68 69 <variablelist> 70 <varlistentry> 71 <term><errorcode>EBUSY</errorcode></term> 72 <listitem> 73 <para>File I/O is in progress.</para> 74 </listitem> 75 </varlistentry> 76 <varlistentry> 77 <term><errorcode>EINVAL</errorcode></term> 78 <listitem> 79 <para>The buffer <structfield>type</structfield> is not 80 supported, or the <structfield>index</structfield> is out of bounds, 81 or no buffers have been allocated yet, or the 82 <structfield>userptr</structfield> or 83 <structfield>length</structfield> are invalid.</para> 84 </listitem> 85 </varlistentry> 86 </variablelist> 87 </refsect1> 88 </refentry>
