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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>
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