Based on kernel version 3.0.4. Page generated on 2011-10-03 22:07 EST.
1 <refentry id="vidioc-streamon"> 2 <refmeta> 3 <refentrytitle>ioctl VIDIOC_STREAMON, VIDIOC_STREAMOFF</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>VIDIOC_STREAMON</refname> 9 <refname>VIDIOC_STREAMOFF</refname> 10 <refpurpose>Start or stop streaming I/O</refpurpose> 11 </refnamediv> 12 13 <refsynopsisdiv> 14 <funcsynopsis> 15 <funcprototype> 16 <funcdef>int <function>ioctl</function></funcdef> 17 <paramdef>int <parameter>fd</parameter></paramdef> 18 <paramdef>int <parameter>request</parameter></paramdef> 19 <paramdef>const int *<parameter>argp</parameter></paramdef> 20 </funcprototype> 21 </funcsynopsis> 22 </refsynopsisdiv> 23 24 <refsect1> 25 <title>Arguments</title> 26 27 <variablelist> 28 <varlistentry> 29 <term><parameter>fd</parameter></term> 30 <listitem> 31 <para>&fd;</para> 32 </listitem> 33 </varlistentry> 34 <varlistentry> 35 <term><parameter>request</parameter></term> 36 <listitem> 37 <para>VIDIOC_STREAMON, VIDIOC_STREAMOFF</para> 38 </listitem> 39 </varlistentry> 40 <varlistentry> 41 <term><parameter>argp</parameter></term> 42 <listitem> 43 <para></para> 44 </listitem> 45 </varlistentry> 46 </variablelist> 47 </refsect1> 48 49 <refsect1> 50 <title>Description</title> 51 52 <para>The <constant>VIDIOC_STREAMON</constant> and 53 <constant>VIDIOC_STREAMOFF</constant> ioctl start and stop the capture 54 or output process during streaming (<link linkend="mmap">memory 55 mapping</link> or <link linkend="userp">user pointer</link>) I/O.</para> 56 57 <para>Specifically the capture hardware is disabled and no input 58 buffers are filled (if there are any empty buffers in the incoming 59 queue) until <constant>VIDIOC_STREAMON</constant> has been called. 60 Accordingly the output hardware is disabled, no video signal is 61 produced until <constant>VIDIOC_STREAMON</constant> has been called. 62 The ioctl will succeed only when at least one output buffer is in the 63 incoming queue.</para> 64 65 <para>The <constant>VIDIOC_STREAMOFF</constant> ioctl, apart of 66 aborting or finishing any DMA in progress, unlocks any user pointer 67 buffers locked in physical memory, and it removes all buffers from the 68 incoming and outgoing queues. That means all images captured but not 69 dequeued yet will be lost, likewise all images enqueued for output but 70 not transmitted yet. I/O returns to the same state as after calling 71 &VIDIOC-REQBUFS; and can be restarted accordingly.</para> 72 73 <para>Both ioctls take a pointer to an integer, the desired buffer or 74 stream type. This is the same as &v4l2-requestbuffers; 75 <structfield>type</structfield>.</para> 76 77 <para>Note applications can be preempted for unknown periods right 78 before or after the <constant>VIDIOC_STREAMON</constant> or 79 <constant>VIDIOC_STREAMOFF</constant> calls, there is no notion of 80 starting or stopping "now". Buffer timestamps can be used to 81 synchronize with other events.</para> 82 </refsect1> 83 84 <refsect1> 85 &return-value; 86 87 <variablelist> 88 <varlistentry> 89 <term><errorcode>EINVAL</errorcode></term> 90 <listitem> 91 <para>Streaming I/O is not supported, the buffer 92 <structfield>type</structfield> is not supported, or no buffers have 93 been allocated (memory mapping) or enqueued (output) yet.</para> 94 </listitem> 95 </varlistentry> 96 <varlistentry> 97 <term><errorcode>EPIPE</errorcode></term> 98 <listitem> 99 <para>The driver implements <link 100 linkend="pad-level-formats">pad-level format configuration</link> and 101 the pipeline configuration is invalid. 102 </para> 103 </listitem> 104 </varlistentry> 105 </variablelist> 106 </refsect1> 107 </refentry> 108 109 <!-- 110 Local Variables: 111 mode: sgml 112 sgml-parent-document: "v4l2.sgml" 113 indent-tabs-mode: nil 114 End: 115 -->
