Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / Documentation / DocBook / media / v4l / vidioc-streamon.xml

diff --git a/kernel/Documentation/DocBook/media/v4l/vidioc-streamon.xml b/kernel/Documentation/DocBook/media/v4l/vidioc-streamon.xml
new file mode 100644 (file)
index 0000000..df2c63d
--- /dev/null
+++ b/kernel/Documentation/DocBook/media/v4l/vidioc-streamon.xml
@@ -0,0 +1,128 @@
+<refentry id="vidioc-streamon">
+  <refmeta>
+    <refentrytitle>ioctl VIDIOC_STREAMON, VIDIOC_STREAMOFF</refentrytitle>
+    &manvol;
+  </refmeta>
+
+  <refnamediv>
+    <refname>VIDIOC_STREAMON</refname>
+    <refname>VIDIOC_STREAMOFF</refname>
+    <refpurpose>Start or stop streaming 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>const int *<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_STREAMON, VIDIOC_STREAMOFF</para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term><parameter>argp</parameter></term>
+       <listitem>
+         <para></para>
+       </listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para>The <constant>VIDIOC_STREAMON</constant> and
+<constant>VIDIOC_STREAMOFF</constant> ioctl start and stop the capture
+or output process during streaming (<link linkend="mmap">memory
+mapping</link>, <link linkend="userp">user pointer</link> or
+<link linkend="dmabuf">DMABUF</link>) I/O.</para>
+
+    <para>Capture hardware is disabled and no input
+buffers are filled (if there are any empty buffers in the incoming
+queue) until <constant>VIDIOC_STREAMON</constant> has been called.
+Output hardware is disabled and no video signal is
+produced until <constant>VIDIOC_STREAMON</constant> has been called.
+The ioctl will succeed when at least one output buffer is in the
+incoming queue.</para>
+
+    <para>Memory-to-memory devices will not start until
+<constant>VIDIOC_STREAMON</constant> has been called for both the capture
+and output stream types.</para>
+
+    <para>If <constant>VIDIOC_STREAMON</constant> fails then any already
+queued buffers will remain queued.</para>
+
+    <para>The <constant>VIDIOC_STREAMOFF</constant> ioctl, apart of
+aborting or finishing any DMA in progress, unlocks any user pointer
+buffers locked in physical memory, and it removes all buffers from the
+incoming and outgoing queues. That means all images captured but not
+dequeued yet will be lost, likewise all images enqueued for output but
+not transmitted yet. I/O returns to the same state as after calling
+&VIDIOC-REQBUFS; and can be restarted accordingly.</para>
+
+    <para>If buffers have been queued with &VIDIOC-QBUF; and
+<constant>VIDIOC_STREAMOFF</constant> is called without ever having
+called <constant>VIDIOC_STREAMON</constant>, then those queued buffers
+will also be removed from the incoming queue and all are returned to the
+same state as after calling &VIDIOC-REQBUFS; and can be restarted
+accordingly.</para>
+
+    <para>Both ioctls take a pointer to an integer, the desired buffer or
+stream type. This is the same as &v4l2-requestbuffers;
+<structfield>type</structfield>.</para>
+
+    <para>If <constant>VIDIOC_STREAMON</constant> is called when streaming
+is already in progress, or if <constant>VIDIOC_STREAMOFF</constant> is called
+when streaming is already stopped, then 0 is returned. Nothing happens in the
+case of <constant>VIDIOC_STREAMON</constant>, but <constant>VIDIOC_STREAMOFF</constant>
+will return queued buffers to their starting state as mentioned above.</para>
+
+    <para>Note that applications can be preempted for unknown periods right
+before or after the <constant>VIDIOC_STREAMON</constant> or
+<constant>VIDIOC_STREAMOFF</constant> calls, there is no notion of
+starting or stopping "now". Buffer timestamps can be used to
+synchronize with other events.</para>
+  </refsect1>
+
+  <refsect1>
+    &return-value;
+
+    <variablelist>
+      <varlistentry>
+       <term><errorcode>EINVAL</errorcode></term>
+       <listitem>
+         <para>The buffer <structfield>type</structfield> is not supported,
+         or no buffers have been allocated (memory mapping) or enqueued
+         (output) yet.</para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term><errorcode>EPIPE</errorcode></term>
+       <listitem>
+         <para>The driver implements <link
+         linkend="pad-level-formats">pad-level format configuration</link> and
+         the pipeline configuration is invalid.
+         </para>
+       </listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+</refentry>