[media] media: Links setup

Create the following ioctl and implement it at the media device level to
setup links.

- MEDIA_IOC_SETUP_LINK: Modify the properties of a given link

The only property that can currently be modified is the ENABLED link
flag to enable/disable a link. Links marked with the IMMUTABLE link flag
can not be enabled or disabled.

Enabling or disabling a link has effects on entities' use count. Those
changes are automatically propagated through the graph.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Stanimir Varbanov <svarbanov@mm-sol.com>
Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 91 insertions, 0 deletions

diff --git a/Documentation/DocBook/v4l/media-controller.xml b/Documentation/DocBook/v4l/media-controller.xml
index 2c4fd2b27683..2dc25e1d4089 100644
--- a/Documentation/DocBook/v4l/media-controller.xml
+++ b/Documentation/DocBook/v4l/media-controller.xml
@@ -85,4 +85,5 @@
   &sub-media-ioc-device-info;
   &sub-media-ioc-enum-entities;
   &sub-media-ioc-enum-links;
+  &sub-media-ioc-setup-link;
 </appendix>
diff --git a/Documentation/DocBook/v4l/media-ioc-setup-link.xml b/Documentation/DocBook/v4l/media-ioc-setup-link.xml
new file mode 100644
index 000000000000..09ab3d2b3a52
--- /dev/null
+++ b/Documentation/DocBook/v4l/media-ioc-setup-link.xml
@@ -0,0 +1,90 @@
+<refentry id="media-ioc-setup-link">
+  <refmeta>
+    <refentrytitle>ioctl MEDIA_IOC_SETUP_LINK</refentrytitle>
+    &manvol;
+  </refmeta>
+
+  <refnamediv>
+    <refname>MEDIA_IOC_SETUP_LINK</refname>
+    <refpurpose>Modify the properties of a link</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 media_link_desc *<parameter>argp</parameter></paramdef>
+      </funcprototype>
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Arguments</title>
+
+    <variablelist>
+      <varlistentry>
+	<term><parameter>fd</parameter></term>
+	<listitem>
+	  <para>File descriptor returned by
+	  <link linkend='media-func-open'><function>open()</function></link>.</para>
+	</listitem>
+      </varlistentry>
+      <varlistentry>
+	<term><parameter>request</parameter></term>
+	<listitem>
+	  <para>MEDIA_IOC_ENUM_LINKS</para>
+	</listitem>
+      </varlistentry>
+      <varlistentry>
+	<term><parameter>argp</parameter></term>
+	<listitem>
+	  <para></para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para>To change link properties applications fill a &media-link-desc; with
+    link identification information (source and sink pad) and the new requested
+    link flags. They then call the MEDIA_IOC_SETUP_LINK ioctl with a pointer to
+    that structure.</para>
+    <para>The only configurable property is the <constant>ENABLED</constant>
+    link flag to enable/disable a link. Links marked with the
+    <constant>IMMUTABLE</constant> link flag can not be enabled or disabled.
+    </para>
+    <para>Link configuration has no side effect on other links. If an enabled
+    link at the sink pad prevents the link from being enabled, the driver
+    returns with an &EBUSY;.</para>
+    <para>If the specified link can't be found the driver returns with an
+    &EINVAL;.</para>
+  </refsect1>
+
+  <refsect1>
+    &return-value;
+
+    <variablelist>
+      <varlistentry>
+	<term><errorcode>EBUSY</errorcode></term>
+	<listitem>
+	  <para>The link properties can't be changed because the link is
+	  currently busy. This can be caused, for instance, by an active media
+	  stream (audio or video) on the link. The ioctl shouldn't be retried if
+	  no other action is performed before to fix the problem.</para>
+	</listitem>
+      </varlistentry>
+      <varlistentry>
+	<term><errorcode>EINVAL</errorcode></term>
+	<listitem>
+	  <para>The &media-link-desc; references a non-existing link, or the
+	  link is immutable and an attempt to modify its configuration was made.
+	  </para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+</refentry>