[media] v4l: v4l2_subdev userspace format API

Add a userspace API to get, set and enumerate the media format on a
subdev pad.

The format at the output of a subdev usually depends on the format at
its input(s). The try format operation is thus not suitable for probing
format at individual pads, as it can't modify the device state and thus
can't remember the format tried at the input to compute the output
format.

To fix the problem, pass an extra argument to the get/set format
operations to select the 'try' or 'active' format.

The try format is used when probing the subdev. Setting the try format
must not change the device configuration but can store data for later
reuse. Data storage is provided at the file-handle level so applications
probing the subdev concurently won't interfere with each other.

The active format is used when configuring the subdev. It's identical to
the format handled by the usual get/set operations.

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>

1 files changed, 119 insertions, 0 deletions

diff --git a/Documentation/DocBook/v4l/vidioc-subdev-enum-mbus-code.xml b/Documentation/DocBook/v4l/vidioc-subdev-enum-mbus-code.xml
new file mode 100644
index 000000000000..a6b3432449f6
--- /dev/null
+++ b/Documentation/DocBook/v4l/vidioc-subdev-enum-mbus-code.xml
@@ -0,0 +1,119 @@
+<refentry id="vidioc-subdev-enum-mbus-code">
+  <refmeta>
+    <refentrytitle>ioctl VIDIOC_SUBDEV_ENUM_MBUS_CODE</refentrytitle>
+    &manvol;
+  </refmeta>
+
+  <refnamediv>
+    <refname>VIDIOC_SUBDEV_ENUM_MBUS_CODE</refname>
+    <refpurpose>Enumerate media bus formats</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 v4l2_subdev_mbus_code_enum *
+	<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_SUBDEV_ENUM_MBUS_CODE</para>
+	</listitem>
+      </varlistentry>
+      <varlistentry>
+	<term><parameter>argp</parameter></term>
+	<listitem>
+	  <para></para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Description</title>
+
+    <note>
+      <title>Experimental</title>
+      <para>This is an <link linkend="experimental">experimental</link>
+      interface and may change in the future.</para>
+    </note>
+
+    <para>To enumerate media bus formats available at a given sub-device pad
+    applications initialize the <structfield>pad</structfield> and
+    <structfield>index</structfield> fields of &v4l2-subdev-mbus-code-enum; and
+    call the <constant>VIDIOC_SUBDEV_ENUM_MBUS_CODE</constant> ioctl with a
+    pointer to this structure. Drivers fill the rest of the structure or return
+    an &EINVAL; if either the <structfield>pad</structfield> or
+    <structfield>index</structfield> are invalid. All media bus formats are
+    enumerable by beginning at index zero and incrementing by one until
+    <errorcode>EINVAL</errorcode> is returned.</para>
+
+    <para>Available media bus formats may depend on the current 'try' formats
+    at other pads of the sub-device, as well as on the current active links. See
+    &VIDIOC-SUBDEV-G-FMT; for more information about the try formats.</para>
+
+    <table pgwide="1" frame="none" id="v4l2-subdev-mbus-code-enum">
+      <title>struct <structname>v4l2_subdev_mbus_code_enum</structname></title>
+      <tgroup cols="3">
+	&cs-str;
+	<tbody valign="top">
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>pad</structfield></entry>
+	    <entry>Pad number as reported by the media controller API.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>index</structfield></entry>
+	    <entry>Number of the format in the enumeration, set by the
+	    application.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>code</structfield></entry>
+	    <entry>The media bus format code, as defined in
+	    <xref linkend="v4l2-mbus-format" />.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>reserved</structfield>[9]</entry>
+	    <entry>Reserved for future extensions. Applications and drivers must
+	    set the array to zero.</entry>
+	  </row>
+	</tbody>
+      </tgroup>
+    </table>
+  </refsect1>
+
+  <refsect1>
+    &return-value;
+
+    <variablelist>
+      <varlistentry>
+	<term><errorcode>EINVAL</errorcode></term>
+	<listitem>
+	  <para>The &v4l2-subdev-mbus-code-enum; <structfield>pad</structfield>
+	  references a non-existing pad, or the <structfield>index</structfield>
+	  field is out of bounds.</para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+</refentry>