[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, 154 insertions, 0 deletions

diff --git a/Documentation/DocBook/v4l/vidioc-subdev-enum-frame-size.xml b/Documentation/DocBook/v4l/vidioc-subdev-enum-frame-size.xml
new file mode 100644
index 000000000000..79ce42b7c60c
--- /dev/null
+++ b/Documentation/DocBook/v4l/vidioc-subdev-enum-frame-size.xml
@@ -0,0 +1,154 @@
+<refentry id="vidioc-subdev-enum-frame-size">
+  <refmeta>
+    <refentrytitle>ioctl VIDIOC_SUBDEV_ENUM_FRAME_SIZE</refentrytitle>
+    &manvol;
+  </refmeta>
+
+  <refnamediv>
+    <refname>VIDIOC_SUBDEV_ENUM_FRAME_SIZE</refname>
+    <refpurpose>Enumerate media bus frame sizes</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_frame_size_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_FRAME_SIZE</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>This ioctl allows applications to enumerate all frame sizes
+    supported by a sub-device on the given pad for the given media bus format.
+    Supported formats can be retrieved with the &VIDIOC-SUBDEV-ENUM-MBUS-CODE;
+    ioctl.</para>
+
+    <para>To enumerate frame sizes applications initialize the
+    <structfield>pad</structfield>, <structfield>code</structfield> and
+    <structfield>index</structfield> fields of the
+    &v4l2-subdev-mbus-code-enum; and call the
+    <constant>VIDIOC_SUBDEV_ENUM_FRAME_SIZE</constant> ioctl with a pointer to
+    the structure. Drivers fill the minimum and maximum frame sizes or return
+    an &EINVAL; if one of the input parameters is invalid.</para>
+
+    <para>Sub-devices that only support discrete frame sizes (such as most
+    sensors) will return one or more frame sizes with identical minimum and
+    maximum values.</para>
+
+    <para>Not all possible sizes in given [minimum, maximum] ranges need to be
+    supported. For instance, a scaler that uses a fixed-point scaling ratio
+    might not be able to produce every frame size between the minimum and
+    maximum values. Applications must use the &VIDIOC-SUBDEV-S-FMT; ioctl to
+    try the sub-device for an exact supported frame size.</para>
+
+    <para>Available frame sizes may depend on the current 'try' formats at other
+    pads of the sub-device, as well as on the current active links and the
+    current values of V4L2 controls. See &VIDIOC-SUBDEV-G-FMT; for more
+    information about try formats.</para>
+
+    <table pgwide="1" frame="none" id="v4l2-subdev-frame-size-enum">
+      <title>struct <structname>v4l2_subdev_frame_size_enum</structname></title>
+      <tgroup cols="3">
+	&cs-str;
+	<tbody valign="top">
+	  <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>pad</structfield></entry>
+	    <entry>Pad number as reported by the media controller API.</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>min_width</structfield></entry>
+	    <entry>Minimum frame width, in pixels.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>max_width</structfield></entry>
+	    <entry>Maximum frame width, in pixels.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>min_height</structfield></entry>
+	    <entry>Minimum frame height, in pixels.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>max_height</structfield></entry>
+	    <entry>Maximum frame height, in pixels.</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-frame-size-enum; <structfield>pad</structfield>
+	  references a non-existing pad, the <structfield>code</structfield> is
+	  invalid for the given pad or the <structfield>index</structfield>
+	  field is out of bounds.</para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+</refentry>