3 files changed, 189 insertions, 0 deletions

diff --git a/Documentation/DocBook/v4l/dev-subdev.xml b/Documentation/DocBook/v4l/dev-subdev.xml
index fc62e65f45ef..e9eb8af0f303 100644
--- a/Documentation/DocBook/v4l/dev-subdev.xml
+++ b/Documentation/DocBook/v4l/dev-subdev.xml
@@ -275,6 +275,39 @@
       </para>
     </section>
 
+    <section>
+      <title>Cropping and scaling</title>
+
+      <para>Many sub-devices support cropping frames on their input or output
+      pads (or possible even on both). Cropping is used to select the area of
+      interest in an image, typically on a video sensor or video decoder. It can
+      also be used as part of digital zoom implementations to select the area of
+      the image that will be scaled up.</para>
+
+      <para>Crop settings are defined by a crop rectangle and represented in a
+      &v4l2-rect; by the coordinates of the top left corner and the rectangle
+      size. Both the coordinates and sizes are expressed in pixels.</para>
+
+      <para>The crop rectangle is retrieved and set using the
+      &VIDIOC-SUBDEV-G-CROP; and &VIDIOC-SUBDEV-S-CROP; ioctls. Like for pad
+      formats, drivers store try and active crop rectangles. The format
+      negotiation mechanism applies to crop settings as well.</para>
+
+      <para>On input pads, cropping is applied relatively to the current pad
+      format. The pad format represents the image size as received by the
+      sub-device from the previous block in the pipeline, and the crop rectangle
+      represents the sub-image that will be transmitted further inside the
+      sub-device for processing. The crop rectangle be entirely containted
+      inside the input image size.</para>
+
+      <para>Input crop rectangle are reset to their default value when the input
+      image format is modified. Drivers should use the input image size as the
+      crop rectangle default value, but hardware requirements may prevent this.
+      </para>
+
+      <para>Cropping behaviour on output pads is not defined.</para>
+
+    </section>
   </section>
 
   &sub-subdev-formats;
diff --git a/Documentation/DocBook/v4l/v4l2.xml b/Documentation/DocBook/v4l/v4l2.xml
index a436716ef3bc..3a6e3b5c0944 100644
--- a/Documentation/DocBook/v4l/v4l2.xml
+++ b/Documentation/DocBook/v4l/v4l2.xml
@@ -510,6 +510,7 @@ and discussions on the V4L mailing list.</revremark>
     &sub-subdev-enum-frame-interval;
     &sub-subdev-enum-frame-size;
     &sub-subdev-enum-mbus-code;
+    &sub-subdev-g-crop;
     &sub-subdev-g-fmt;
     &sub-subdev-g-frame-interval;
     &sub-subscribe-event;
diff --git a/Documentation/DocBook/v4l/vidioc-subdev-g-crop.xml b/Documentation/DocBook/v4l/vidioc-subdev-g-crop.xml
new file mode 100644
index 000000000000..06197323a8cc
--- /dev/null
+++ b/Documentation/DocBook/v4l/vidioc-subdev-g-crop.xml
@@ -0,0 +1,155 @@
+<refentry id="vidioc-subdev-g-crop">
+  <refmeta>
+    <refentrytitle>ioctl VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP</refentrytitle>
+    &manvol;
+  </refmeta>
+
+  <refnamediv>
+    <refname>VIDIOC_SUBDEV_G_CROP</refname>
+    <refname>VIDIOC_SUBDEV_S_CROP</refname>
+    <refpurpose>Get or set the crop rectangle on a subdev pad</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_crop *<parameter>argp</parameter></paramdef>
+      </funcprototype>
+    </funcsynopsis>
+    <funcsynopsis>
+      <funcprototype>
+        <funcdef>int <function>ioctl</function></funcdef>
+        <paramdef>int <parameter>fd</parameter></paramdef>
+        <paramdef>int <parameter>request</parameter></paramdef>
+        <paramdef>const struct v4l2_subdev_crop *<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_G_CROP, VIDIOC_SUBDEV_S_CROP</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 retrieve the current crop rectangle applications set the
+    <structfield>pad</structfield> field of a &v4l2-subdev-crop; to the
+    desired pad number as reported by the media API and the
+    <structfield>which</structfield> field to
+    <constant>V4L2_SUBDEV_FORMAT_ACTIVE</constant>. They then call the
+    <constant>VIDIOC_SUBDEV_G_CROP</constant> ioctl with a pointer to this
+    structure. The driver fills the members of the <structfield>rect</structfield>
+    field or returns &EINVAL; if the input arguments are invalid, or if cropping
+    is not supported on the given pad.</para>
+
+    <para>To change the current crop rectangle applications set both the
+    <structfield>pad</structfield> and <structfield>which</structfield> fields
+    and all members of the <structfield>rect</structfield> field. They then call
+    the <constant>VIDIOC_SUBDEV_S_CROP</constant> ioctl with a pointer to this
+    structure. The driver verifies the requested crop rectangle, adjusts it
+    based on the hardware capabilities and configures the device. Upon return
+    the &v4l2-subdev-crop; contains the current format as would be returned
+    by a <constant>VIDIOC_SUBDEV_G_CROP</constant> call.</para>
+
+    <para>Applications can query the device capabilities by setting the
+    <structfield>which</structfield> to
+    <constant>V4L2_SUBDEV_FORMAT_TRY</constant>. When set, 'try' crop
+    rectangles are not applied to the device by the driver, but are mangled
+    exactly as active crop rectangles and stored in the sub-device file handle.
+    Two applications querying the same sub-device would thus not interact with
+    each other.</para>
+
+    <para>Drivers must not return an error solely because the requested crop
+    rectangle doesn't match the device capabilities. They must instead modify
+    the rectangle to match what the hardware can provide. The modified format
+    should be as close as possible to the original request.</para>
+
+    <table pgwide="1" frame="none" id="v4l2-subdev-crop">
+      <title>struct <structname>v4l2_subdev_crop</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 framework.</entry>
+          </row>
+          <row>
+            <entry>__u32</entry>
+            <entry><structfield>which</structfield></entry>
+            <entry>Crop rectangle to get or set, from
+            &v4l2-subdev-format-whence;.</entry>
+          </row>
+          <row>
+            <entry>&v4l2-rect;</entry>
+            <entry><structfield>rect</structfield></entry>
+            <entry>Crop rectangle boundaries, in pixels.</entry>
+          </row>
+          <row>
+            <entry>__u32</entry>
+            <entry><structfield>reserved</structfield>[8]</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>EBUSY</errorcode></term>
+        <listitem>
+          <para>The crop rectangle can't be changed because the pad is currently
+          busy. This can be caused, for instance, by an active video stream on
+          the pad. The ioctl must not be retried without performing another
+          action to fix the problem first. Only returned by
+          <constant>VIDIOC_SUBDEV_S_CROP</constant></para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><errorcode>EINVAL</errorcode></term>
+        <listitem>
+          <para>The &v4l2-subdev-crop; <structfield>pad</structfield>
+          references a non-existing pad, the <structfield>which</structfield>
+          field references a non-existing format, or cropping is not supported
+          on the given subdev pad.</para>
+        </listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+</refentry>