Hi Sakari, Thanks for the patch. On Tuesday 20 December 2011 21:27:58 Sakari Ailus wrote: [snip] > diff --git a/Documentation/DocBook/media/v4l/dev-subdev.xml > b/Documentation/DocBook/media/v4l/dev-subdev.xml index 0916a73..722db60 > 100644 > --- a/Documentation/DocBook/media/v4l/dev-subdev.xml > +++ b/Documentation/DocBook/media/v4l/dev-subdev.xml [snip] > @@ -288,26 +288,81 @@ [snip] > + <para>Scaling operation changes the size of the image by scaling > + it to new dimensions. Some sub-devices support it. The scaled > + size (width and height) is represented by &v4l2-rect;. In the > + case of scaling, top and left will always be zero. Scaling is > + configured using &sub-subdev-g-selection; and > + <constant>V4L2_SUBDEV_SEL_COMPOSE_ACTIVE</constant> selection > + target on the sink pad of the subdev. The scaling is performed > + related to the width and height of the crop rectangle on the > + subdev's sink pad.</para> > + > + <para>As for pad formats, drivers store try and active > + rectangles for the selection targets of ACTIVE type <xref > + linkend="v4l2-subdev-selection-targets">.</xref></para> > + > + <para>On sink 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.</para> > + > + <para>On source pads, cropping is similar to sink pads, with the > + exception that the source size from which the cropping is > + performed, is the COMPOSE rectangle on the sink pad. In both > + sink and source pads, the crop rectangle must be entirely > + containted inside the source image size for the crop > + operation.</para> > + > + <para>The drivers should always use the closest possible > + rectangle the user requests on all selection targets, unless > + specificly told otherwise<xref > + linkend="v4l2-subdev-selection-flags">.</xref></para> > + </section> This sounds a bit confusing to me. One issue is that composing is not formally defined. I think it would help if you could draw a diagram that shows how the operations are applied, and modify the text to describe the diagram, using the natural order of the compose and crop operations on sink and source pads. > + <section> > + <title>Order of configuration and format propagation</title> > + > + <para>The order of image processing steps will always be from > + the sink pad towards the source pad. This is also reflected in > + the order in which the configuration must be performed by the > + user. The format is propagated within the subdev along the later > + processing steps. For example, setting the sink pad format > + causes all the selection rectangles and the source pad format to > + be set to sink pad format --- if allowed by the hardware, and if > + not, then closest possible. The coordinates to a step always > + refer to the active size of the previous step.</para> This also sounds a bit ambiguous if I try to ignore the fact that I know how it works :-) You should at least make it explicit that propagation inside subdevs is performed by the driver(s), and that propagation outside subdevs is to be handled by userspace. > + <orderedlist> > + <listitem>Sink pad format. The user configures the sink pad > + format. This format defines the parameters of the image the > + entity receives through the pad for further processing.</listitem> > > - <para>Cropping behaviour on output pads is not defined.</para> > + <listitem>Sink pad active crop selection. The sink pad crop > + defines the performed to the sink pad format.</listitem> > > + <listitem>Sink pad active compose selection. The sink pad compose > + rectangle defines the scaling ratio compared to the size of > + the sink pad crop rectangle.</listitem> > + > + <listitem>Source pad active crop selection. Crop on the source > + pad defines crop performed to the image scaled according to > + the sink pad compose rectangle.</listitem> > + > + <listitem>Source pad active compose selection. The source pad > + compose defines the size and location of the compose > + rectangle.</listitem> > + > + <listitem>Source pad format. The source pad format defines the > + output pixel format of the subdev, as well as the other > + parameters with the exception of the image width and > + height.</listitem> > + > + </orderedlist> > </section> > + > </section> > > &sub-subdev-formats; [snip] > diff --git a/Documentation/DocBook/media/v4l/vidioc-subdev-g-selection.xml > b/Documentation/DocBook/media/v4l/vidioc-subdev-g-selection.xml new file > mode 100644 > index 0000000..5fbcd65 > --- /dev/null > +++ b/Documentation/DocBook/media/v4l/vidioc-subdev-g-selection.xml > @@ -0,0 +1,226 @@ [snip] > + <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>The selections are used to configure various image > + processing functionality performed by the subdevs which affect the > + image size. This currently includes cropping, scaling and > + composition.</para> > + > + <para>The selections replace the crop API &sub-subdev-g-crop;. All > + the function of the crop API, and more, are supported by the > + selections API.</para> > + > + <para>See <xref linkend="subdev">Sub-device interface</xref> for > + more information on how each selection target affects the image > + processing pipeline inside the subdevice.</para> > + > + <section> > + <title>Types of selection targets</title> > + > + <para>The are four types of selection targets: active, default, > + bounds and padding. The ACTIVE targets are the targets which > + configure the hardware. The DEFAULT target provides the default > + for the ACTIVE selection. The BOUNDS target will return the > + maximum width and height of the target. What about the minimum ? > The PADDED target > + provides the width and height for the padded image, Is it valid for both crop and compose rectangles ? > and is > + directly affected by the ACTIVE target. The PADDED targets may > + be configurable depending on the hardware.</para> If that's configurable drivers will need a way to store it in the file handle. > + </section> > + > + <table pgwide="1" frame="none" id="v4l2-subdev-selection-targets"> > + <title>V4L2 subdev selection targets</title> > + <tgroup cols="3"> > + &cs-def; > + <tbody valign="top"> > + <row> > + <entry><constant>V4L2_SUBDEV_SEL_TGT_CROP_ACTIVE</constant></entry> > + <entry>0</entry> > + <entry>Active crop. Defines the cropping > + performed by the processing step.</entry> > + </row> > + <row> > + <entry><constant>V4L2_SUBDEV_SEL_TGT_CROP_DEFAULT</constant></entry> > + <entry>1</entry> > + <entry>Default crop rectangle.</entry> > + </row> > + <row> > + <entry><constant>V4L2_SUBDEV_SEL_TGT_CROP_BOUNDS</constant></entry> > + <entry>2</entry> > + <entry>Bounds of the crop rectangle.</entry> > + </row> > + <row> > + > <entry><constant>V4L2_SUBDEV_SEL_TGT_COMPOSE_ACTIVE</constant></entry> + > <entry>256</entry> > + <entry>Active compose rectangle. Used to configure scaling > + on sink pads and composition on source pads.</entry> > + </row> > + <row> > + > <entry><constant>V4L2_SUBDEV_SEL_TGT_COMPOSE_DEFAULT</constant></entry> + > <entry>257</entry> > + <entry>Default compose rectangle.</entry> > + </row> > + <row> > + > <entry><constant>V4L2_SUBDEV_SEL_TGT_COMPOSE_BOUNDS</constant></entry> + > <entry>258</entry> > + <entry>Bounds of the compose rectangle.</entry> > + </row> > + </tbody> > + </tgroup> > + </table> > + > + <table pgwide="1" frame="none" id="v4l2-subdev-selection-flags"> > + <title>V4L2 subdev selection flags</title> > + <tgroup cols="3"> > + &cs-def; > + <tbody valign="top"> > + <row> > + <entry><constant>V4L2_SUBDEV_SEL_FLAG_SIZE_GE</constant></entry> > + <entry>(1 << 0)</entry> > + <entry>Suggest the driver it should choose greater or > + equal rectangle (in size) than was requested.</entry> > + </row> > + <row> > + <entry><constant>V4L2_SUBDEV_SEL_FLAG_SIZE_LE</constant></entry> > + <entry>(1 << 1)</entry> > + <entry>Suggest the driver it should choose lesser or > + equal rectangle (in size) than was requested.</entry> > + </row> > + <row> > + <entry><constant>V4L2_SUBDEV_SEL_FLAG_KEEP_CONFIG</constant></entry> > + <entry>(1 << 2)</entry> > + <entry>The configuration should not be propagated to any > + further processing steps. If this flag is not given, the > + configuration is propagated inside the subdevice to all > + further processing steps.</entry> > + </row> > + </tbody> > + </tgroup> > + </table> > + > + <table pgwide="1" frame="none" id="v4l2-subdev-selection"> > + <title>struct <structname>v4l2_subdev_selection</structname></title> > + <tgroup cols="3"> > + &cs-str; > + <tbody valign="top"> > + <row> > + <entry>__u32</entry> > + <entry><structfield>which</structfield></entry> > + <entry>Active or try selection, from > + &v4l2-subdev-format-whence;.</entry> > + </row> > + <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>target</structfield></entry> > + <entry>Target selection rectangle. See > + <xref linkend="v4l2-subdev-selection-targets">.</xref>.</entry> > + </row> > + <row> > + <entry>__u32</entry> > + <entry><structfield>flags</structfield></entry> > + <entry>Flags. See > + <xref linkend="v4l2-subdev-selection-flags">.</xref></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 selection 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_SELECTION</constant></para> > + </listitem> > + </varlistentry> > + <varlistentry> > + <term><errorcode>EINVAL</errorcode></term> > + <listitem> > + <para>The &v4l2-subdev-selection; > + <structfield>pad</structfield> references a non-existing > + pad, the <structfield>which</structfield> field references a > + non-existing format, or the selection target is not > + supported on the given subdev pad.</para> > + </listitem> > + </varlistentry> > + </variablelist> > + </refsect1> > +</refentry> -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
