Re: [PATCH v2 04/23] v4l: Add premultiplied alpha flag for pixel formats

[Hans Verkuil <hverkuil@xs4all.nl>]

Hi Laurent,

A small comment below:

On 06/24/2014 01:54 AM, Laurent Pinchart wrote:
> When set, the new V4L2_PIX_FMT_FLAG_PREMUL_ALPHA flag indicates that the
> pixel values are premultiplied by the alpha channel value.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> ---
>   Documentation/DocBook/media/v4l/pixfmt.xml | 28 +++++++++++++++++++++++++++-
>   Documentation/DocBook/media/v4l/v4l2.xml   |  2 +-
>   drivers/media/v4l2-core/v4l2-ioctl.c       |  5 +++--
>   include/uapi/linux/videodev2.h             |  8 +++++++-
>   4 files changed, 38 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/DocBook/media/v4l/pixfmt.xml b/Documentation/DocBook/media/v4l/pixfmt.xml
> index 8c56cacd..c8e1487 100644
> --- a/Documentation/DocBook/media/v4l/pixfmt.xml
> +++ b/Documentation/DocBook/media/v4l/pixfmt.xml
> @@ -135,6 +135,12 @@ extended fields were set to zero. On return drivers must set the
>   <constant>V4L2_PIX_FMT_PRIV_MAGIC</constant> and all the extended field to
>   applicable values.</para></entry>
>   	</row>
> +	<row>
> +	  <entry>__u32</entry>
> +	  <entry><structfield>flags</structfield></entry>
> +	    <entry>Flags set by the application or driver, see <xref
> +linkend="format-flags" />.</entry>
> +	</row>
>         </tbody>
>       </tgroup>
>     </table>
> @@ -220,9 +226,15 @@ codes can be used.</entry>
>             and the number of valid entries in the
>             <structfield>plane_fmt</structfield> array.</entry>
>           </row>
> +	<row>
> +	  <entry>__u8</entry>
> +	  <entry><structfield>flags</structfield></entry>
> +	  <entry>Flags set by the application or driver, see <xref
> +linkend="format-flags" />.</entry>
> +	</row>
>           <row>
>             <entry>__u8</entry>
> -          <entry><structfield>reserved[11]</structfield></entry>
> +          <entry><structfield>reserved[10]</structfield></entry>
>             <entry>Reserved for future extensions. Should be zeroed by the
>              application.</entry>
>           </row>
> @@ -1079,4 +1091,18 @@ concatenated to form the JPEG stream. </para>
>   	</tbody>
>         </tgroup>
>       </table>
> +
> +    <table frame="none" pgwide="1" id="format-flags">
> +      <title>Format Flags</title>
> +      <tgroup cols="3">
> +	&cs-def;
> +	<tbody valign="top">
> +	  <row>
> +	    <entry><constant>V4L2_PIX_FMT_FLAG_PREMUL_ALPHA</constant></entry>
> +	    <entry>0x00000001</entry>
> +	    <entry>The pixel values are premultiplied by the alpha channel value.</entry>

It would be helpful if you would give a small example here.

Regards,

	Hans

> +	  </row>
> +	</tbody>
> +      </tgroup>
> +    </table>
>     </section>
> diff --git a/Documentation/DocBook/media/v4l/v4l2.xml b/Documentation/DocBook/media/v4l/v4l2.xml
> index d0a48be..f2f81f0 100644
> --- a/Documentation/DocBook/media/v4l/v4l2.xml
> +++ b/Documentation/DocBook/media/v4l/v4l2.xml
> @@ -155,7 +155,7 @@ applications. -->
>   	<revnumber>3.16</revnumber>
>   	<date>2014-05-27</date>
>   	<authorinitials>lp</authorinitials>
> -	<revremark>Extended &v4l2-pix-format;.
> +	<revremark>Extended &v4l2-pix-format;. Added format flags.
>   	</revremark>
>         </revision>
>
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 01b4588..5a25159 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -256,7 +256,8 @@ static void v4l_print_format(const void *arg, bool write_only)
>   		pix = &p->fmt.pix;
>   		pr_cont(", width=%u, height=%u, "
>   			"pixelformat=%c%c%c%c, field=%s, "
> -			"bytesperline=%u, sizeimage=%u, colorspace=%d\n",
> +			"bytesperline=%u, sizeimage=%u, colorspace=%d, "
> +			"flags %u\n",
>   			pix->width, pix->height,
>   			(pix->pixelformat & 0xff),
>   			(pix->pixelformat >>  8) & 0xff,
> @@ -264,7 +265,7 @@ static void v4l_print_format(const void *arg, bool write_only)
>   			(pix->pixelformat >> 24) & 0xff,
>   			prt_names(pix->field, v4l2_field_names),
>   			pix->bytesperline, pix->sizeimage,
> -			pix->colorspace);
> +			pix->colorspace, pix->flags);
>   		break;
>   	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
>   	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 2656a94..7861b50 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -288,6 +288,7 @@ struct v4l2_pix_format {
>   	__u32          		sizeimage;
>   	__u32			colorspace;	/* enum v4l2_colorspace */
>   	__u32			priv;		/* private data, depends on pixelformat */
> +	__u32			flags;		/* format flags (V4L2_PIX_FMT_FLAG_*) */
>   };
>
>   /*      Pixel format         FOURCC                          depth  Description  */
> @@ -452,6 +453,9 @@ struct v4l2_pix_format {
>   /* priv field value to indicates that subsequent fields are valid. */
>   #define V4L2_PIX_FMT_PRIV_MAGIC		0xdeadbeef
>
> +/* Flags */
> +#define V4L2_PIX_FMT_FLAG_PREMUL_ALPHA	0x00000001
> +
>   /*
>    *	F O R M A T   E N U M E R A T I O N
>    */
> @@ -1726,6 +1730,7 @@ struct v4l2_plane_pix_format {
>    * @colorspace:		enum v4l2_colorspace; supplemental to pixelformat
>    * @plane_fmt:		per-plane information
>    * @num_planes:		number of planes for this format
> + * @flags:		format flags (V4L2_PIX_FMT_FLAG_*)
>    */
>   struct v4l2_pix_format_mplane {
>   	__u32				width;
> @@ -1736,7 +1741,8 @@ struct v4l2_pix_format_mplane {
>
>   	struct v4l2_plane_pix_format	plane_fmt[VIDEO_MAX_PLANES];
>   	__u8				num_planes;
> -	__u8				reserved[11];
> +	__u8				flags;
> +	__u8				reserved[10];
>   } __attribute__ ((packed));
>
>   /**
>