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Message-Id: <201208300757.44775.hverkuil@xs4all.nl>
Date: Thu, 30 Aug 2012 07:57:44 -0700
From: Hans Verkuil <hverkuil@...all.nl>
To: Prabhakar Lad <prabhakar.lad@...com>
Cc: LMML <linux-media@...r.kernel.org>,
dlos <davinci-linux-open-source@...ux.davincidsp.com>,
linux-kernel@...r.kernel.org,
Manjunath Hadli <manjunath.hadli@...com>,
Sakari Ailus <sakari.ailus@....fi>,
Hans Verkuil <hans.verkuil@...co.com>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Mauro Carvalho Chehab <mchehab@...radead.org>,
Sylwester Nawrocki <s.nawrocki@...sung.com>,
Hans de Goede <hdegoede@...hat.com>,
Kyungmin Park <kyungmin.park@...sung.com>
Subject: Re: [PATCH v2] media: v4l2-ctrls: add control for dpcm predictor
Hi Prabhakar!
I've got some documentation review comments below...
On Thu August 30 2012 00:58:16 Prabhakar Lad wrote:
> From: Lad, Prabhakar <prabhakar.lad@...com>
>
> add V4L2_CID_DPCM_PREDICTOR control of type menu, which
> determines the dpcm predictor. The predictor can be either
> simple or advanced.
>
> Signed-off-by: Lad, Prabhakar <prabhakar.lad@...com>
> Signed-off-by: Manjunath Hadli <manjunath.hadli@...com>
> Cc: Sakari Ailus <sakari.ailus@....fi>
> Cc: Hans Verkuil <hans.verkuil@...co.com>
> Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Cc: Mauro Carvalho Chehab <mchehab@...radead.org>
> Cc: Sylwester Nawrocki <s.nawrocki@...sung.com>
> Cc: Hans de Goede <hdegoede@...hat.com>
> Cc: Kyungmin Park <kyungmin.park@...sung.com>
> ---
> This patches has one checkpatch warning for line over
> 80 characters altough it can be avoided I have kept it
> for consistency.
>
> Changes for v2:
> 1: Added documentaion in controls.xml pointed by Sylwester.
> 2: Chnaged V4L2_DPCM_PREDICTOR_ADVANCE to V4L2_DPCM_PREDICTOR_ADVANCED
> pointed by Sakari.
>
> Documentation/DocBook/media/v4l/controls.xml | 25 ++++++++++++++++++++++++-
> drivers/media/v4l2-core/v4l2-ctrls.c | 9 +++++++++
> include/linux/videodev2.h | 5 +++++
> 3 files changed, 38 insertions(+), 1 deletions(-)
>
> diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml
> index 93b9c68..84746d0 100644
> --- a/Documentation/DocBook/media/v4l/controls.xml
> +++ b/Documentation/DocBook/media/v4l/controls.xml
> @@ -4267,7 +4267,30 @@ interface and may change in the future.</para>
> pixels / second.
> </entry>
> </row>
> - <row><entry></entry></row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_DPCM_PREDICTOR</constant></entry>
> + <entry>menu</entry>
> + </row>
> + <row id="v4l2-dpcm-predictor">
> + <entry spanname="descr"> DPCM Predictor: depicts what type of prediction
> + is used simple or advanced.
This is not useful information. It basically just rephrases the name of the
define without actually telling me anything.
I would expect to see here at least the following:
- what the DPCM abbreviation stands for
- a link or bibliography reference to the relevant standard (if there is any)
- a high-level explanation of what this do and what the difference is between
simple and advanced.
If this is part of a video compression standard, then this control would probably
belong to the MPEG control class as well.
Regards,
Hans
> + </entry>
> + </row>
> + <row>
> + <entrytbl spanname="descr" cols="2">
> + <tbody valign="top">
> + <row>
> + <entry><constant>V4L2_DPCM_PREDICTOR_SIMPLE</constant></entry>
> + <entry>Predictor type is simple</entry>
> + </row>
> + <row>
> + <entry><constant>V4L2_DPCM_PREDICTOR_ADVANCED</constant></entry>
> + <entry>Predictor type is advanced</entry>
> + </row>
> + </tbody>
> + </entrytbl>
> + </row>
> + <row><entry></entry></row>
> </tbody>
> </tgroup>
> </table>
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index b6a2ee7..2d7bc15 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -425,6 +425,11 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
> "Gray",
> NULL,
> };
> + static const char * const dpcm_predictor[] = {
> + "Simple Predictor",
> + "Advanced Predictor",
> + NULL,
> + };
>
> switch (id) {
> case V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ:
> @@ -502,6 +507,8 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
> return mpeg4_profile;
> case V4L2_CID_JPEG_CHROMA_SUBSAMPLING:
> return jpeg_chroma_subsampling;
> + case V4L2_CID_DPCM_PREDICTOR:
> + return dpcm_predictor;
>
> default:
> return NULL;
> @@ -732,6 +739,7 @@ const char *v4l2_ctrl_get_name(u32 id)
> case V4L2_CID_IMAGE_PROC_CLASS: return "Image Processing Controls";
> case V4L2_CID_LINK_FREQ: return "Link Frequency";
> case V4L2_CID_PIXEL_RATE: return "Pixel Rate";
> + case V4L2_CID_DPCM_PREDICTOR: return "DPCM Predictor";
>
> default:
> return NULL;
> @@ -832,6 +840,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
> case V4L2_CID_ISO_SENSITIVITY_AUTO:
> case V4L2_CID_EXPOSURE_METERING:
> case V4L2_CID_SCENE_MODE:
> + case V4L2_CID_DPCM_PREDICTOR:
> *type = V4L2_CTRL_TYPE_MENU;
> break;
> case V4L2_CID_LINK_FREQ:
> diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
> index 6d6dfa7..ca9fb78 100644
> --- a/include/linux/videodev2.h
> +++ b/include/linux/videodev2.h
> @@ -2000,6 +2000,11 @@ enum v4l2_jpeg_chroma_subsampling {
>
> #define V4L2_CID_LINK_FREQ (V4L2_CID_IMAGE_PROC_CLASS_BASE + 1)
> #define V4L2_CID_PIXEL_RATE (V4L2_CID_IMAGE_PROC_CLASS_BASE + 2)
> +#define V4L2_CID_DPCM_PREDICTOR (V4L2_CID_IMAGE_PROC_CLASS_BASE + 3)
> +enum v4l2_dpcm_predictor {
> + V4L2_DPCM_PREDICTOR_SIMPLE = 0,
> + V4L2_DPCM_PREDICTOR_ADVANCED = 1,
> +};
>
> /*
> * T U N I N G
>
--
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