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Date: Fri, 27 May 2016 14:38:41 +0200
From: Hans Verkuil <hverkuil@...all.nl>
To: Nick Dyer <nick.dyer@...ev.co.uk>,
Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-media@...r.kernel.org,
Benjamin Tissoires <benjamin.tissoires@...hat.com>,
Benson Leung <bleung@...omium.org>,
Alan Bowens <Alan.Bowens@...el.com>,
Javier Martinez Canillas <javier@....samsung.com>,
Chris Healy <cphealy@...il.com>,
Henrik Rydberg <rydberg@...math.org>,
Andrew Duggan <aduggan@...aptics.com>,
James Chen <james.chen@....com.tw>,
Dudley Du <dudl@...ress.com>,
Andrew de los Reyes <adlr@...omium.org>,
sheckylin@...omium.org, Peter Hutterer <peter.hutterer@...-t.net>,
Florian Echtler <floe@...terbrot.org>, mchehab@....samsung.com
Subject: Re: [PATCH v2 2/8] [media] Add signed 16-bit pixel format
On 05/04/2016 07:07 PM, Nick Dyer wrote:
> This will be used for output of raw touch data.
>
> Signed-off-by: Nick Dyer <nick.dyer@...ev.co.uk>
> ---
> Documentation/DocBook/media/v4l/pixfmt-ys16.xml | 79 +++++++++++++++++++++++++
> Documentation/DocBook/media/v4l/pixfmt.xml | 1 +
> drivers/media/v4l2-core/v4l2-ioctl.c | 1 +
> include/uapi/linux/videodev2.h | 1 +
> 4 files changed, 82 insertions(+)
> create mode 100644 Documentation/DocBook/media/v4l/pixfmt-ys16.xml
>
> diff --git a/Documentation/DocBook/media/v4l/pixfmt-ys16.xml b/Documentation/DocBook/media/v4l/pixfmt-ys16.xml
> new file mode 100644
> index 0000000..f92d65e
> --- /dev/null
> +++ b/Documentation/DocBook/media/v4l/pixfmt-ys16.xml
> @@ -0,0 +1,79 @@
> +<refentry id="V4L2-PIX-FMT-YS16">
> + <refmeta>
> + <refentrytitle>V4L2_PIX_FMT_YS16 ('YS16')</refentrytitle>
> + &manvol;
> + </refmeta>
> + <refnamediv>
> + <refname><constant>V4L2_PIX_FMT_YS16</constant></refname>
> + <refpurpose>Grey-scale image</refpurpose>
> + </refnamediv>
> + <refsect1>
> + <title>Description</title>
> +
> + <para>This is a signed grey-scale image with a depth of 16 bits per
> +pixel. The most significant byte is stored at higher memory addresses
> +(little-endian).</para>
I'm not sure this should be described in terms of grey-scale, since negative
values make no sense for that. How are these values supposed to be interpreted
if you want to display them? -32768 == black and 32767 is white?
Regards,
Hans
> +
> + <example>
> + <title><constant>V4L2_PIX_FMT_YS16</constant> 4 × 4
> +pixel image</title>
> +
> + <formalpara>
> + <title>Byte Order.</title>
> + <para>Each cell is one byte.
> + <informaltable frame="none">
> + <tgroup cols="9" align="center">
> + <colspec align="left" colwidth="2*" />
> + <tbody valign="top">
> + <row>
> + <entry>start + 0:</entry>
> + <entry>Y'<subscript>00low</subscript></entry>
> + <entry>Y'<subscript>00high</subscript></entry>
> + <entry>Y'<subscript>01low</subscript></entry>
> + <entry>Y'<subscript>01high</subscript></entry>
> + <entry>Y'<subscript>02low</subscript></entry>
> + <entry>Y'<subscript>02high</subscript></entry>
> + <entry>Y'<subscript>03low</subscript></entry>
> + <entry>Y'<subscript>03high</subscript></entry>
> + </row>
> + <row>
> + <entry>start + 8:</entry>
> + <entry>Y'<subscript>10low</subscript></entry>
> + <entry>Y'<subscript>10high</subscript></entry>
> + <entry>Y'<subscript>11low</subscript></entry>
> + <entry>Y'<subscript>11high</subscript></entry>
> + <entry>Y'<subscript>12low</subscript></entry>
> + <entry>Y'<subscript>12high</subscript></entry>
> + <entry>Y'<subscript>13low</subscript></entry>
> + <entry>Y'<subscript>13high</subscript></entry>
> + </row>
> + <row>
> + <entry>start + 16:</entry>
> + <entry>Y'<subscript>20low</subscript></entry>
> + <entry>Y'<subscript>20high</subscript></entry>
> + <entry>Y'<subscript>21low</subscript></entry>
> + <entry>Y'<subscript>21high</subscript></entry>
> + <entry>Y'<subscript>22low</subscript></entry>
> + <entry>Y'<subscript>22high</subscript></entry>
> + <entry>Y'<subscript>23low</subscript></entry>
> + <entry>Y'<subscript>23high</subscript></entry>
> + </row>
> + <row>
> + <entry>start + 24:</entry>
> + <entry>Y'<subscript>30low</subscript></entry>
> + <entry>Y'<subscript>30high</subscript></entry>
> + <entry>Y'<subscript>31low</subscript></entry>
> + <entry>Y'<subscript>31high</subscript></entry>
> + <entry>Y'<subscript>32low</subscript></entry>
> + <entry>Y'<subscript>32high</subscript></entry>
> + <entry>Y'<subscript>33low</subscript></entry>
> + <entry>Y'<subscript>33high</subscript></entry>
> + </row>
> + </tbody>
> + </tgroup>
> + </informaltable>
> + </para>
> + </formalpara>
> + </example>
> + </refsect1>
> +</refentry>
> diff --git a/Documentation/DocBook/media/v4l/pixfmt.xml b/Documentation/DocBook/media/v4l/pixfmt.xml
> index d871245..6f7aa0e 100644
> --- a/Documentation/DocBook/media/v4l/pixfmt.xml
> +++ b/Documentation/DocBook/media/v4l/pixfmt.xml
> @@ -1619,6 +1619,7 @@ information.</para>
> &sub-y12;
> &sub-y10b;
> &sub-y16;
> + &sub-ys16;
> &sub-y16-be;
> &sub-uv8;
> &sub-yuyv;
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 8a018c6..c7dabaa 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -1154,6 +1154,7 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
> case V4L2_PIX_FMT_Y10: descr = "10-bit Greyscale"; break;
> case V4L2_PIX_FMT_Y12: descr = "12-bit Greyscale"; break;
> case V4L2_PIX_FMT_Y16: descr = "16-bit Greyscale"; break;
> + case V4L2_PIX_FMT_YS16: descr = "16-bit Greyscale (Signed)"; break;
> case V4L2_PIX_FMT_Y16_BE: descr = "16-bit Greyscale BE"; break;
> case V4L2_PIX_FMT_Y10BPACK: descr = "10-bit Greyscale (Packed)"; break;
> case V4L2_PIX_FMT_PAL8: descr = "8-bit Palette"; break;
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 14cd5eb..ab577dd 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -496,6 +496,7 @@ struct v4l2_pix_format {
> #define V4L2_PIX_FMT_Y12 v4l2_fourcc('Y', '1', '2', ' ') /* 12 Greyscale */
> #define V4L2_PIX_FMT_Y16 v4l2_fourcc('Y', '1', '6', ' ') /* 16 Greyscale */
> #define V4L2_PIX_FMT_Y16_BE v4l2_fourcc_be('Y', '1', '6', ' ') /* 16 Greyscale BE */
> +#define V4L2_PIX_FMT_YS16 v4l2_fourcc('Y', 'S', '1', '6') /* signed 16-bit Greyscale */
>
> /* Grey bit-packed formats */
> #define V4L2_PIX_FMT_Y10BPACK v4l2_fourcc('Y', '1', '0', 'B') /* 10 Greyscale bit-packed */
>
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