linux-kernel - Re: [PATCH v2] drm/color: Document CTM eqations

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Message-ID: <20170131120236.GA24500@e106950-lin.cambridge.arm.com>
Date:   Tue, 31 Jan 2017 12:02:37 +0000
From:   Brian Starkey <brian.starkey@....com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Sean Paul <seanpaul@...omium.org>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Lionel Landwerlin <lionel.g.landwerlin@...el.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>
Subject: Re: [PATCH v2] drm/color: Document CTM eqations

Hi Jani,

On Tue, Jan 31, 2017 at 01:30:41PM +0200, Jani Nikula wrote:
>On Tue, 31 Jan 2017, Brian Starkey <brian.starkey@....com> wrote:
>> Explicitly state the expected CTM equations in the kerneldoc for the CTM
>> property, and the form of the matrix on struct drm_color_ctm.
>>
>> Cc: Ville Syrjälä <ville.syrjala@...ux.intel.com>
>> Cc: Lionel Landwerlin <lionel.g.landwerlin@...el.com>
>> Cc: Daniel Vetter <daniel.vetter@...ll.ch>
>> Signed-off-by: Brian Starkey <brian.starkey@....com>
>> ---
>>  drivers/gpu/drm/drm_color_mgmt.c |   13 +++++++++++++
>>  include/uapi/drm/drm_mode.h      |    8 +++++++-
>>  2 files changed, 20 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c
>> index 789b4c65cd69..7573ca4b6ea6 100644
>> --- a/drivers/gpu/drm/drm_color_mgmt.c
>> +++ b/drivers/gpu/drm/drm_color_mgmt.c
>> @@ -62,6 +62,19 @@
>>   *	unit/pass-thru matrix should be used. This is generally the driver
>>   *	boot-up state too.
>>   *
>> + *	The output vector is related to the input vector as below:
>> + *
>> + *	| ``out[0] = matrix[0] * in[0] + matrix[1] * in[1] + matrix[2] * in[2];``
>> + *	| ``out[1] = matrix[3] * in[0] + matrix[4] * in[1] + matrix[5] * in[2];``
>> + *	| ``out[2] = matrix[6] * in[0] + matrix[7] * in[1] + matrix[8] * in[2];``
>
>Would that not work better with a preformatted block? Replace the colon
>in the preceding paragraph with the double colon ::, and indent the
>block.
>

Ah thanks for the tip, I couldn't get it to work but it looks like my
syntax was a bit off. I'll resend with that change.

>> + *
>> + *	The component order in the input/output vectors is assumed to be
>> + *	{ R, G, B }.
>> + *
>> + *	The color-space of the input vector must not be confused with the
>> + *	color-space implied by a framebuffer pixel format, which may be the same
>> + *	or different.
>> + *
>>   * “GAMMA_LUT”:
>>   *	Blob property to set the gamma lookup table (LUT) mapping pixel data
>>   *	after the transformation matrix to data sent to the connector. The
>> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
>> index ce7efe2e8a5e..3401637caf8e 100644
>> --- a/include/uapi/drm/drm_mode.h
>> +++ b/include/uapi/drm/drm_mode.h
>> @@ -525,7 +525,13 @@ struct drm_mode_crtc_lut {
>>  };
>>
>>  struct drm_color_ctm {
>> -	/* Conversion matrix in S31.32 format. */
>> +	/*
>> +	 * Conversion matrix in S31.32 format, in row-major form:
>> +	 *
>> +	 * | matrix[0] matrix[1] matrix[2] |
>> +	 * | matrix[3] matrix[4] matrix[5] |
>> +	 * | matrix[6] matrix[7] matrix[8] |
>> +	 */
>
>Same here.

This comment isn't actually kerneldoc, so I guess not rst either.
I can include the markup if you like, but the |s here were to indicate
it's a matrix rather than for rst.

Cheers,
-Brian

>
>>  	__s64 matrix[9];
>>  };
>
>-- 
>Jani Nikula, Intel Open Source Technology Center