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

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Message-ID: <87efzj31r2.fsf@intel.com>
Date:   Tue, 31 Jan 2017 13:30:41 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Brian Starkey <brian.starkey@....com>,
        dri-devel@...ts.freedesktop.org
Cc:     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

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.

> + *
> + *	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.

>  	__s64 matrix[9];
>  };

-- 
Jani Nikula, Intel Open Source Technology Center