linux-kernel - Re: [PATCH] drm/ssd130x: Change pixel format used to compute the buffer size

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Date:   Thu, 13 Jul 2023 12:06:47 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Javier Martinez Canillas <javierm@...hat.com>,
        linux-kernel@...r.kernel.org
Cc:     dri-devel@...ts.freedesktop.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH] drm/ssd130x: Change pixel format used to compute the
 buffer size



Am 13.07.23 um 10:58 schrieb Javier Martinez Canillas:
> The commit e254b584dbc0 ("drm/ssd130x: Remove hardcoded bits-per-pixel in
> ssd130x_buf_alloc()") used a pixel format info instead of a hardcoded bpp
> to calculate the size of the buffer allocated to store the native pixels.
> 
> But that wrongly used the DRM_FORMAT_C1 fourcc pixel format, which is for
> color-indexed frame buffer formats. While the ssd103x controllers don't
> support different single-channel colors nor a Color Lookup Table (CLUT).

Makes sense to me.

Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>

> 
> Both formats use eight pixels/byte, so in practice there is no functional
> changes in this patch. But still the correct pixel format should be used.
> 
> Suggested-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
> ---
> 
>   drivers/gpu/drm/solomon/ssd130x.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/solomon/ssd130x.c b/drivers/gpu/drm/solomon/ssd130x.c
> index b3dc1ca9dc10..afb08a8aa9fc 100644
> --- a/drivers/gpu/drm/solomon/ssd130x.c
> +++ b/drivers/gpu/drm/solomon/ssd130x.c
> @@ -153,7 +153,7 @@ static int ssd130x_buf_alloc(struct ssd130x_device *ssd130x)
>   	const struct drm_format_info *fi;
>   	unsigned int pitch;
>   
> -	fi = drm_format_info(DRM_FORMAT_C1);
> +	fi = drm_format_info(DRM_FORMAT_R1);
>   	if (!fi)
>   		return -EINVAL;
>   

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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