linux-kernel - Re: [PATCH v2] drm/format-helper: Make conversion_buf

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Message-ID: <cd7c5dfa-0650-05c0-96ac-baf1fd397e3c@igalia.com>
Date:   Thu, 9 Mar 2023 19:34:41 -0300
From:   Maíra Canal <mcanal@...lia.com>
To:     Javier Martinez Canillas <javierm@...hat.com>,
        linux-kernel@...r.kernel.org
Cc:     Arthur Grillo <arthurgrillo@...eup.net>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Maxime Ripard <maxime@...no.tech>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        David Gow <davidgow@...gle.com>,
        José Expósito <jose.exposito89@...il.com>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2] drm/format-helper: Make conversion_buf_size() support
 sub-byte pixel fmts

On 3/7/23 18:50, Javier Martinez Canillas wrote:
> There are DRM fourcc formats that have pixels smaller than a byte, but the
> conversion_buf_size() function assumes that pixels are a multiple of bytes
> and use the struct drm_format_info .cpp field to calculate the dst_pitch.
> 
> Instead, calculate it by using the bits per pixel (bpp) and divide it by 8
> to account for formats that have sub-byte pixels.
> 
> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>

Reviewed-by: Maíra Canal <mcanal@...lia.com>

Best Regards,
- Maíra Canal

> ---
> Tested by making sure that the following command still succeeds:
> 
> ./tools/testing/kunit/kunit.py run \
> --kunitconfig=drivers/gpu/drm/tests/.kunitconfig
> 
> Changes in v2:
> - Drop an unused variable, that was pointed out by the kernel robot.
> 
>   drivers/gpu/drm/tests/drm_format_helper_test.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tests/drm_format_helper_test.c b/drivers/gpu/drm/tests/drm_format_helper_test.c
> index 9536829c6e3a..84b5cc29c8fc 100644
> --- a/drivers/gpu/drm/tests/drm_format_helper_test.c
> +++ b/drivers/gpu/drm/tests/drm_format_helper_test.c
> @@ -409,12 +409,15 @@ static size_t conversion_buf_size(u32 dst_format, unsigned int dst_pitch,
>   				  const struct drm_rect *clip)
>   {
>   	const struct drm_format_info *dst_fi = drm_format_info(dst_format);
> +	unsigned int bpp;
>   
>   	if (!dst_fi)
>   		return -EINVAL;
>   
> -	if (!dst_pitch)
> -		dst_pitch = drm_rect_width(clip) * dst_fi->cpp[0];
> +	if (!dst_pitch) {
> +		bpp = drm_format_info_bpp(dst_fi, 0);
> +		dst_pitch = DIV_ROUND_UP(drm_rect_width(clip) * bpp, 8);
> +	}
>   
>   	return dst_pitch * drm_rect_height(clip);
>   }