linux-kernel - Re: [PATCH v5 1/6] drm/format-helper: Add drm_fb_xrgb8888_to_gray8

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Date:   Fri, 11 Feb 2022 17:58:44 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        linux-fbdev@...r.kernel.org, Sam Ravnborg <sam@...nborg.org>,
        Maxime Ripard <maxime@...no.tech>,
        dri-devel@...ts.freedesktop.org,
        Noralf Trønnes <noralf@...nnes.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>
Subject: Re: [PATCH v5 1/6] drm/format-helper: Add
 drm_fb_xrgb8888_to_gray8_line()

On Fri, Feb 11, 2022 at 03:33:53PM +0100, Javier Martinez Canillas wrote:
> Pull the per-line conversion logic into a separate helper function.
> 
> This will allow to do line-by-line conversion in other helpers that
> convert to a gray8 format.

for-loop vs. while-loop is not critical, so
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> Suggested-by: Thomas Zimmermann <tzimmermann@...e.de>
> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
> Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
> ---
> 
> Changes in v5:
> - Add Thomas Zimmermann's Reviewed-by to patch #1.
> 
> Changes in v3:
> - Add a drm_fb_xrgb8888_to_gray8_line() helper function (Thomas Zimmermann)
> 
>  drivers/gpu/drm/drm_format_helper.c | 31 ++++++++++++++++++-----------
>  1 file changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
> index 0f28dd2bdd72..b981712623d3 100644
> --- a/drivers/gpu/drm/drm_format_helper.c
> +++ b/drivers/gpu/drm/drm_format_helper.c
> @@ -464,6 +464,21 @@ void drm_fb_xrgb8888_to_xrgb2101010_toio(void __iomem *dst,
>  }
>  EXPORT_SYMBOL(drm_fb_xrgb8888_to_xrgb2101010_toio);
>  
> +static void drm_fb_xrgb8888_to_gray8_line(u8 *dst, const u32 *src, unsigned int pixels)
> +{
> +	unsigned int x;
> +
> +	for (x = 0; x < pixels; x++) {
> +		u8 r = (*src & 0x00ff0000) >> 16;
> +		u8 g = (*src & 0x0000ff00) >> 8;
> +		u8 b =  *src & 0x000000ff;
> +
> +		/* ITU BT.601: Y = 0.299 R + 0.587 G + 0.114 B */
> +		*dst++ = (3 * r + 6 * g + b) / 10;
> +		src++;
> +	}
> +}
> +
>  /**
>   * drm_fb_xrgb8888_to_gray8 - Convert XRGB8888 to grayscale
>   * @dst: 8-bit grayscale destination buffer
> @@ -484,8 +499,9 @@ EXPORT_SYMBOL(drm_fb_xrgb8888_to_xrgb2101010_toio);
>  void drm_fb_xrgb8888_to_gray8(void *dst, unsigned int dst_pitch, const void *vaddr,
>  			      const struct drm_framebuffer *fb, const struct drm_rect *clip)
>  {
> -	unsigned int len = (clip->x2 - clip->x1) * sizeof(u32);
> -	unsigned int x, y;
> +	unsigned int linepixels = clip->x2 - clip->x1;
> +	unsigned int len = linepixels * sizeof(u32);
> +	unsigned int y;
>  	void *buf;
>  	u8 *dst8;
>  	u32 *src32;
> @@ -508,16 +524,7 @@ void drm_fb_xrgb8888_to_gray8(void *dst, unsigned int dst_pitch, const void *vad
>  	for (y = clip->y1; y < clip->y2; y++) {
>  		dst8 = dst;
>  		src32 = memcpy(buf, vaddr, len);
> -		for (x = clip->x1; x < clip->x2; x++) {
> -			u8 r = (*src32 & 0x00ff0000) >> 16;
> -			u8 g = (*src32 & 0x0000ff00) >> 8;
> -			u8 b =  *src32 & 0x000000ff;
> -
> -			/* ITU BT.601: Y = 0.299 R + 0.587 G + 0.114 B */
> -			*dst8++ = (3 * r + 6 * g + b) / 10;
> -			src32++;
> -		}
> -
> +		drm_fb_xrgb8888_to_gray8_line(dst8, src32, linepixels);
>  		vaddr += fb->pitches[0];
>  		dst += dst_pitch;
>  	}
> -- 
> 2.34.1
> 

-- 
With Best Regards,
Andy Shevchenko