Re: [PATCH v2 7/8] drm/fb-helper: Add support for DRM_FORMAT_R1

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 24.08.23 um 17:08 schrieb Geert Uytterhoeven:
> Add support for the monochrome light-on-dark buffer format (R1) to the
> fb helper, so this format can be used for fbdev emulation and for the
> text console.  This avoids the overhead of using XR24 and the associated
> conversions on display hardware that supports only a simple monochrome
> format.
> 
> R1 is very similar to C1 (monochrome indexed color), and shares the same
> depth and bpp.  As drm_mode_legacy_fb_format() returns a format based on
> only depth and bpp, it cannot distinguish between R1 and C1.  Hence

Could we rather add another parameter to drm_mode_legacy_fb_format(); 
say 'bool indexed'. If set to true, it prefers _Cx formats, otherwise _Rx.

The parameter would be 'true' for most calls; except in 
drm_fb_helper_find_format(). There, we can go through the array of given 
formats and check if there's one that has is_color_indexed set. If so, 
we specify true, if not we specify false.

Best regards
Thomas

> drm_fb_helper_find_format() is modified to try to fall back to R1 if C1
> is not supported.
> 
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
> Tested-by: Javier Martinez Canillas <javierm@redhat.com>
> ---
> v2:
>    - Add Reviewed-by, Tested-by.
> ---
>   drivers/gpu/drm/drm_fb_helper.c | 41 ++++++++++++++++++++++++---------
>   1 file changed, 30 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 4dc28fdcc1e0a6a4..71baf8597516e9fd 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -1130,7 +1130,7 @@ static void drm_fb_helper_fill_pixel_fmt(struct fb_var_screeninfo *var,
>   {
>   	u8 depth = format->depth;
>   
> -	if (format->is_color_indexed) {
> +	if (format->format == DRM_FORMAT_R1 || format->is_color_indexed) {
>   		var->red.offset = 0;
>   		var->green.offset = 0;
>   		var->blue.offset = 0;
> @@ -1236,6 +1236,7 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
>   	case DRM_FORMAT_C1:
>   	case DRM_FORMAT_C2:
>   	case DRM_FORMAT_C4:
> +	case DRM_FORMAT_R1:
>   		/* supported format with sub-byte pixels */
>   		break;
>   
> @@ -1439,12 +1440,24 @@ int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
>   }
>   EXPORT_SYMBOL(drm_fb_helper_pan_display);
>   
> +static bool is_supported_format(uint32_t format, const uint32_t *formats,
> +				size_t format_count)
> +{
> +	size_t i;
> +
> +	for (i = 0; i < format_count; ++i) {
> +		if (formats[i] == format)
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
>   static uint32_t drm_fb_helper_find_format(struct drm_fb_helper *fb_helper, const uint32_t *formats,
>   					  size_t format_count, uint32_t bpp, uint32_t depth)
>   {
>   	struct drm_device *dev = fb_helper->dev;
>   	uint32_t format;
> -	size_t i;
>   
>   	/*
>   	 * Do not consider YUV or other complicated formats
> @@ -1457,10 +1470,12 @@ static uint32_t drm_fb_helper_find_format(struct drm_fb_helper *fb_helper, const
>   	if (!format)
>   		goto err;
>   
> -	for (i = 0; i < format_count; ++i) {
> -		if (formats[i] == format)
> -			return format;
> -	}
> +	if (is_supported_format(format, formats, format_count))
> +		return format;
> +
> +	if (format == DRM_FORMAT_C1 &&
> +	    is_supported_format(DRM_FORMAT_R1, formats, format_count))
> +		return DRM_FORMAT_R1;
>   
>   err:
>   	/* We found nothing. */
> @@ -1680,11 +1695,15 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
>   }
>   
>   static void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
> -				   bool is_color_indexed)
> +				   const struct drm_format_info *format)
>   {
>   	info->fix.type = FB_TYPE_PACKED_PIXELS;
> -	info->fix.visual = is_color_indexed ? FB_VISUAL_PSEUDOCOLOR
> -					    : FB_VISUAL_TRUECOLOR;
> +	if (format->format == DRM_FORMAT_R1)
> +		info->fix.visual = FB_VISUAL_MONO10;
> +	else if (format->is_color_indexed)
> +		info->fix.visual = FB_VISUAL_PSEUDOCOLOR;
> +	else
> +		info->fix.visual = FB_VISUAL_TRUECOLOR;
>   	info->fix.mmio_start = 0;
>   	info->fix.mmio_len = 0;
>   	info->fix.type_aux = 0;
> @@ -1707,6 +1726,7 @@ static void drm_fb_helper_fill_var(struct fb_info *info,
>   	case DRM_FORMAT_C1:
>   	case DRM_FORMAT_C2:
>   	case DRM_FORMAT_C4:
> +	case DRM_FORMAT_R1:
>   		/* supported format with sub-byte pixels */
>   		break;
>   
> @@ -1747,8 +1767,7 @@ void drm_fb_helper_fill_info(struct fb_info *info,
>   {
>   	struct drm_framebuffer *fb = fb_helper->fb;
>   
> -	drm_fb_helper_fill_fix(info, fb->pitches[0],
> -			       fb->format->is_color_indexed);
> +	drm_fb_helper_fill_fix(info, fb->pitches[0], fb->format);
>   	drm_fb_helper_fill_var(info, fb_helper,
>   			       sizes->fb_width, sizes->fb_height);
>   

-- 
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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