Hi Geert

Am 15.02.22 um 17:52 schrieb Geert Uytterhoeven:
> Add support for color-indexed frame buffer formats with two, four, and
> sixteen colors to the DRM framebuffer helper functions:
>    1. Add support for depths 1/2/4 to the damage helper,
>    2. For color-indexed modes, the length of the color bitfields must be
>       set to the color depth, else the logo code may pick a logo with too
>       many colors.  Drop the incorrect DAC width comment, which
>       originates from the i915 driver.
>    3. Accept C[124] modes when validating or filling in struct
>       fb_var_screeninfo, and  use the correct number of bits per pixel.
>    4. Set the visual to FB_VISUAL_PSEUDOCOLOR for all supported
>       color-indexed modes.
> 
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> ---
>   drivers/gpu/drm/drm_fb_helper.c | 120 +++++++++++++++++++++++++-------
>   1 file changed, 93 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index ed43b987d306afce..a4afed0de1570841 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -376,12 +376,34 @@ static void drm_fb_helper_damage_blit_real(struct drm_fb_helper *fb_helper,
>   					   struct iosys_map *dst)
>   {
>   	struct drm_framebuffer *fb = fb_helper->fb;
> -	unsigned int cpp = fb->format->cpp[0];
> -	size_t offset = clip->y1 * fb->pitches[0] + clip->x1 * cpp;
> -	void *src = fb_helper->fbdev->screen_buffer + offset;
> -	size_t len = (clip->x2 - clip->x1) * cpp;
> +	size_t offset = clip->y1 * fb->pitches[0];
> +	size_t len = clip->x2 - clip->x1;
>   	unsigned int y;
> +	void *src;
>   
> +	switch (fb->format->depth) {

The depth field is deprecated. It's probably better to use 
fb->format->format and test against 4CC codes.

> +	case 1:
> +		offset += clip->x1 / 8;
> +		len = DIV_ROUND_UP(len + clip->x1 % 8, 8);
> +		break;
> +

Style: no empty lines here.

> +	case 2:
> +		offset += clip->x1 / 4;
> +		len = DIV_ROUND_UP(len + clip->x1 % 4, 4);
> +		break;
> +
> +	case 4:
> +		offset += clip->x1 / 2;
> +		len = DIV_ROUND_UP(len + clip->x1 % 2, 2);
> +		break;
> +

Can we handle case C8 like C[124]? Seems cleaner to me.

> +	default:
> +		offset += clip->x1 * fb->format->cpp[0];
> +		len *= fb->format->cpp[0];
> +		break;
> +	}
> +
> +	src = fb_helper->fbdev->screen_buffer + offset;
>   	iosys_map_incr(dst, offset); /* go to first pixel within clip rect */
>   
>   	for (y = clip->y1; y < clip->y2; y++) {
> @@ -1231,19 +1253,30 @@ static bool drm_fb_pixel_format_equal(const struct fb_var_screeninfo *var_1,
>   }
>   
>   static void drm_fb_helper_fill_pixel_fmt(struct fb_var_screeninfo *var,
> -					 u8 depth)
> -{
> -	switch (depth) {
> -	case 8:
> +					 const struct drm_format_info *format)
> +{
> +	u8 depth = format->depth;
> +
> +	switch (format->format) {
> +	// FIXME Perhaps
> +	// #define DRM_FORMAT_C0 fourcc_code('C', '0', ' ', ' ')

What is C0?

> +	// if ((format & fourcc_code(0xff, 0xf8, 0xff, 0xff) == DRM_FORMAT_C0) ...
> +	case DRM_FORMAT_C1:
> +	case DRM_FORMAT_C2:
> +	case DRM_FORMAT_C4:
> +	case DRM_FORMAT_C8:
>   		var->red.offset = 0;
>   		var->green.offset = 0;
>   		var->blue.offset = 0;
> -		var->red.length = 8; /* 8bit DAC */
> -		var->green.length = 8;
> -		var->blue.length = 8;
> +		var->red.length = depth;
> +		var->green.length = depth;
> +		var->blue.length = depth;
>   		var->transp.offset = 0;
>   		var->transp.length = 0;
> -		break;
> +		return;
> +	}
> +
> +	switch (depth) {
>   	case 15:
>   		var->red.offset = 10;
>   		var->green.offset = 5;
> @@ -1298,7 +1331,9 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
>   {
>   	struct drm_fb_helper *fb_helper = info->par;
>   	struct drm_framebuffer *fb = fb_helper->fb;
> +	const struct drm_format_info *format = fb->format;
>   	struct drm_device *dev = fb_helper->dev;
> +	unsigned int bpp;
>   
>   	if (in_dbg_master())
>   		return -EINVAL;
> @@ -1308,22 +1343,34 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
>   		var->pixclock = 0;
>   	}
>   
> -	if ((drm_format_info_block_width(fb->format, 0) > 1) ||
> -	    (drm_format_info_block_height(fb->format, 0) > 1))
> -		return -EINVAL;
> +	switch (format->format) {
> +	case DRM_FORMAT_C1:
> +	case DRM_FORMAT_C2:
> +	case DRM_FORMAT_C4:
> +		bpp = format->depth;
> +		break;

Added C8 here would be more consistent.

> +
> +	default:
> +		if ((drm_format_info_block_width(format, 0) > 1) ||
> +		    (drm_format_info_block_height(format, 0) > 1))
> +			return -EINVAL;
> +
> +		bpp = format->cpp[0] * 8;
> +		break;
> +	}
>   
>   	/*
>   	 * Changes struct fb_var_screeninfo are currently not pushed back
>   	 * to KMS, hence fail if different settings are requested.
>   	 */
> -	if (var->bits_per_pixel > fb->format->cpp[0] * 8 ||
> +	if (var->bits_per_pixel > bpp ||
>   	    var->xres > fb->width || var->yres > fb->height ||
>   	    var->xres_virtual > fb->width || var->yres_virtual > fb->height) {
>   		drm_dbg_kms(dev, "fb requested width/height/bpp can't fit in current fb "
>   			  "request %dx%d-%d (virtual %dx%d) > %dx%d-%d\n",
>   			  var->xres, var->yres, var->bits_per_pixel,
>   			  var->xres_virtual, var->yres_virtual,
> -			  fb->width, fb->height, fb->format->cpp[0] * 8);
> +			  fb->width, fb->height, bpp);
>   		return -EINVAL;
>   	}
>   
> @@ -1338,13 +1385,13 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
>   	    !var->blue.length    && !var->transp.length   &&
>   	    !var->red.msb_right  && !var->green.msb_right &&
>   	    !var->blue.msb_right && !var->transp.msb_right) {
> -		drm_fb_helper_fill_pixel_fmt(var, fb->format->depth);
> +		drm_fb_helper_fill_pixel_fmt(var, format);
>   	}
>   
>   	/*
>   	 * Likewise, bits_per_pixel should be rounded up to a supported value.
>   	 */
> -	var->bits_per_pixel = fb->format->cpp[0] * 8;
> +	var->bits_per_pixel = bpp;
>   
>   	/*
>   	 * drm fbdev emulation doesn't support changing the pixel format at all,
> @@ -1680,11 +1727,20 @@ 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,
> -				   uint32_t depth)
> +				   uint32_t format)
>   {
>   	info->fix.type = FB_TYPE_PACKED_PIXELS;
> -	info->fix.visual = depth == 8 ? FB_VISUAL_PSEUDOCOLOR :
> -		FB_VISUAL_TRUECOLOR;
> +	switch (format) {
> +	case DRM_FORMAT_C1:
> +	case DRM_FORMAT_C2:
> +	case DRM_FORMAT_C4:
> +	case DRM_FORMAT_C8:
> +		info->fix.visual = FB_VISUAL_PSEUDOCOLOR;
> +		break;
> +	default:
> +		info->fix.visual = FB_VISUAL_TRUECOLOR;
> +		break;
> +	}
>   	info->fix.mmio_start = 0;
>   	info->fix.mmio_len = 0;
>   	info->fix.type_aux = 0;
> @@ -1701,19 +1757,29 @@ static void drm_fb_helper_fill_var(struct fb_info *info,
>   				   uint32_t fb_width, uint32_t fb_height)
>   {
>   	struct drm_framebuffer *fb = fb_helper->fb;
> +	const struct drm_format_info *format = fb->format;
>   
> -	WARN_ON((drm_format_info_block_width(fb->format, 0) > 1) ||
> -		(drm_format_info_block_height(fb->format, 0) > 1));
>   	info->pseudo_palette = fb_helper->pseudo_palette;
>   	info->var.xres_virtual = fb->width;
>   	info->var.yres_virtual = fb->height;
> -	info->var.bits_per_pixel = fb->format->cpp[0] * 8;
> +	switch (format->format) {
> +	case DRM_FORMAT_C1:
> +	case DRM_FORMAT_C2:
> +	case DRM_FORMAT_C4:
> +		info->var.bits_per_pixel = format->depth;
> +		break;

C8.


The fbdev helpers look correct to me.  I'm not so sure about the usage 
of the format info; especially the depth field.  The docs say that the 
field is deprecated and should be 0. Maybe depth can be handled within 
fbdev?

Best regards
Thomas

> +
> +	default:
> +		WARN_ON((drm_format_info_block_width(format, 0) > 1) ||
> +			(drm_format_info_block_height(format, 0) > 1));
> +		info->var.bits_per_pixel = format->cpp[0] * 8;
> +	}
>   	info->var.accel_flags = FB_ACCELF_TEXT;
>   	info->var.xoffset = 0;
>   	info->var.yoffset = 0;
>   	info->var.activate = FB_ACTIVATE_NOW;
>   
> -	drm_fb_helper_fill_pixel_fmt(&info->var, fb->format->depth);
> +	drm_fb_helper_fill_pixel_fmt(&info->var, format);
>   
>   	info->var.xres = fb_width;
>   	info->var.yres = fb_height;
> @@ -1738,7 +1804,7 @@ 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->depth);
> +	drm_fb_helper_fill_fix(info, fb->pitches[0], fb->format->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
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev