Re: [PATCH 1/8] fbcon: Do not touch hardware if vc_mode != KD_TEXT

[Andrew Morton <akpm@osdl.org>]

"Antonino A. Daplas" <adaplas@hotpop.com> wrote:
>
> Sigh, this patch uncovered a can of worms.  I tested different combinations,
> those with/without xxxfb_blank implementation, framebuffers in directcolor
> or truecolor, etc. I find that there is a problem unblanking if the hardware
> has no xxxfb_blank() implementation, and also that the generic fb_blank() in
> fbmem.c is problematic with drivers in directcolor or pseudocolor mode when
> called by an fb application such as X.
> 
> Display blanking is implemented in three ways:
> 
>     1. using the drivers blanking implementation - info->fbops->fb_blank()
>     2. clearing the screen with the console erase character - fbcon_blank()
>     3. setting the color map to all black - fb_blank()
> 
> The third method is problematic for these reasons:
> 
>     - Setting the colormap to all black will not work in truecolor mode
>     - In directcolor or pseudocolor, it will overwrite the fb application's
>       color map, producing wrong colors.
> 
> So, remove the generic implementation in fb_blank() and just return -EINVAL
> if there is no hardware implementation.  This will be only used by apps doing
> an FBIO_BLANK ioctl, and is a more robust approach.

This patch conflicts with Ben's "fbdev: workaround for broken X servers"
patch, which is in Linus's tree now.

So fb_blank() will now look like this:

int
fb_blank(struct fb_info *info, int blank)
{	
	int err = -EINVAL;
	
	/* Workaround for broken X servers */
	if (blank > VESA_POWERDOWN)
		blank = VESA_POWERDOWN;

	if (info->fbops->fb_blank)
 		err = info->fbops->fb_blank(blank, info);

	return err;
}



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