Re: [PATCH] Add fb_check_var() for fixed mode device.

[Geert Uytterhoeven <geert@linux-m68k.org>]

On Fri, 29 Aug 2008, Takashi Yoshii wrote:
> Sounds good.
> > 4. Provide a generic check_var() that does some basic sanity checking
> > against info->var (eg. check xres, yres and bits_per_pixel).
> How about this.
> Any comments? Expecially about what to check, what to restore.
> 
> Cheers,
> /yoshii # Restoring pixclock would be a workaround for Xorg issue :)
> 
> drivers/video/fbmem.c:fb_check_var()
>  New function for fixed mode device which doesn't provide its own
>  check_var function.
> 
> Signed-off-by: Takashi YOSHII <yoshii.takashi@renesas.com>
> 
> diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
> index c6b8e92..ff94eaf 100644
> --- a/drivers/video/fbmem.c
> +++ b/drivers/video/fbmem.c
> @@ -904,6 +904,56 @@ static int fb_check_caps(struct fb_info *info, struct fb_var_screeninfo *var,
>  	return err;
>  }
>  
> +/* Sanity check for drivers which can't change video mode */
> +static int
> +fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
> +{
> +	struct fb_var_screeninfo *constant = &info->var;
> +        __u32 xoffset = var->xoffset;
> +	__u32 yoffset = var->yoffset;
> +	__u32 activate = var->activate;
> +	__u32 yres = (constant->vmode & FB_VMODE_YWRAP)? 0: var->yres; 
> +
> +	/* do round _up_ */
> +	if (var->xres_virtual < xoffset + var->xres)
> +		var->xres_virtual = xoffset + var->xres;
> +	if (var->yres_virtual < yoffset + yres)
> +		var->yres_virtual = yoffset + yres;

Why this part? var->[xy]res{,_virtual} will be overwritten by the
correct values later anyway.

> +	/* pan is acceptable only if we have fb_pan_display) */
> +	if ( (var->yoffset || var->xoffset) && !info->fbops->fb_pan_display )
> +		return -EINVAL;

You should validate var->[xy]offset against constant->[xy]res_virtual
and info->fix.[xy]{pan,wrap}step.

> +	/* copy most */
> +	*var = *constant;
> +	/* resotore some that are not a part of viede mode */
           ^^^^^^^^
	   restore
> +	var->xoffset = xoffset;
> +	var->yoffset = yoffset;
> +	var->activate = activate;
> +
> +	return 0;
> +}

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

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