linux-kernel - Re: [REGRESSION PATCH] fbdev: fbmem: behave better with small rotated displays and many CPUs

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Message-ID: <8faae5c6-ce11-99b4-4fc7-7a8925aad3e4@axentia.se>
Date:   Mon, 26 Nov 2018 14:16:37 +0000
From:   Peter Rosin <peda@...ntia.se>
To:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Fabian Frederick <ffrederick@...rs.sourceforge.net>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Geoff Levand <geoff@...radead.org>,
        James Simmons <jsimmons@...rs.sf.net>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>
Subject: Re: [REGRESSION PATCH] fbdev: fbmem: behave better with small rotated
 displays and many CPUs

Ping?!

Cheers,
Peter

On 2018-11-08 10:54, Peter Rosin wrote:
> Blitting an image with "negative" offsets is not working since there
> is no clipping. It hopefully just crashes. For the bootup logo, there
> is protection so that blitting does not happen as the image is drawn
> further and further to the right (ROTATE_UR) or further and further
> down (ROTATE_CW). There is however no protection when drawing in the
> opposite directions (ROTATE_UD and ROTATE_CCW).
> 
> Add back this protection.
> 
> The regression is 20-odd years old but the mindless warning-killing
> mentality displayed in commit 34bdb666f4b2 ("fbdev: fbmem: remove
> positive test on unsigned values") is also to blame, methinks.
> 
> Fixes: 448d479747b8 ("fbdev: fb_do_show_logo() updates")
> Signed-off-by: Peter Rosin <peda@...ntia.se>
> ---
>  drivers/video/fbdev/core/fbmem.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index bb7f5f23e347..1abeb0b72455 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -435,7 +435,9 @@ static void fb_do_show_logo(struct fb_info *info, struct fb_image *image,
>  			image->dx += image->width + 8;
>  		}
>  	} else if (rotate == FB_ROTATE_UD) {
> -		for (x = 0; x < num; x++) {
> +		u32 dx = image->dx;
> +
> +		for (x = 0; x < num && image->dx <= dx; x++) {
>  			info->fbops->fb_imageblit(info, image);
>  			image->dx -= image->width + 8;
>  		}
> @@ -447,7 +449,9 @@ static void fb_do_show_logo(struct fb_info *info, struct fb_image *image,
>  			image->dy += image->height + 8;
>  		}
>  	} else if (rotate == FB_ROTATE_CCW) {
> -		for (x = 0; x < num; x++) {
> +		u32 dy = image->dy;
> +
> +		for (x = 0; x < num && image->dy <= dy; x++) {
>  			info->fbops->fb_imageblit(info, image);
>  			image->dy -= image->height + 8;
>  		}
>