[PATCH 1/1: 2.6.15-rc5-git3] Disable ywrap if not supported by fbcon scrolling code

[PATCH 1/1: 2.6.15-rc5-git3] Disable ywrap if not supported by fbcon scrolling code

[Knut Petersen]

updatescrollmode() must not select ywrap scrolling if
divides(vc->vc_font.height, yres) is not true as this is not
supported by the actual ywrap scrolling code.

The bug is triggered with e.g. mode 800x600, vxres 1024,
vyres 8192, bpp 8, font dimensions 8x16, 8Mb video ram
and FBINFO_HWACCEL_YWRAP set. If those conditions
are met, scrolling is broken and garbage is permanently
displayed at the bottom of the screen.

No regression, no possible side effects.

Definitely needed by cyblafb and probably needed by amifb.

Signed-off-by: Knut Petersen <Knut_Petersen@t-online.de>

diff -uprN -X linux/Documentation/dontdiff -x '*.bak' -x '*.ctx' linuxorig/drivers/video/console/fbcon.c linux/drivers/video/console/fbcon.c
--- linuxorig/drivers/video/console/fbcon.c	2005-12-13 13:09:56.000000000 +0100
+++ linux/drivers/video/console/fbcon.c	2005-12-13 13:55:20.000000000 +0100
@@ -1968,7 +1968,8 @@ static __inline__ void updatescrollmode(
 		divides(ypan, vc->vc_font.height) && vyres > yres;
 	int good_wrap = (cap & FBINFO_HWACCEL_YWRAP) &&
 		divides(ywrap, vc->vc_font.height) &&
-		divides(vc->vc_font.height, vyres);
+		divides(vc->vc_font.height, vyres) &&
+		divides(vc->vc_font.height, yres);
 	int reading_fast = cap & FBINFO_READS_FAST;
 	int fast_copyarea = (cap & FBINFO_HWACCEL_COPYAREA) &&
 		!(cap & FBINFO_HWACCEL_DISABLED);




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Re: [PATCH 1/1: 2.6.15-rc5-git3] Disable ywrap if not supported by fbcon scrolling code

[Antonino A. Daplas]

Knut Petersen wrote:
> updatescrollmode() must not select ywrap scrolling if
> divides(vc->vc_font.height, yres) is not true as this is not
> supported by the actual ywrap scrolling code.
> 
> The bug is triggered with e.g. mode 800x600, vxres 1024,
> vyres 8192, bpp 8, font dimensions 8x16, 8Mb video ram
> and FBINFO_HWACCEL_YWRAP set. If those conditions
> are met, scrolling is broken and garbage is permanently
> displayed at the bottom of the screen.
> 
> No regression, no possible side effects.
> 
> Definitely needed by cyblafb and probably needed by amifb.
> 
> Signed-off-by: Knut Petersen <Knut_Petersen@t-online.de>
Acked-by: Antonino Daplas <adaplas@pol.net>


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