linux-kernel - Re: [PATCH] framebuffer: fix screen corruption when copying

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Date:	Wed, 17 Sep 2014 07:44:14 -0400 (EDT)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
cc:	Tomi Valkeinen <tomi.valkeinen@...com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] framebuffer: fix screen corruption when copying



On Wed, 17 Sep 2014, Geert Uytterhoeven wrote:

> Hi Mikulas,
> 
> On Tue, Sep 16, 2014 at 6:38 PM, Mikulas Patocka <mpatocka@...hat.com> wrote:
> > The patch also removes the references to fb_memmove in the code that is
> > commented out because fb_memmove was removed from framebuffer subsystem.
> 
> I'd leave it as-is. Using plain memmove() is not correct, as it should operate
> on MMIO space, not RAM. On x86 it works with memmove(), though, but
> not on all architectures.
> 
> Gr{oetje,eeting}s,
> 
>                         Geert

That code is disabled with #if 0. So it doesn't matter if it's incorrect 
in some specific situation.

The purpose of that disabled code is to be able to verify that the bug is 
in bitcpy_rev. I get screen corruption - so I enable that "memmove" 
statement - the screen corruption goes away - so I know that the bug is in 
bitcpy_rev.

Mikulas
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