linux-kernel - Re: X display shift with disabled console blanking

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Message-ID: <463763B8.7060606@moving-picture.com>
Date:	Tue, 01 May 2007 16:58:48 +0100
From:	James Pearson <james-p@...ing-picture.com>
To:	"Antonino A. Daplas" <adaplas@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: X display shift with disabled console blanking

Antonino A. Daplas wrote:
> On Tue, 2007-05-01 at 13:17 +0100, James Pearson wrote:
> 
>>Antonino A. Daplas wrote:
>>
>>>On Mon, 2007-04-30 at 13:58 +0100, James Pearson wrote:
>>>
>>>
>>>>Antonino A. Daplas wrote:
>>>>
>>>>
>>>>>On Fri, 2007-04-27 at 18:08 +0100, James Pearson wrote:
> 
> 
>>It does indeed seem that the switching back and forth between text and 
>>graphics does appear to be part of the issue - in my previous testing I 
>>probably did do this (but didn't include this in my recipe above) - so 
>>here is a new 'recipe' that shows the problem (for me)
>>
>>boot to run level 3
>>
>>if not root, then make sure /dev/console is writeable
>>
>>login and type:
>>
>>setterm -blank 0
>>
>>start X
>>
>>type into an xterm:
>>
>>while true; do echo "" > /dev/console; usleep 100000; done
>>
>>while the above loop is running switch to the text console and back 
>>again (Ctrl-Alt-F1 then Ctrl-Alt-F7)
>>
>>... and the screen will be shifting (and wrapping) to the left.
>>
> 
> 
> Okay, this makes me see the problem more clearly.  It looks like that
> vt/console layer is unreliable in terms of checking for the
> text/graphics mode of the current console.  Instead of auditing the
> console code, I'll just have vgacon check for the mode.  Try the
> attached patch and let me know if it helps. 

That seems to fix it!

Thanks

James Pearson
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