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Message-ID: <44B351CF.1090001@pol.net>
Date: Tue, 11 Jul 2006 15:22:55 +0800
From: "Antonino A. Daplas" <adaplas@pol.net>
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To: Krzysztof Halasa <khc@pm.waw.pl>
CC: "Antonino A. Daplas" <adaplas@gmail.com>,
       Jean Delvare <khali@linux-fr.org>, Andrew Morton <akpm@osdl.org>,
       lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] cirrus-logic-framebuffer-i2c-support.patch
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Krzysztof Halasa wrote:
> "Antonino A. Daplas" <adaplas@pol.net> writes:
> 
>> This is no-man's land.  Basically X grabs the VT with KD_GRAPHICS mode
>> set.  When in KD_GRAPHICS mode, the framebuffer console will not
>> send any commands to the drivers. The problem is trying to do
>> framebuffer operation while in X, we don't have any guards on that.
>> Just try fbset mymode while in X.
> 
> You mean it will not bomb?

If you pray hard enough and you do the operation while in a VC, no it
won't :-). But it's almost guaranteed to bomb if you do the framebuffer
operations while in X.

> Good, but still there is I2C question
> - can I2C accesses to the graphics chip corrupt X11 and vice versa?

That I don't know, but I doubt it.

> I can't see anything preventing that, and while we can disable
> graphic operations while Xserver is running, we can't disable I2C
> (non-DDC).

No, there's nothing to prevent simultaneous access.

> 
> Probably X11 should be disallowed to use I2C directly? I should
> probably Cc: this to XOrg as well...

X has its own i2c functionality which is completely separate from the
kernel i2c layer.

Tony