linux-kernel - Re: [PATCH, RFC] adjust legacy IDE resource setting

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Date:	Wed, 14 Feb 2007 15:46:49 +0000
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	"Alan" <alan@...rguk.ukuu.org.uk>
Cc:	<alan@...hat.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH, RFC] adjust legacy IDE resource setting

>>> Alan <alan@...rguk.ukuu.org.uk> 14.02.07 16:40 >>>
>On Wed, 14 Feb 2007 15:05:24 +0000
>"Jan Beulich" <jbeulich@...ell.com> wrote:
>
>> The change to force legacy mode IDE channels' resources to fixed
>> non-zero values confuses (at least some versions of) X, because the
>> values reported by the kernel and those readable from PCI config space
>> aren't consistent anymore. Therefore, this patch arranges for the
>> respective BARs to also get updated if possible.
>
>If X is getting confused fix X. Those BARs are *undefined* in legacy
>mode. The value in them is undefined, the results that end up there if
>you do write to them are undefined too. If X believes those BAR values
>blindly it'll do the wrong thing in some freaky cases.
>
>Which specific versions of X are problematic ?

The one I ran into problems with is reporting

X Window System Version 6.9.0
Release Date: 21 December 2005

(used in SLES10, the specific package version is xorg-x11-6.9.0-50.14)

>As to the implementation:
>	start and end as passed are the real I/O values so you don't need
>to mask them that I can see.

The masking is done primarily to (a) calculate the correct length (from a BAR's
perspective), as I don't want to write the BAR if its length doesn't match the
expectation, and (b) to properly report the new value in the printk.

>I've no fundamental problem with writing the BAR values back to avoid
>confusing some apparently broken X, but I'd like to know what X, what
>circumstances and that X is also getting fixed.

Of course I also opened a bug against X, as I too think it's doing something
wrong here.

Jan
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