linux-kernel - Re: [PATCH] retrieve VBE EDID/DDC info independent of used video mode

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Date:	Tue, 10 Jul 2007 10:23:45 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Daniel Drake <dsd@...too.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Beulich <jbeulich@...ell.com>,
	linux-kernel@...r.kernel.org, zwane@...radead.org,
	Andi Kleen <ak@...e.de>, "Antonino A. Daplas" <adaplas@....net>
Subject: Re: [PATCH] retrieve VBE EDID/DDC info independent of used video
 mode

Daniel Drake wrote:
> H. Peter Anvin wrote:
>> User error.
>> Please replace user and press any key.
>>
>> # CONFIG_FIRMWARE_EDID is not set
>>
>> The user has *explicitly* disabled acquisition of EDID from the
>> firmware, so of course it doesn't probe for it.
> 
> I'm not versed with all this EDID and resolution stuff, but shouldn't
> the resolution be detected correctly under all configurations?

Not if you actively disable detection!

Why would you want to be able to disable detection?  Well, your BIOS
might be buggy.

> The original problem is that as of 2.6.20.11, the resolution is
> misdetected - it is wrong by 6 pixels. The same configuration with
> 2.6.20.10 works fine.

That is because 2.6.20.11 incorrectly disabled EDID detection when a
non-VESA mode was chosen as the initial mode.  This is a bug.

> With the 2.6.20.10/2.6.20.11 configuration, the user did have
> CONFIG_FIRMWARE_EDID set. I'm not sure why he changed this for the -mm
> testing, but then again I don't understand why it should matter.

You're complaining that we didn't query EDID when you *explicitly* asked
us not to.  This is not a bug!

	-hpa
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