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SubjectRe: [PATCH] Don't probe for DDC on VBE1.2
On Thu, 15 Feb 2007 08:29:49 -0800 (PST) Zwane Mwaikambo <zwane@infradead.org> wrote:

> VBE1.2 doesn't support function 15h (DDC) resulting in a 'hang' whilst
> uncompressing kernel with some video cards. Make sure we check VBE version
> before fiddling around with DDC.
>
> http://bugzilla.kernel.org/show_bug.cgi?id=1458
>
> Opened: 2003-10-30 09:12 Last update: 2007-02-13 22:03
>
> :(
>
> Much thanks to Tobias Hain for help in testing and investigating the bug.
> Tested on;
>
> i386, Chips & Technologies 65548 VESA VBE 1.2
> CONFIG_VIDEO_SELECT=Y
> CONFIG_FIRMWARE_EDID=Y
>
> Untested on x86_64.
>
> Signed-off-by: Zwane Mwaikambo <zwane@infradead.org>
>
> Index: linux-2.6.20-rc6-mm1/arch/i386/boot/video.S
> ===================================================================
> RCS file: /home/cvsroot/linux-2.6.20-rc6-mm1/arch/i386/boot/video.S,v
> retrieving revision 1.1.1.1
> diff -u -p -B -r1.1.1.1 video.S
> --- linux-2.6.20-rc6-mm1/arch/i386/boot/video.S 30 Jan 2007 05:28:31 -0000 1.1.1.1
> +++ linux-2.6.20-rc6-mm1/arch/i386/boot/video.S 15 Feb 2007 16:27:32 -0000
> @@ -1945,6 +1945,20 @@ store_edid:
> rep
> stosl
>
> + pushw %es
> + pushw %ds
> + popw %es
> + leaw modelist+1024, %di
> + movw $0x4f00, %ax
> + int $0x10
> + popw %es
> +
> + cmpw $0x004f, %ax
> + jne no_edid
> +
> + cmpw $0x0102, 4(%di) # only do EDID on > 1.2
> + je no_edid
> +
> pushw %es # save ES
> xorw %di, %di # Report Capability
> pushw %di

This makes the long-suffering-but-vigorously-defended Vaio come up with a
black display. Everything's working OK otherwise. Sort of a Black Screen
of Life. I wouldn't call it an improvement though.
-
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