Re: [RFC] VBE DDC bios call stalls boot

From: Yum Rayan
Date: Mon Apr 24 2006 - 03:27:18 EST


> > Is this how your patch looked when you tried this ?
>
> I've discovered that checking for availability does not give any added benefit,
> but this is the correct approach and I have to agree with this patch.

My patch was similar. I referenced
http://www.vesa.org/public/VBE/VBEDDC11.PDF. Differences were the
finer look up of the ambiguous status code and setting up ES:DI to be
NULL before call to INT 10h, as follows:

--- linux-2.6.15.4.a/arch/i386/boot/video.S 2006-02-09 23:22:48.000000000 -0800
+++ linux-2.6.15.4.b/arch/i386/boot/video.S 2006-04-24 00:07:08.000000000 -0700
@@ -1946,6 +1946,22 @@ store_edid:
rep
stosl

+ pushw %es
+ movw $0x4f15, %ax # report VBE/DDC capabilities
+ xorw %bx, %bx
+ xorw %cx, %cx
+ xorw %di, %di
+ pushw %di
+ popw %es
+ int $0x10
+ popw %es
+
+ cmpb $0x0, %ah # function call failed
+ jne no_edid
+
+ cmpb $0x4f, %al # function not supported
+ jne no_edid
+
movw $0x4f15, %ax # do VBE/DDC
movw $0x01, %bx
movw $0x00, %cx
@@ -1953,6 +1969,7 @@ store_edid:
movw $0x140, %di
int $0x10

+no_edid:
popw %di # restore all registers
popw %dx
popw %cx


> This option is new and not yet available in 2.6.15, so you may have
> to use your patch temporarily.

I was able to download a more recent kernel and configure
CONFIG_FB_FIRMWARE_EDID. Thanks.
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