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Subject[PATCH] Don't probe for DDC on VBE1.2
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
Index: linux-2.6.20-rc6-mm1/arch/x86_64/boot/video.S
===================================================================
RCS file: /home/cvsroot/linux-2.6.20-rc6-mm1/arch/x86_64/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/x86_64/boot/video.S 30 Jan 2007 05:28:36 -0000 1.1.1.1
+++ linux-2.6.20-rc6-mm1/arch/x86_64/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
-
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