[PATCH] x86: 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>
Signed-off-by: Andi Kleen <ak@suse.de>

arch/i386/boot/video.S

@@ -571,6 +571,16 @@ setr1:	lodsw
 	jmp	_m_s
 
 check_vesa:
+#ifdef CONFIG_FIRMWARE_EDID
+	leaw	modelist+1024, %di
+	movw	$0x4f00, %ax
+	int	$0x10
+	cmpw	$0x004f, %ax
+	jnz	setbad
+
+	movw	4(%di), %ax
+	movw	%ax, vbe_version
+#endif
 	leaw	modelist+1024, %di
 	subb	$VIDEO_FIRST_VESA>>8, %bh
 	movw	%bx, %cx			# Get mode information structure
@@ -1945,6 +1955,9 @@ store_edid:
 	rep
 	stosl
 
+	cmpw	$0x0200, vbe_version		# only do EDID on >= VBE2.0
+	jl	no_edid
+
 	pushw   %es				# save ES
 	xorw    %di, %di                        # Report Capability
 	pushw   %di
@@ -1987,6 +2000,7 @@ do_restore:	.byte	0	# Screen contents altered during mode change
 svga_prefix:	.byte	VIDEO_FIRST_BIOS>>8	# Default prefix for BIOS modes
 graphic_mode:	.byte	0	# Graphic mode with a linear frame buffer
 dac_size:	.byte	6	# DAC bit depth
+vbe_version:	.word	0	# VBE bios version
 
 # Status messages
 keymsg:		.ascii	"Press <RETURN> to see video modes available, "

arch/x86_64/boot/video.S

@@ -571,6 +571,16 @@ setr1:	lodsw
 	jmp	_m_s
 
 check_vesa:
+#ifdef CONFIG_FIRMWARE_EDID
+	leaw	modelist+1024, %di
+	movw	$0x4f00, %ax
+	int	$0x10
+	cmpw	$0x004f, %ax
+	jnz	setbad
+
+	movw	4(%di), %ax
+	movw	%ax, vbe_version
+#endif
 	leaw	modelist+1024, %di
 	subb	$VIDEO_FIRST_VESA>>8, %bh
 	movw	%bx, %cx			# Get mode information structure
@@ -1945,6 +1955,9 @@ store_edid:
 	rep
 	stosl
 
+	cmpw	$0x0200, vbe_version		# only do EDID on >= VBE2.0
+	jl	no_edid
+
 	pushw   %es				# save ES
 	xorw    %di, %di                        # Report Capability
 	pushw   %di
@@ -1987,6 +2000,7 @@ do_restore:	.byte	0	# Screen contents altered during mode change
 svga_prefix:	.byte	VIDEO_FIRST_BIOS>>8	# Default prefix for BIOS modes
 graphic_mode:	.byte	0	# Graphic mode with a linear frame buffer
 dac_size:	.byte	6	# DAC bit depth
+vbe_version:	.word	0	# VBE bios version
 
 # Status messages
 keymsg:		.ascii	"Press <RETURN> to see video modes available, "