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

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Date:	Sat, 30 Jun 2007 18:25:31 -0400
From:	Daniel Drake <dsd@...too.org>
To:	Jan Beulich <jbeulich@...ell.com>
CC:	linux-kernel@...r.kernel.org, Andrew Morton <akpm@...l.org>,
	zwane@...radead.org, Andi Kleen <ak@...e.de>
Subject: Re: [PATCH] retrieve VBE EDID/DDC info independent of used video
 mode

Jan Beulich wrote:
> The code to retrieve this information was (a) inside a CONFIG_VIDEO_SELECT
> section and (b) protected by a check of a variable (vbe_version) that
> would get initialized only when a VESA mode was selected on the command
> line.

This patch solves a 2.6.20.11 (and 2.6.21) regression added by the patch 
titled "x86: Don't probe for DDC on VBE1.2"

The regression caused the screen resolution to be incorrectly adjusted 
by 6 pixels. This patch makes it go back to normal again.

https://bugs.gentoo.org/show_bug.cgi?id=181067

Please apply this patch or discuss further :)

> Signed-off-by: Jan Beulich <jbeulich@...ell.com>
> 
>  arch/i386/boot/video.S |   28 ++++++++++++++++++----------
>  1 files changed, 18 insertions(+), 10 deletions(-)
> 
> --- linux-2.6.22-rc5/arch/i386/boot/video.S	2007-04-26 05:08:32.000000000 +0200
> +++ 2.6.22-rc5-edid-no-vesa-mode/arch/i386/boot/video.S	2007-06-19 14:34:50.000000000 +0200
> @@ -96,6 +96,7 @@
>  #define PARAM_LFB_PAGES		0x32
>  #define PARAM_VESA_ATTRIB	0x34
>  #define PARAM_CAPABILITIES	0x36
> +#define PARAM_EDID_INFO		0x140
>  
>  /* Define DO_STORE according to CONFIG_VIDEO_RETAIN */
>  #ifdef CONFIG_VIDEO_RETAIN
> @@ -132,8 +133,8 @@ vid1:
>  #ifdef CONFIG_VIDEO_RETAIN
>  	call	restore_screen			# Restore screen contents
>  #endif /* CONFIG_VIDEO_RETAIN */
> -	call	store_edid
>  #endif /* CONFIG_VIDEO_SELECT */
> +	call	store_edid
>  	call	mode_params			# Store mode parameters
>  	popw	%ds				# Restore original DS
>  	ret
> @@ -571,16 +572,12 @@ 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
> @@ -1935,6 +1932,7 @@ skip10:	movb	%ah, %al
>  	popw	%cx
>  	popw	%ax
>  	ret
> +#endif /* CONFIG_VIDEO_SELECT */
>  
>  store_edid:
>  #ifdef CONFIG_FIRMWARE_EDID
> @@ -1945,18 +1943,28 @@ store_edid:
>  	pushw	%dx
>  	pushw   %di
>  
> +	pushw	%ds
> +	popw    %es
> +	leaw	modelist, %di
> +	movw	$0x4f00, %ax
> +	int	$0x10
> +	cmpw	$0x004f, %ax
> +	setne	%dl
> +	cmpw	$0x0200, 4(%di)			# only do EDID on >= VBE2.0
> +	adc	%dl, %dl
> +
>  	pushw	%fs
>  	popw    %es
>  
>  	movl	$0x13131313, %eax		# memset block with 0x13
>  	movw    $32, %cx
> -	movw	$0x140, %di
> +	movw	$PARAM_EDID_INFO, %di
>  	cld
>  	rep
>  	stosl
>  
> -	cmpw	$0x0200, vbe_version		# only do EDID on >= VBE2.0
> -	jl	no_edid
> +	testb	%dl, %dl
> +	jnz	no_edid
>  
>  	pushw   %es				# save ES
>  	xorw    %di, %di                        # Report Capability
> @@ -1978,7 +1986,7 @@ store_edid:
>  	movw	$0x01, %bx
>  	movw	$0x00, %cx
>  	movw    $0x00, %dx
> -	movw	$0x140, %di
> +	movw	$PARAM_EDID_INFO, %di
>  	int	$0x10
>  
>  no_edid:
> @@ -1991,6 +1999,7 @@ no_edid:
>  #endif
>  	ret
>  
> +#ifdef CONFIG_VIDEO_SELECT
>  # VIDEO_SELECT-only variables
>  mt_end:		.word	0	# End of video mode table if built
>  edit_buf:	.space	6	# Line editor buffer
> @@ -2000,7 +2009,6 @@ do_restore:	.byte	0	# Screen contents al
>  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, "
> 
> 
> 
> -
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