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

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Message-Id: <20070708111404.1486e73c.akpm@linux-foundation.org>
Date:	Sun, 8 Jul 2007 11:14:04 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Daniel Drake <dsd@...too.org>
Cc:	Jan Beulich <jbeulich@...ell.com>, linux-kernel@...r.kernel.org,
	zwane@...radead.org, Andi Kleen <ak@...e.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Antonino A. Daplas" <adaplas@....net>
Subject: Re: [PATCH] retrieve VBE EDID/DDC info independent of used video
 mode

On Sun, 08 Jul 2007 09:27:55 -0400 Daniel Drake <dsd@...too.org> wrote:

> Andrew Morton wrote:
> > On Sat, 30 Jun 2007 18:25:31 -0400 Daniel Drake <dsd@...too.org> wrote:
> >> 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 :)
> > 
> > Well drat.  I didn't merge the patch because it conflicts with
> > git-newsetup, and Peter believes that git-newsetup already contains an
> > equivalent fix.  Testing 2.6.22-rc6-mm1 would confirm that.  Please.
> 
> 2.6.22-rc6-mm1 has the same problem (it is not fixed there).
> 

Well damn, we've let this slide for too long.

Guys, 2.6.22 is days away.  Do we think that the below is safe to merge
now?

Add Daniel, this does fix things for you, doesn't it?


From: "Jan Beulich" <jbeulich@...ell.com>

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.

Signed-off-by: Jan Beulich <jbeulich@...ell.com>
Cc: Daniel Drake <dsd@...too.org>
Cc: Andi Kleen <ak@...e.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: "Antonino A. Daplas" <adaplas@....net>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 arch/i386/boot/video.S |   28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff -puN arch/i386/boot/video.S~retrieve-vbe-edid-ddc-info-independent-of-used-video arch/i386/boot/video.S
--- a/arch/i386/boot/video.S~retrieve-vbe-edid-ddc-info-independent-of-used-video
+++ a/arch/i386/boot/video.S
@@ -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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