Re: Hang after "BIOS data check successful" with DVI

[Dave Jones <davej@redhat.com>]

On Tue, Aug 17, 2004 at 09:51:55AM -0400, Zwane Mwaikambo wrote:
 > On Tue, 17 Aug 2004, Petr Vandrovec wrote:
 > 
 > > On 16 Aug 04 at 16:55, Shaun Jackman wrote:
 > > > When I have a DVI display plugged into my Matrox G550 video card the
 > > > boot process hangs at "BIOS data check successful". I am running Linux
 > > > kernel 2.6.6. This problem does not affect Linux kernel 2.4.26. If I
 > > > boot without the DVI display plugged in, I can plug it in after the
 > > > boot process and the display works.
 > >
 > > Try disabling CONFIG_VIDEO_SELECT and/or comment out call to store_edid
 > > in arch/i386/boot/video.S. Also which bootloader you use? From
 > > quick glance at bootloaders, grub1 seems to set %sp to 0x9000, while
 > > LILO to 0x0800. And I think that 2048 byte stack (plus something already
 > > allocated by loader) might be too small for DDC call, as MGA BIOS first
 > > creates EDID copy on stack...
 > 
 > Urgh, this bug is still around :(
 > 
 > http://bugme.osdl.org/show_bug.cgi?id=1458

sidenote: A number of the int 10h calls in arch/i386/boot/video.S either
don't check the return code, and blindly assume everything went ok,
or do the wrong thing with them.

Example..

# get video mem size
    leaw    modelist+1024, %di
    movw    $0x4f00, %ax
    int $0x10
    xorl    %eax, %eax
    movw    18(%di), %ax
    movl    %eax, %fs:(PARAM_LFB_SIZE)

Checking http://www.ctyme.com/intr/rb-0273.htm shows that on return
from the int 10h, we should check al==4f before doing anything with
the results. Instead we not only ignore the return code, but trash it 8-)

Same story with function 4f0a a few lines below.

I did have a patch to change this a looong time ago (early 2.5)
but I don't know what became of it. Even google doesn't seem to turn it
up, so its possible I never got around to posting it.

		Dave