edd = Bios Enhanced Disk Drive Services

[Hugo Vanwoerkom]

Hi,

Back in May I reported a problem using 'vga=791' with post 2.6.24 Debian
686 kernels: the kernel booted w/o framebuffer support.

I reported this as a bug:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=481063

Turns out as of Oct. 4th 2008 that problem has been identified as having
to do with edd, specifically Debian has CONFIG_EDD=m and *that* causes
the problem on my system: EP-8VTAI mobo, 1G memory, 2-seater with a
GeForce 6200 PCI + GeForce 6200 AGP.

The solution is to specify 'edd=off' on the kernel commandline.

The kernel's help text says for this option:

Say Y or M here if you want to enable BIOS Enhanced Disk Drive
Services real mode BIOS calls to determine which disk
BIOS tries boot from. This information is then exported via sysfs.

This option is experimental and is known to fail to boot on some
obscure configurations. Most disk controller BIOS vendors do
not yet implement this feature.

For an extra 15 points on this test: how does one figure out whether one
has one of those "obscure configurations" *before* trying 'edd=off'?

Hugo

[Adrian Levi]

Hi,
Back in May I reported a problem using 'vga=791' with post 2.6.24 Debian 686
kernels: the kernel booted w/o framebuffer support.
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=481063
Turns out as of Oct. 4th 2008 that problem has been identified as having to
do with edd, specifically Debian has CONFIG_EDD=m and *that* causes the

I'm having trouble understanding why framebuffer and the disc
subsystem are close enough in the kernel that enabling a framebuffer
mode causes edd to fail.

EDD was working on its own, and presumably framebuffer=791 works on its own?

Why is the interaction between these two things causing new problems?

Adrian
--
24x7x365 != 24x7x52 Stupid or bad maths?
<erno> hm. I've lost a machine.. literally _lost_. it responds to
ping, it works completely, I just can't figure out where in my
apartment it is.

[Hugo Vanwoerkom]

Post by Adrian Levi

Hi,
Back in May I reported a problem using 'vga=791' with post 2.6.24 Debian 686
kernels: the kernel booted w/o framebuffer support.
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=481063
Turns out as of Oct. 4th 2008 that problem has been identified as having to
do with edd, specifically Debian has CONFIG_EDD=m and *that* causes the

I'm having trouble understanding why framebuffer and the disc
subsystem are close enough in the kernel that enabling a framebuffer
mode causes edd to fail.
EDD was working on its own, and presumably framebuffer=791 works on its own?
Why is the interaction between these two things causing new problems?

I have no idea. But I found 2 descriptions of the problem:
http://www.gossamer-threads.com/lists/linux/kernel/974276
http://fixunix.com/kernel/548915-framebuffer-issues-2-6-26-uvesafb-vesafb-linux-about-choice.html

I verified by recompiling linux-image-2.6.26-1-686 with not setting
CONFIG_EDD that it does indeed solve the problem.

As you see from the bug description I owe the solution to Vedran Furač
who appended the bug report with the solution but did not specify how he
discovered that.

Googling vesafb + edd shows the solution but w/o edd it's like looking
for a needle in a haystack.

Hugo