[lkml]   [2007]   [Feb]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: Linus' laptop and Num lock status
On Wed, 2007-02-14 at 11:32 -0800, Linus Torvalds wrote:
> On Wed, 14 Feb 2007, Jean Delvare wrote:
> >
> > On x86, the BIOS led state can be read from byte 0x97 the BIOS RAM. The
> > BIOS RAM is mapped at 0x400 so all we need to do is to one byte from
> > RAM (offset 0x497). This is how Suse's hwinfo does.
> Heh. Shows just how much I ever used DOS and BIOS.
> > But maybe the first question to ask is: why is the BIOS setting lost in
> > the first place? Why is the kernel resetting the led state?
> Ehh. Silly question. "Those flags, they do nothing."
> The kernel needs to know what they are in order to react correctly to
> them. And since you can't read them from hardware, the only way to know
> what they are (if you don't know about BIOS magic areas) is to SET THEM.
> Which is what the kernel has traditionally always done.

Going forward can the kernel peek at 0x497 and follow the BIOS setting?

I checked, and looking at offset 0x497 seems to work fine on a couple of
systems with USB keyboards.

People have long grumbled and complained about the current kernel
behavior (1).

Dax Kelson


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2007-02-14 22:37    [W:0.165 / U:1.356 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site