Re: apm screen blanking

Garst R. Reese (
Thu, 26 Feb 1998 14:47:21 -0400

C. Scott Ananian wrote:
Date: Wed, 25 Feb 1998 17:27:16 -0500 (EST)
Subject: apm screen blanking.

On Wed, 25 Feb 1998, Garst R. Reese wrote:

> In X the screen blanks after 8 min. This was the blank time I had my
> bios set to when I installed X, but I have since changed it to 2 min. On
> a non X VC it blanks and turns off the backlight in 2 min.
> XFree86 v3.2 linux-2.1.88 MidWestMicro Elite SoundBook DX2/66 mono.

I'm currently concentrating on finding the bug that causes notebooks to
hang on 'suspend to disk' in linux (but not NT/win95! [argh]), but I've
gotten several messages of this type. I've heard comments on the list
that 'X screen blanking is broken' -- can anyone explain this further?
Most apm bug reports say that non-X VCs are fine, so at this moment I'm
blaming this on XFree86.

Would performing a VESA power-off help, in addition to possibly faulty
screen blanking? [the current linux kernel does not do the VESA
if the APM screen-blanking reports success].

[snipped :)]

<useful request>
I'd appreciate if a number of notebook users with suspend-to-disk
could drop be a quick line. I'd like to a) compile a list of
known-problematic laptops to put in the documentation, and b) have a
of people to distribute debugging code or alpha patches to.
</useful request>
Garst replies:
Happy to try any patches.
I dl'd the apm docs. The two things I noticed were that 1) the device
numbers start at 0, and 2) that ff is in caps e.g. 0x01FF. This has
never made a difference anywhere else, but it IS and MS doc ;) so I
tried out 0x0100 and 0x01FF.
In both cases, the back light turns off, but with FF, I get the
Unrecognized device msg. Furthermore, after about 30 s. the screen
reactivates, then cycles on-off every 2 m or so. This acutually happend
with all of the other dumb codes I tried. I have 'Video Monitoring'
disabled which, according to my bios docs means that video RAM access
does not prevent the system from entering Standby or Suspend mode. With
everything except Ox0100 I get this in my logs:
Feb 26 12:56:01 grr kernel: apm_bios: set display standby: Unrecognized
device ID
Feb 26 12:56:01 grr kernel: apm_bios: set display ready: Unrecognized
device ID
Feb 26 13:06:05 grr kernel: apm_bios: set display standby: Unrecognized
device ID
Feb 26 13:06:06 grr kernel: apm_bios: set display ready: Unrecognized
device ID
It seems that something is triggering screen blanker to tell it to wake
up. This happens even if I do not have X started. My dumb guess is that
the problem is in console.c.
Have not tried suspend to disk, but plain suspend works if I eject
pcmcia cards first.


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