BIOS password...: probably on latitudes only

Mario_Limonciello at Mario_Limonciello at
Wed Jul 23 08:17:40 CDT 2008


It shouldn't cause hard resets, just freezes.  If you think for some reason this is the root cause however, just turn off the dimming feature in gnome power manager so that the brightness isn't attempted to be adjusted.


Mario Limonciello 
Dell | Linux Engineering 
Mario_Limonciello at 

-----Original Message-----
From: Lance Haig [mailto:lnhaig at]
Sent: Wed 7/23/2008 4:32 AM
To: Limonciello, Mario
Cc: linux-desktops
Subject: Re: BIOS password...: probably on latitudes only
Hi Mario,

Do you think this problem would cause a machine to hard reset and restart?

I am trying to find out why if I start a vm with qemu-kvm it resets the 



Mario Limonciello wrote:
> Andrea:
> I've uploaded 4 fixes that were all attached to that bug that are being
> processed right now.  If you (and anyone else that has encountered this
> problem) could follow the directions on
> to update to the newer libsmbios and HAL packages and then comment on
> that bug, that would be most appreciated.  After some positive feedback
> is received with the new packages, they can be pushed to all machines.
> A little background about the solution:
> The current method of changing the backlight uses a BIOS call to
> actually perform this backlight change on Linux.  On Windows, this
> function isn't stubbed out at all per my understanding.  The ambient
> light sensors of the laptop may be activated in Windows, but any
> adjustments to the backlight are either done physically by pressing the
> up and down buttons for the backlight or by the BIOS without interaction
> with Windows.  On the Linux side, since these functions actually got
> stubbed out, there is software support for changing the backlight.  The
> BIOS can not be written to however, unless an authentication token is
> obtained.  This token gets obtained by providing a user or admin BIOS
> password.
> What I did was provided another method to libsmbios that queries
> directly if there is a type of password present.  I then added a check
> to HAL to see if there is a BIOS password.  If there is, any attempts to
> write to the backlight will not actually make the call into libsmbios,
> but just return.  This will prevent the "lockups" that were encountered
> when multiple calls to change the backlight were happening w/o valid
> tokens.  Those were caused because making a query to change the BIOS
> multiple times appeared to invoke an interrupt handler.
> All in all, the negative side effect to this solution will be the fact
> that any software utilities that would change the backlight won't work
> when you have a BIOS password set.  They didn't work before either
> though, so I don't see this as a regression.
> Regards,
> Andrea Ratto wrote:
>> probably happens on latitudes (d series?) only...
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