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Where is the LCD brightness stored?

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kpedersen_
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Joined: Thu Aug 09, 2018 9:56 am
Location: Bournemouth, UK

Where is the LCD brightness stored?

#1 Post by kpedersen_ » Thu Aug 09, 2018 10:03 am

Hi all,

In the past, on my x61, my default startup brightness could be set by going into the BIOS and using the brightness up key. From then on it would be permanently saved so that my OS (FreeBSD, Linux, etc) could set it in the rc.local and my eyes not be melted in the meantime.

With my X1 Carbon, it is on fully until the OS finally gets round to changing it in the rc.local. My eyes hurt especially if I start it up late at night haha.

Where are the defaults stored? I am guessing as one of them new fangled EFI variables. I think in Linux I can use the /sys/EFI/vars mechanism to change them but is there an equivalent for FreeBSD or OpenBSD?

Even better, can I set EFI variables without an OS, i.e like back in the good old days of an actual BIOS menu?

dr_st
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Re: Where is the LCD brightness stored?

#2 Post by dr_st » Thu Aug 09, 2018 3:32 pm

AFAIK, brightness being always on in the pre-boot environment is a design limitation of the new models, and there is no way to change it.
Thinkpad 25 (20K7), X1 Carbon (20HQ), Yoga 14 (20FY), T430s (IPS FHD + Classic Keyboard), X220 4291-4BG, X61 7673-V2V
T60 2007-QPG, T42 2373-F7G, X32 (IPS Screen), A31p w/ Ultrabay Numpad, A21m 2628-GXU

kpedersen_
Posts: 2
Joined: Thu Aug 09, 2018 9:56 am
Location: Bournemouth, UK

Re: Where is the LCD brightness stored?

#3 Post by kpedersen_ » Fri Aug 10, 2018 10:15 am

Oh right. Nice design.

The brightness of Windows does kick in slightly faster than /etc/rc.local but yes, it does still start in full brightness.

I assumed that the reason why my Windows was not storing the startup brightness in an EFI variable when changing brightness was because I didn't have the right drivers installed (and the same for Linux, BSD). I didn't realize there was a design flaw at play.

Oh well. Thanks a lot for your help :)

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