Re: wsdisplay brightness issue on amd64

On Sun, Aug 09, 2026 at 11:12:56AM +0100, Jason McIntyre wrote:
> hi/
> 
> when this machine boots, the screen display dims severely right about the
> time my wsdisplay attach shows in dmesg. i can fix it manually by
> adjusting display.brightness.
> 
> setting display.brightness to 0 is brighter than the booted default.
> 
> setting most display.brightness values work as normal, but 97-100 revert
> it to this super dim state.
> 
> i have not updated the laptop in two weeks, so hard to pin down when
> this would have happened (it's running current).
> 
> i confirmed this happened on a boot of stock /bsd.mp.
> 
> can;t think of anything else!
> jmc
> 

a little progress:

firstly i mis-diagnosed the issue. display.brightness=0 is not brighter
than the booted default! i'm not exactly sure how i reached that
conclusion.

but what i do see is values 97-100 severly dimming the screen. that
suggests a weird round up/bounds check (heh, i'm winging it here). i
noticed because i normally set max brightness in wsconsctl.conf, so it
dimmed my screen.

i narrowed it down to a commit between

	Sun Aug 2 23:29:09 MDT 2026
and
	Mon Aug 3 22:42:09 MDT 2026

(thanks nick for the archive reminder)

commits on those dates suggest the updates to drm. there are a lot, and
i'm blind. i'm ccing jsg in case he sees something obvious.

jmc