Date: Sun, 7 Jul 2024 22:27:54 +0300 From: Anton Shepelev <anton.txt@gmail.com> To: freebsd-stable@freebsd.org Subject: Re: Need help controlling laptom display brightness via sysctl Message-ID: <20240707222754.2a531eb3344cb4644c571c66@gmail.com> References: <20240704010029.75608a4e49205eb38a6034be@gmail.com> <20240705005834.4c7983ea29da3af8f8e36718@gmail.com> <CAN6yY1uo%2Be6pY1H7JSyHKjjbB8O6a_UAoW=NoagzXSCc%2BHzaHQ@mail.gmail.com>
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I wrote to Kevin Oberman:
> I fear you missed my point that HP seems to have a
> different approach to these ACPI events. In ThinkPad, the
> up- and down-brighness events have fixed notify codes:
> 0x10 and 0x11. In HP, on the other hand, the notify codes
> represent the target brightness level on a 0..100 scale,
> so that consequtive presses of Fn+F3 yield an arithmetical
> progression of notify codes, e.g. 51,52,53 &c, which is
> why the simplest solution is to subsitute the notify value
> into the invocation of `backlight'.
>
> Translating those codes into exponential changes would
> require first of all to recall the previous value in order
> to determine whether the current event is an increase or a
> decrease.
Indeed, and here is my final devd action stript:
REF=50 # an (arbitrary) reference value
NEW=$1 # the new brightness value as recevied from ACPI
# Ignore the ref. value to avoid an infinite loop:
if [ $NEW -eq $REF ]; then exit 0; fi
# Determine whether to increase or decrease the brightness:
if [ $NEW -lt $REF ];
then OP=decr
else OP=incr; fi
# Change brightness:
backlight $OP
# Restore the reference value:
sysctl hw.acpi.video.lcd0.brightness=$REF
# (in this system it has no effect on the actual brightness)
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