On Tue, Oct 24, 2023 at 09:32:24AM +0200, basti wrote: > > > On 24.10.23 06:18, David Wright wrote: > > On Mon 23 Oct 2023 at 20:03:50 (+0200), basti wrote: > > > I have a Lenovo E16 Gen1 with Intel Iris and try to adjust brightness > > > via Fn-Keys. > > > All other Fn-Keys are working.
[...]
> OK, I can write the values to
> /sys/class/backlight/intel_backlight/brightness
>
> The default is 15040, which seems to be the maximum.
> Nothing visible changes between 15040 and 13000.
> 60 is very dark.
> It therefore looks like an exponential function.
>
> I have to see how I can represent this in a function to use it with the
> fn-keys.
What I have done (Thinkpad X230 here) is to put this in
/etc/acpi/actions/brite (call it how you like):
========================================================================
#!/bin/sh
logger "[ACPI] $@"
BASE="/sys/class/backlight/intel_backlight"
CURR=$(cat "$BASE/brightness")
MAX=$(cat "$BASE/max_brightness")
# MIN is some arbitrary "low" value. Note that for values
# of MIN below 6 (more precisely: 2/11 for our factor), the
# thing gets stuck at the low end: (13 * x) / 11 == x,
# in integer arithmetic, for x <= 5.
#
# The "exponential" algorithm is a bit long at the low
# end. We might consider stretching there. Or increasing
# MIN.
MIN=20
if [ "$CURR" -lt "$MIN" ] ; then CURR="$MIN" ; fi
# NOTE: 11/13 is approx the fourth root of 1/2:
# i.e. four steps are a doubling/halving
# of brightness (constant steps gave too
# coarse jumps in the low range)
case $1 in
video/brightnessdown* )
NEW=$(( (11 * CURR) / 13 ))
;;
video/brightnessup* )
NEW=$(( (13 * CURR) / 11 ))
;;
* )
exit 0
;;
esac
if [ "$NEW" -lt "$MIN" ] ; then NEW="$MIN" ; fi
if [ "$NEW" -gt "$MAX" ] ; then NEW="$MAX" ; fi
logger "[ACPI] brightness $CURR --> $NEW"
echo "$NEW" > $BASE/brightness
========================================================================
The real action is in the last line, which writes to the sys file.
Then hook it up on your acpi events. In /etc/acpi/events/briteup , I
have this:
========================================================================
event=video/brightnessup
action=/etc/acpi/actions/brite "%e"
========================================================================
and in .../britedn, this
========================================================================
event=video/brightnessdown
action=/etc/acpi/actions/brite "%e"
========================================================================
I *think* that was all. Now you have to find out how the ACPI events
are actually spelt by your computer (the "brightnessup" and "...down"
above). For this, you enter
acpi_listen
into your favourite terminal and hit the keys in question.
It's a long while ago and my notes are fragmentary, so perhaps I've
forgotten something.
The nice part is that this works outside of X, too.
Cheers
--
t
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