Re: Need help controlling laptom display brightness via sysctl

Kevin Oberman:

> This is what I used. I have it in /etc/devd/thinkpad.conf.
>
> notify 100 {
>          match "system"                  "ACPI";
>          match "subsystem"               "IBM";
>          match "notify"                  "0x10";
>          action "/usr/bin/backlight +";
> };
>
> notify 100 {
>          match "system"                  "ACPI";
>          match "subsystem"               "IBM";
>          match "notify"                  "0x11";
>          action "/usr/bin/backlight -";
> };
>
> 10% changes are more reasonable than 1%. The top two
> "notify"s set the screen at 100% on AC and 40% on battery.

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.  See what I mean?