• Laptops
• HP_15-bw0xx

HP 15-bw0xx

• Year introduced: 2017

Hardware

bsd-hardware probes

1b5a45541a

Support overview

Tweaks

Brightness action keys

Upon a fresh install, the brightness action keys (Fn+F2,F3) do not work, but they can be configured:

1. Use kldstat to make sure the acpi_video driver is loaded. If it is not, append it to the list of modules to load via sysrc:

   • sysrc kld_list+=" acpi_video"

   Then reboot for the change to take effect, or load the driver manually:

   • kldload acpi_video

2. Prss Fn+F2 and Fn+F3 while reading devd.pipe to see which ACPI events are generated:

   • cat /var/run/devd.pipe

   You will see entries like these:

   !system=ACPI subsystem=Video type=brightness notify=49
   !system=ACPI subsystem=Video type=brightness notify=50

   where the notify value varies in the range 0..100 and is changed in unity steps for each key press. The value is stored in the sysctl variable hw.acpi.video.lcd0.brightness (assuming your main display), but it actual brightness remains the same. The backlight utility, however, works.

3. Since changing the brightness is such small unity steps is tedious, we can use backlight to change it be exponential steps, and rely on the dysfunctional sysctl variable to determine whether to increase or decrease action key was pressed. To do that, write the following script:

   REF=50 # an (arbitrary) reference value
   NEW=$1 # the new brightness value as received 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)

   and save it in a file with the execute permission, e.g. as /usr/bin/acpi_bri.sh.

4. Create the following devd rule:

   notify 10
   {       match  "system"    "ACPI"            ;
           match  "subsystem" "Video"           ;
           match  "type"      "brightness"      ;
           action "/usr/bin/acpi_bri.sh $notify";  };

   and save it in a .conf file under: /usr/local/etc/devd/.

5. Restart devd to activate the new rule:
   service devd restart

Files

CategoryLaptop