Affected file:
sys/dev/acpica/acpi_cmbat.c
Short description:
You don't need to poll the battery periodically.
You can set a percentage level for your battery (ranging from 0-100) via sysctl.
If the level is reached, it will cause a /dev/devd event Notify(0x80). So a script can be triggered.
Long description: A New Battery Warning Level
The ACPI specification defines an optional acpi method called "_BTP", which stands for battery trip point.
However, currently the FreeBSD cmbat driver only supports mandatory methods (bif, bix, ..), but not optional ones.
Try the command: "acpidump -dt |grep _BTP".
If it returns something, your battery supports this method.
If supported by the battery, a new sysctl is created: dev.battery.X.Warning_Level
Replace the X with your battery index (0, 1, ...).
You can set the warning level ("trip point") with this sysctl (values between 0-100 are allowed).
If the battery reaches that percentage level, devd will be notified.
A value of 0 disables the warning.
Get the notification:
Next add an entry in /etc/devd.conf:
notify 10 {
match "system" "ACPI";
match "subsystem" "CMBAT";
action "/home/myuser/myscript.sh $notify";
};
Replace myuser with your local user. Replace myscript.sh with a script of your choice.
Note:
If the battery gets unplugged/plugged in, an identical notification will be issued (at least on my laptop).
So the script needs to take that into account.
Note:
There is a slight delay in the devd notification.
E.g. if you set the warning level to 20%, you may get notified at 19,5%. This is due to granularity.
Personal note:
If you have any questions, please write me. Then I will look at this again.
Tested on a thinkpad x220.
Thanks. :-)
Installation guide for beginners:
Step 1:
Try the command: "acpidump -dt |grep _BTP".
If it returns something, your battery supports this function.
Step 2:
Donwload the Freebsd source code.
Replace the file from this repo with the file /usr/src/sys/dev/acpica/acpi_cmbat.c
Step 3: Build and install the new kernel.
Step 4:
Add an entry in /etc/devd.conf:
notify 10 {
match "system" "ACPI";
match "subsystem" "CMBAT";
action "/home/myuser/myscript.sh $notify";
};
Step 5:
Replace mysuser and myscript with an actual user and an actual script.
Step 6:
Set the sysctl dev.battery.0.Warning_Level to your desired warning level. If it works, give me feedback.