Question

I am trying to get the battery level inside a Linux kernel module (the module is inserted via modprobe). I would ideally like to use a kernel API call to get the battery information. I have searched on the web for solutions, and I have also explored Linux kernel source and the source of program "acpi" by Michael Meskes for ideas.

These are some of the techniques I think I can use:

Read and parse /proc/acpi/battery/BAT0/state and /proc/acpi/battery/BAT0/info
Read from /sys/class/power_supply/BAT0/charge_now and charge_full with no parsing involved.
I could try using the calls from Linux kernel source drivers/acpi/battery.c if I could figure out how to expose the interface. I would probably need the methods acpi_battery_get_status and acpi_battery_get_info
I also noticed that inside drivers/acpi/sbs.c there s a method acpi_battery_read and right above it there is a comment saying "Driver Interface". This might be another way if anyone knows how to use this.

I assume that it is probably a bad idea to read files while inside a kernel module, but I am not exactly sure how those files map to kernel function calls, so it might be okay.

So, can you guys give me some suggestions/recommendations?

Edit: I included my solution in an answer below.

Answer 1

I have found a solution that works for me. First of all make sure to #include < linux/power_supply.h >

Assuming you know the name of the battery, this code gives an example of how to get current battery capacity.

char name[]= "BAT0";
int result = 0;
struct power_supply *psy = power_supply_get_by_name(name);
union power_supply_propval chargenow, chargefull;
result = psy->get_property(psy,POWER_SUPPLY_PROP_CHARGE_NOW,&chargenow);
if(!result) {
    printk(KERN_INFO "The charge level is %d
",chargenow.intval);
}
result = psy->get_property(psy,POWER_SUPPLY_PROP_CHARGE_FULL,&chargefull);
if(!result) {
    printk(KERN_INFO "The charge level is %d
",chargefull.intval);
}

Answer 2

Looking at the battery.c, sbs.c, I think you can call the interface API (acpi_battery_read, acpi_battery_get_state) in your LKM directly.
Did you try that so far?

Answer 3

I have the same dilemma! :- If this is a hardware specific thing you r doing, you could see if on your particular laptop you can detect the smart battery on the SMBus link or not. If you can, then you can just do i2c/SMBus calls from within your LKM. Most new systems (except some Fujitsu laptops) talk to an embedded controller instead, which ends up configuring the battery (through SMBus i suppose).... Try installing "lm-sensors" and see if it detects your smart battery. If so you should be able to talk directly to the battery (usually at i2c address 0xb).

If this isn t a hardware specific thing you re doing, then ignore what i said :)

友情链接