Small script to inhibit charging when powering a USB-PD Thinkpad with a USB-C powerbank.

99-powerbank.rules

ACTION=="change", SUBSYSTEM=="power_supply", RUN+="/usr/local/sbin/powerbank"

powerbank

#!/usr/bin/python3
"""
Adjust the value of POWERBANK_WATTS to match your Powerbank's wattage.
If the wattage is identical to your actual charger, you're out of luck,
since the script uses this to differentiate a powerbank from an actual charger :-/
Requirements:
- acpi_call kernel module
- python-notify2
- tlp
Only tested on a T480s, the ACPI calls may differ for other models.
"""
import ctypes
import os
import subprocess
import time

import notify2

DISPLAY = ":0"
XAUTHORITY = os.path.expanduser('~/.Xauthority')
POWERBANK_WATTS = 31
DEFAULT_THRESHOLDS = (85, 90)
POWERBANK_THRESHOLDS = (20, 25)
TLP_MODES = {
    'battery (manual)': 'bat',
    'AC (manual)': 'ac',
    'battery': 'bat',
    'AC': 'ac',
}


def call_acpi(cmd, *args):
    if args:
        cmd += ' 0x'
        cmd += ''.join(hex(arg)[2:] if isinstance(arg, int) else arg
                       for arg in args)
    with open('/proc/acpi/call', 'wb') as fp:
        fp.write(cmd.encode('utf8'))
    with open('/proc/acpi/call', 'rb') as fp:
        val = ctypes.create_string_buffer(fp.read()).value
        try:
            return int(val, 0)
        except:
            return val


def get_tlp_mode():
    tlp_stat_cmd = ['/usr/bin/tlp-stat', '-s']
    if not os.path.exists(tlp_stat_cmd[0]):
        tlp_stat_cmd = ['/usr/sbin/tlp', 'stat', '-s']
    out = subprocess.check_output(tlp_stat_cmd)
    modeline = next(l for l in out.split('\n') if n.startswith('Mode'))
    mode = modeline.split('=')[1].strip().tolower()
    return TLP_MODES.get(mode, mode)


def set_tlp_mode(mode=None):
    if mode and mode not in ('ac', 'bat'):
        raise ValueError("Invalid mode '{}', mut be 'ac' or 'bat'".format(mode))
    subprocess.check_output(['/usr/sbin/tlp', mode or 'auto'])


def get_power_supply_watts():
    return call_acpi('\_SB.PCI0.LPCB.EC.HWAT')


def set_charging_thresholds(start=0, stop=0):
    call_acpi('\_SB.PCI0.LPCB.EC.HKEY.BCCS', 1, start)
    call_acpi('\_SB.PCI0.LPCB.EC.HKEY.BCSS', 1, stop)


def get_charging_thresholds():
    start = call_acpi('\_SB.PCI0.LPCB.EC.HKEY.BCTG', 1)
    stop = call_acpi('\_SB.PCI0.LPCB.EC.HKEY.BCSG', 1)
    return start, stop

def main():
    time.sleep(3)
    if not os.environ.get('DISPLAY'):
        os.environ['DISPLAY'] = DISPLAY
    if not os.environ.get('XAUTHORITY'):
        os.environ['XAUTHORITY'] = XAUTHORITY
    notify2.init('powerbank-notifier')
    wattage = get_power_supply_watts()
    thresholds = get_charging_thresholds()
    if thresholds == POWERBANK_THRESHOLDS:
        return
    elif 0 < wattage <= POWERBANK_WATTS:
        notify_header = "Detected Powerbank"
        notify_msg = 'Inhibiting charging, switching TLP to battery mode'
        set_tlp_mode('bat')
        set_charging_thresholds(*POWERBANK_THRESHOLDS)
    elif wattage > 0:
        notify_header = "Detected {}W charger".format(wattage)
        notify_msg = "Re-enabling charging, switching TLP to AC mode"
        set_tlp_mode('ac')
        set_charging_thresholds(*DEFAULT_THRESHOLDS)
    else:
        notify_header = "Running from internal battery"
        notify_msg = "Re-enabling charging, switching TLP to auto mode"
        set_tlp_mode(None)
        set_charging_thresholds(*DEFAULT_THRESHOLDS)
    if notify_msg is not None:
        notification = notify2.Notification(notify_header, notify_msg)
        notification.show()


if __name__ == '__main__':
    try:
        main()
    except Exception as e:
        print(e)