This is an ugly-ass hack to temporarily fix a brightness jumping problem with some nvidia-based laptops on Linux, until nvidiabl/nvidia drivers fix the issue. Watches the actual brightness of the display, and when it jumps up past the maximum, resets it to the original desired value.

nvidia_brightness_watcher.py

#!/usr/bin/env python

import os
import time

BACKLIGHT = 'nvidia_backlight'
DELAY = 0.2

def get_value(name):
    path = os.path.join('/sys/class/backlight', BACKLIGHT, name)
    return int(open(path, 'r').read())

def set_value(name, value):
    path = os.path.join('/sys/class/backlight', BACKLIGHT, name)
    open(path, 'w').write(str(value))

def watch_brightness():
    maximum = get_value('max_brightness')
    while True:
        actual = get_value('actual_brightness')
        if actual > maximum:
            desired = get_value('brightness')
            set_value('brightness', desired)
        time.sleep(DELAY)

if __name__ == '__main__':
    watch_brightness()

See discussion here: guillaumezin/nvidiabl#56