January 27, 2020

219 words 2 mins read

LED Subystem in Kernel

LED Subystem in Kernel

LEDs are very simple, cheap and common devices, and we have easy-to-use subsystem to handle them. Few lines in device tree are enough to drive simple LED. Unfortunately, there's little standartization …

Talk Title LED Subystem in Kernel
Speakers Pavel Machek (kernel hacker, Denx)
Conference Open Source Summit + ELC Europe
Conf Tag
Location Lyon, France
Date Oct 27-Nov 1, 2019
URL Talk Page
Slides Talk Slides
Video

LEDs are very simple, cheap and common devices, and we have easy-to-use subsystem to handle them. Few lines in device tree are enough to drive simple LED. Unfortunately, there’s little standartization going on, and there are great differences between devices, so supporting LEDs is not easy: some LEDs can be accessed from interrupts (and we want to use that capability), some take 300msec to update. Most are on/off, but PWM is getting common, and so are three LEDs in one package, allowing display of RGB color. LED subsystem currently treats RGB LED as three separate LEDs, which is not optimal. Then there are triggers, such as “CPU activity”, and we have sysfs interface for them. But newer hardware tends to have “this LED is either software controlled or shows ethernet link”, and we want good interface for that. Other open issue is LED device naming; currently names are not very consistent.

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