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.
Pavel is a long-term kernel hacker. He worked on amd64 kernel port and hibernation for SuSE. Currently he's co-maintaining hibernation and LED subsystem, and works with Denx on various embedded projects.
