LED devices

[Richard Hughes]

More and more drivers are exporting LED devices using the kernel led
class framework.

In particular, soon the thinkpad_acpi driver will export the thinklight
over the led framework. I want to toggle this led in low ambient light
conditions from the session in gnome-power-manager. Other system and
session stuff will be wanting to control LED devices on embedded devices
(think OLPC) and so I think this trivial sysfs to hal device mapping
should be done in HAL in my opinion.

Should HAL control these devices? Adding them as devices in the HAL tree
is trivial, and we probably done want GetLedState and SetLedState(i)
methods on each one. We could even just use properties to convey state
which might be more efficient.

The led framework (as is) is pretty sparse on information, and we can't
really get many capabilities (if the light can flash, what colour the
light is) although I'm prepared to code the kernel changes if need be.

So, comments? suggestions? Thanks.

Richard.