How to power gate a specific single device from outside?

[Waldemar Rymarkiewicz]

Hi

I am looking for a convenient way to power gate specific single device
when the platform is running in backup mode - the platform lost main
power supply and it's on backup buttery now. The intention is to save
max power in backup mode and switch off all unnecessary blocks.

I could not find anything standard that let me power gate single
device from userland. Perhaps it's considered as a too risky operation
to expose to the user. I don't want to touch drivers too much as well
not to make them dependant on extra system feature. Better to have a
separate module that handles this system mode and forces some drivers
to unload/power gate their HW.

Are there already some proven solutions/ideas around the kernel that
can be used straight away?

Suggestions appreciated.

/Waldek