This week's episode of "Desperate Androids"

The API for a driver to say "I've started something that needs to finish before the system can be considered idle enough to suspend" and "This thing is done now" should be pretty obvious. Even if some sort of QoS thing turns to be the real API, the above is still going to be a common enough case to justify having a helper rather than making everybody open-code the necessary QoS-setting call.

Of course, if the kernel lacks a mode where the system suspends because it is idle, the implementation is uncontentious: the kernel doesn't need to do anything when drivers call those functions. So Android drivers would be able to act to keep the kernel from autosuspending at a bad time, because a mainline kernel doesn't autosuspend ever and a kernel with autosuspension does something real with those functions.