On Mon, 31 May 2010 08:43:56 +0200 Florian Mickler <florian@xxxxxxxxxxx> wrote: > On Mon, 31 May 2010 09:57:53 +1000 > Neil Brown <neilb@xxxxxxx> wrote: > > > 2/ Rather than tracking wake-events from the hardware up through possibly > > several kernel modules, you go directly from hardware to user-space so each > > event is potentially presented to user-space twice: once as a "wake up > > from low power state" event and once following the normal path (maybe a > > key-press event, maybe a serial-port event, maybe a network receive event). > > I can see that this is a very tempting approach. It allows all those > > intermediate modules to remain unchanged and that is good. > > However it isn't clear to me that this would be easy for user-space to use > > correctly. > > When an lpe event arrived it would need to wait around for the real event > > to arrive and then process that. I probably wouldn't wait long, but it > > would be an indeterminate wait, and it might not be trivial to determine > > if all events that would cause a wake-up have been consumed as a direct > > mapping from lpe event to normal event may not always be possible. > > Maybe this is more of a theoretical problem and in practice it would be > > easy to get it right - I don't have enough concrete experience to be sure. > > > > So: I like the idea of leaving the intermediate layers unchanged, but I'm > > not convinced it would work. > > To add to this: Is it a correct assumption > that all wake-up events that leave a driver trickle eventually up to > userspace? > > I think splitting the actual driver product (i.e. keypress or whatever) > of a wake-up-event and it's corresponding wake-lock is not possible. > Because you would have to _somehow_ map the block back to the product > when you consume the product. > > If you want to abstract the blocking from the kernel-code you probably > have to introduce an abstract "driver-product" entity where you can do > all your blocking associated with the product but hidden from the code > that uses the product. (Which I don't think is feasible, because it > increases overhead) > > Or am I on the wrong track here? I just realized, that you can cancel lpe_blocks via delete_lpe_block(), so this is not an issue at all. They can be used just like suspend blockers. Also the mapping of lpe_block to "wake event" is the same problem as with the suspend_blockers... So I don't think this is a bad idea after all. It decouples the suspend_blockers from "suspend" quite nicely. Although it still is only "block" or "no block" and not, as was suggested some sort of more fine grained requirement definition. Cheers, Flo _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
