On Mon, 31 May 2010 09:57:53 +1000 Neil Brown <neilb@xxxxxxx> wrote: > On Sun, 30 May 2010 13:04:10 -0700 > mark gross <640e9920@xxxxxxxxx> wrote: > > > Low Power Events is a possible alternative to suspend blocker / wake > > lock API used by Android. > > Here is how I see your proposal. It is of course possible that I > misunderstood bits, so please correct me where I'm wrong. > > 1/ You have introduced a new mechanism for requesting a transition > to a low power state. This involves writing a number to /dev/lpe_enter. > It is not clear to me from your text what the magic number really means. > I think this parallels writing to /sys/power/state, but achieves the same > result though a different mechanism and adds some extra checking. > So: I don't understand the numbers, and I don't see why we need a > second way to request a low power state. Probably I missed something > important. I can only think for lpe to provide the levels and have userspace and platform code hook into there. Else you would have a dependency from userspace to platform code. > > 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? cheers, Flo _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
