> The proposal I made a couple of days ago removes this API and leaves > the other things (i.e., the in-kernel suspend blockers and > opportunistic suspend) intact. In place of the userspace > kernel-blocker API, Android would have to implement a power manager > process that would essentially juggle all the latency requirements in > userspace. On the kernel side you really want to add two arguments from day one which is the time in ms and the power state. We have enumerations of current power states (plus add suspend) so this is easy to do. The governors may not use them for a while but ACPI for example can use the latency pretty fast. You want the information there from day one so it is captured otherwise it ends up a right royal pain in the arse adjusting the API later. If the numbers are in but don't always get used it'll be a lot smoother. > Communication between the power manager process and the kernel would be > limited to adding a new "opportunistic" entry to /sys/power/state -- > something which could well be useful in its own right. Even if this > API turns out not to be good, it's simple enough that it could be > removed pretty easily. Yes. Probably it really should be linked to a cpufreq driver thing - cpufreq_android or whatever being the starting point but thats not a big deal and it doesn't leak into all the apps either. This is detail however. > Indeed, having a power manager thread may well turn out to be a useful > thing -- but even if it doesn't, this scheme minimizes the damage while > still allowing the Android platform to use a vanilla kernel with only > limited modifications to their userspace. There have been some horribly bad attempts to do this, but if it works for Android and its encapsulated in cpufreq_android.c maybe with a private interface to a single supporting daemon then it's not creating bad user APIs, its not peeing in anyone elses pond and the policy will all be in the kernel and a daemon which keeps the wrong platform knowledge out of the application space. Alan _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
