Wakelocks

Posted Dec 23, 2011 23:14 UTC (Fri) by dlang (guest, #313)
In reply to: Wakelocks by mjg59
Parent article: Bringing Android closer to the mainline

the problem is that userspace wakelocks don't solve the problem you are presenting either.

at least not unless every app can take them, but that's not what happens in android, only 'trusted' apps are allowed to take the wakelock.

in android they still use timeouts for most of userspace consuming events, and sidestep a huge amount of it by having the power controller have a wakelock for the entire time the screen backlight is on so that you don't have to scatter wakelocks through every app.

there are many of us who think that there are better ways of dealing with this userspace problem, but the problems of doing our own kernels makes it hard to experiment.

Wakelocks

Posted Dec 23, 2011 23:25 UTC (Fri) by neilbrown (subscriber, #359) [Link] (4 responses)

I don't quite follow - what exactly is the barrier that you see to experimentation?

Wakelocks

Posted Dec 24, 2011 6:20 UTC (Sat) by dlang (guest, #313) [Link] (3 responses)

the fact that I can't easily use the features that are in a kernel.org kernel with android userspace is one big barrier.

even if I am trying to compile my own android kernel, there doesn't seem to be any way of installing it on a device in a way that will let me fall back to the older kernel if I run into problems with the new one (the equivalent to the old lilo -R option)

the integration of things into the mainline will greatly help the first problem, but I still don't know a good solution for the second one.

Wakelocks

Posted Dec 24, 2011 11:50 UTC (Sat) by mjg59 (subscriber, #23239) [Link]

If you hit problems you just drop back to recovery and flash the old kernel back. Alternatively, do your testing using fastboot to push the kernel and ramdisk over USB and don't touch your flash at all.

Wakelocks

Posted Dec 24, 2011 12:30 UTC (Sat) by Cyberax (✭ supporter ✭, #52523) [Link]

You can use kexec, but I don't bother. On Galaxy S phones it's always possible to drop into "download mode" and just restore the old kernel image.

It's _always_ possible even if your firmware is totally corrupted and even battery controller is dead. In some cases it requires a magic jig, though (a 101kOhm resistor shorting two USB lines).

Wakelocks

Posted Mar 19, 2012 14:14 UTC (Mon) by jimmyflip (guest, #83547) [Link]

It's hard to imagine anyone doing even a small amount of Android kernel development wouldn't use 'fastboot boot' to test their kernel (assuming they have a capable bootloader). Any problems, just reboot.