Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

[Arve Hjønnevåg]

On Thu, May 27, 2010 at 3:23 PM, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> wrote:
> On Thu, 27 May 2010 23:09:49 +0100
> Matthew Garrett <mjg59@xxxxxxxxxxxxx> wrote:
>
>> On Thu, May 27, 2010 at 11:08:06PM +0100, Alan Cox wrote:
>>
>> > This is I believe robust (and has been implemented on some non x86
>> > boxes). It depends on not forcing running tasks into suspend. That is the
>> > key.
>>
>> We've already established that ACPI systems require us to force running
>> tasks into suspend. How do we avoid the race in that situation?
>
> Android phones do not have ACPI. Embedded platforms do not have ACPI. MID
> x86 devices do not have ACPI.
>

Android does not only run on phones. It is possible that no android
devices have ACPI, but I don't know that for a fact. What I do know is
that people want to run Android on x86 hardware and supporting suspend
could be very benficial.

> I would imagine the existing laptops will handle power management limited
> by the functionality they have available. Just like any other piece of
> hardware.

I think existing laptops (and desktops) can benefit from opportunistic
suspend support. If opportunistic suspend is used for auto-sleep after
inactivity instead of forced suspend, the user space suspend blocker
api will allow an application to delay this auto sleep until for
instance a download completes. This part could also be done with a
user-space IPC call, but having a standard kernel interface for it may
make it more common. A less common case, but more critical, is RTC
alarms. I know my desktops can wakeup at a specific time by
programming an RTC alarm, but without suspend blockers how do you
ensure that the system does not suspend right after the alarm
triggered? I have a system that wakes up at specific times requested
by my DVR application, but I cannot use this system for anything else
unless I manually turn off the DVR application's auto-sleep feature.
With suspend blockers and something like the android alarm driver, I
could use this system for more than one application that have
scheduled tasks and it would be more usable for interactive
applications.

-- 
Arve Hjønnevåg
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