Re: Hotplug events for system suspend/resume

[Pavel Machek <pavel@ucw.cz>]

Hi!

> >I still do not see the need for this.  As a user, you caused the
> >suspend/resume event to happen, why get notified of it again?  :)
> 
> The idea is to notify the "power management application" of impending 
> suspend and just-completed resume, regardless of who or what asked for 
> the suspend.  Actions taken at suspend might include dropping network 
> connections and saving application state to stable storage.
> 
> The reasons for which this was requested of me as a kernel-to-userspace 
> notifier, that I am aware of, are:
> 
> (a) some embedded platforms currently trigger suspend within kernel 
> drivers (in response to a button press or some sort of device
>timeout).

I believe kernel should userspace "button was pressed", and let
userspace ask it for suspend.

> (b) the system designer wants to make sure certain actions are always 
> taken regardless of the interface used to suspend (not only in the case 
> of a certain application that incorporates these actions and triggers 
> the suspend via the standard interfaces at the appropriate time).  For 
> example, a user manually enters a command from a shell prompt.

User should not manually do "echo something > /proc/acpi/sleep". For
embedded platforms, it should be rather easy to ensure user does not
do that, right?

OTOH, it might make sense to define that /etc/rc.d/suspend/* has to be
run before suspend and /etc/rc.d/resume/* has to be run after suspend;
by whoever who does suspend.

suspend-vetoing is pretty bad idea if your battery is running down. I
believe shutdown does it right: kill -15 -1; sleep 1; kill -9
-1. I.e. let apps know one second before suspend, but do not let them
veto it.
								Pavel
-- 
When do you have heart between your knees?


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