On Fri, Aug 25, 2006 at 01:39:25PM +0000, moreau francis wrote:
> Russell King wrote:
> > We have some folk who want a method to trigger emergency suspends when
> > batteries got low, or if you move the battery cover, etc. These are
> > events which require fast reactions from the system, and coding up some
> > additional interface to pass such events to userland, have some daemon
> > running to monitor for those events, and issue a PM event is completely
> > overkill and, actually, unreliable.
> >
>
> I'm not sure to understand why a daemon is needed. Could you explain ?
Consider how you would make a connection between an interrupt being
triggered and a suspend occuring, bearing in mind that you require
a process context to perform a suspend.
You essentially have three options:
1. a kernel thread, to which you pass an event or trigger condition.
2. a userland daemon which waits for the interrupt via some special
kernel interface and triggers a suspend via normal userspace
channels.
3. some hotplug-triggered userspace method.
Note that both 2 and 3 have the same limitation - since they use normal
userspace channels which have no concept of "emergency suspend", it's
quite possible for (eg) a busy X server to inappropriately delay such a
suspend.
Therefore, I chose (1) as being the most appropriate solution.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
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