linux-kernel - Re : Re : Re : [HELP] Power management for embedded system

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Message-ID: <20060825133925.47842.qmail@web25810.mail.ukl.yahoo.com>
Date:	Fri, 25 Aug 2006 13:39:25 +0000 (GMT)
From:	moreau francis <francis_moreau2000@...oo.fr>
To:	Russell King <rmk+lkml@....linux.org.uk>
Cc:	linux-pm@...ts.osdl.org, linux-kernel@...r.kernel.org
Subject: Re : Re : Re : [HELP] Power management for embedded system

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 ?

>> Could you point out where it is handled ?
> 
> It's both machine class and CPU specific.  I couldn't point you at
> anything specific, except to say that different machines and ARM CPUs
> handle it differently.
> 
> Some CPUs have "wait for interrupt" instructions, some don't.  Some
> need special cache handling around this instruction, some don't.  Some
> machines have a CPU capable of "wait for interrupt" but must not use it.
> 
> It's all handled by the CPU abstraction, and the machine class abstraction.
> 
> See arch_idle in include/asm-arm/arch-*/system.h as the starting point
> for the "default" (== always used) idle implementations.
> 

thanks for that.

Francis



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