linux-kernel - Re: [PATCH 16/18] 2.6.40: x86 idle APM: remove deprecated apm_cpu

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Message-ID: <20110402220021.74ecdb5b@lxorguk.ukuu.org.uk>
Date:	Sat, 2 Apr 2011 22:00:21 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Len Brown <lenb@...nel.org>
Cc:	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 16/18] 2.6.40: x86 idle APM: remove deprecated
 apm_cpu_idle()

> This patch series was posted in reply to a table of contents
> 
> https://lkml.org/lkml/2011/4/2/8
> 
> "By the end of this series, pm_idle is removed as a public
>  x86 idle-loop registration mechanism.  A few other things are
>  cleaned up in the process."

Ok so lets rewind a bit - why do we want to remove pm_idle rather than
just fix up the way registration occurs. It's just a symbol, one trivial
interface that is exported and perhaps wants the export method tidying up.

> Trinabh also replied to you, pointing one of the previous
> LKML discussions about the mis-use of pm_idle.

And there are misuses of just about every kernel symbol - kmalloc for
example causes some people a lot of trouble !

> We'll create a new APM cpuidle driver in Linux (Trinabh prototyped one),
> and at the same time, schedule it for removal in a year.  Personally,
> I think it is make-work, and in real-life it is more likely to do
> more harm than removing apm_idle, but I don't want to stand in the
> way of process.

So you could just leave it alone - that's less work, less disruption and
doesn't do any harm at all.

As I read this the plan at the moment otherwise is

	- churn up all the code
	- remove PM idle hook
	- rewrite the APM code
	- replace the APM code

whereas you could just leave the symbol exported or even just a hook to
make people to do it right using:

	int register_pm_idle(function);

Simples yes ?

and then wait a year

For that matter instead of writing a new driver you could just stuff APM
into same hooks we have for virtualisation !

This whole patch series appears to be a giant piece of pointless makework.

Alan
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