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

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Date:	Wed, 26 May 2010 14:54:52 +0200
From:	Florian Mickler <florian@...kler.org>
To:	felipe.balbi@...ia.com
Cc:	Vitaly Wool <vitalywool@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Paul@...p1.linux-foundation.org" <Paul@...p1.linux-foundation.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux PM <linux-pm@...ts.linux-foundation.org>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

On Wed, 26 May 2010 15:35:32 +0300
Felipe Balbi <felipe.balbi@...ia.com> wrote:

> Hi,
> 
> On Wed, May 26, 2010 at 02:33:23PM +0200, ext Florian Mickler wrote:
> >But then someone at the user side has to know what he is doing.
> >
> >I fear, if you target mass market without central distribution
> >channels, you can not assume that much.
> 
> and that's enough to push hacks into the kernel ? I don't think so. Do 
> it like apple and prevent multi-tasking for any non-apple applications 
> :-p
> 
:) 

It really comes down to a policy decision by the distribution maker.
And I don't think kernel upstream should be the one to force one way or
the other. So merging this patch set will allow android to continue
their work _on mainline_ while everybody else can continue as before.

All points about the impact on the kernel have already been raised. So
you should be happy there. 

Nonetheless, I really think the kernel needs to allow for the android
way of power saving. It misses out on a big feature and a big user-base
if not.

Also I expect there to be synergies between android development and
mainline kernel development _only_ if android development can use
mainline kernel.

And as for the quality of the "hack": I think you find this ugly, just
because you don't like the concept of degrading user space guaranties on
timers and stuff. 

But look at it this way: Suspend blockers are a way for the kernel
to make user space programs accountable for using the resource "power".
If a user space program needs the "traditional" guaranties for
functioning properly, it needs to take a suspend blocker. But _THEN_ it
better be well behaved. This is a kind of contract between userspace
and kernelspace.

On the other hand, if I don't need these traditional guaranties on
timers and stuff, I don't have to know device specific things about
power consumption. I can just use whatever facilities the programming
language provides without needing to worry about low level details.

This is a _big_ plus for attracting 3rd party programs. (And of course
the thing you don't like). 

Cheers,
Flo

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