linux-kernel - Re: [PATCH 0/8] Suspend block api (version 6)

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Message-ID: <20100506002125.GA22013@sirena.org.uk>
Date:	Thu, 6 May 2010 01:21:25 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	tytso@....edu, Matthew Garrett <mjg@...hat.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Brian Swetland <swetland@...gle.com>,
	Kevin Hilman <khilman@...prootsystems.com>,
	Arve Hj?nnev?g <arve@...roid.com>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Paul Walmsley <paul@...an.com>, magnus.damm@...il.com,
	mark gross <mgross@...ux.intel.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Geoff Smith <geoffx.smith@...el.com>, rebecca@...roid.com
Subject: Re: [PATCH 0/8] Suspend block api (version 6)

On Thu, May 06, 2010 at 01:33:59AM +0200, Rafael J. Wysocki wrote:

> set up that way).  Even without the patchset you may implement a power
> manager in user space that will suspend the system whenever it thinks it's
> idle.

Clearly, but...

> On Thursday 06 May 2010, Mark Brown wrote:

> > In the primary existing application this change interoperates very poorly
> > with at least the current audio subsystem since that handles suspend by
> > ceasing all activity and powering as much as it can off, which is sensible for
> > manual only suspends but highly undesirable for opportunistic suspend in
> > phones.

> You said that there's no fundamental difference between manual and
> opportunistic suspend.  It only matters what _you_ are going to use suspend
> for.  I agree that at the moment it's not suitable for aggressive power
> management in phones because of the audio problem, but that applies to
> "manual" as well as to "opportunistic" suspend.

...on the other hand there's exactly one existing application for this,
and that's the one that's most likely to run into problems since it's a
phone OS and aggressive power management is pretty important for phones.

Merging a feature into mainline makes it much more something which one
would expect to play nicely with the rest of the kernel - if it's
something that isn't part of the standard kernel or userspaces it's much
less surprising that additional changes may be required to produce a
well integrated system.

> You're saying that suspend is not suitable for one particular purpose in its
> current form, which is entirely correct, but that doesn't imply that the
> patchset is wrong.

As I keep saying I agree that merging this is reasonable given the
additional power savings it brings in practical systems today.  As I
also keep saying I do want to have some understanding about what the
story is for dealing with the problems so that people can easily use
this feature out of the box.

Like I say, my current impression is that the best approach is for
affected subsystems or drivers to implement a custom solution - does
that match your understanding and that of the other PM maintainers?
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