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

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Date:	Thu, 13 May 2010 15:45:03 -0700
From:	Greg KH <gregkh@...e.de>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Daniel Walker <dwalker@...o99.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Matthew Garrett <mjg@...hat.com>,
	Brian Swetland <swetland@...gle.com>,
	Paul Walmsley <paul@...an.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Tony Lindgren <tony@...mide.com>,
	Kevin Hilman <khilman@...prootsystems.com>,
	Alan Stern <stern@...land.harvard.edu>, magnus.damm@...il.com,
	Theodore Ts'o <tytso@....edu>,
	mark gross <mgross@...ux.intel.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Geoff Smith <geoffx.smith@...el.com>,
	Benoît Cousson <b-cousson@...com>,
	linux-omap@...r.kernel.org, Vitaly Wool <vitalywool@...il.com>,
	Liam Girdwood <lrg@...mlogic.co.uk>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)

On Thu, May 13, 2010 at 11:27:49PM +0100, Mark Brown wrote:
> On Thu, May 13, 2010 at 02:46:53PM -0700, Greg KH wrote:
> > On Thu, May 13, 2010 at 02:33:29PM -0700, Daniel Walker wrote:
> 
> > > You get the driver mainlined, then maintain a small patch to add
> > > wakelocks. Not hard at all , with lots of incentive to do so since you
> > > don't have to maintain such a large block of code out of tree.
> 
> > Sorry, but it doesn't seem to work that way.  Look at the large number
> > of out-of-tree android device drivers that remain sitting there because
> > of the lack of this interface being in the kernel.
> 
> Is that really the issue?  The ones I've looked at have mostly suffered
> from being built on 2.6.29 and needing refreshes for current kernel APIs
> or from general code quality issues - I don't recall ever looking at one
> and thinking that the wakelocks were the one issue.

Yes, it is an issue.  See the mess that we have had in trying to get
some of the original G1 drivers merged in the staging tree for proof of
this.

> > Also note that such a driver, without wakelocks, would never get tested,
> > and so, things start quickly diverging.
> 
> Chances are that if the driver is useful people will start using it in
> non-Android systems anyway.

No, not usually.  Do you really think that someone else is going to use
the G1 camera driver for anything else?  :)

> As people have already observed wakelocks needn't have any practical
> effect on the running system so if the drivers are broken without
> wakelocks they'd be broken anyway.  
> 
> If this really is a big concern with getting drivers into mainline then
> surely we could just add some noop wakelock functions for the drivers to
> call?  It's not particularly pretty but it'd deal with the driver merge
> side of things.

I fail to see why getting the real functionality of the wakelocks into
the kernel is a problem.  Especially as they fit a real need, and work
well for that.

thanks,

greg k-h
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