linux-kernel - Re: [PATCH] leds: Fix warnings when PM is disabled for BD2802

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Date:	Sat, 22 Jan 2011 11:21:04 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Richard Purdie <rpurdie@...ys.net>
Subject: Re: [PATCH] leds: Fix warnings when PM is disabled for BD2802

On Saturday, January 22, 2011, Mark Brown wrote:
> On Fri, Jan 21, 2011 at 03:38:37PM -0800, Dmitry Torokhov wrote:
> > On Fri, Jan 21, 2011 at 02:14:02PM -0800, Andrew Morton wrote:
> 
> > >  And it leaves
> > > bd2802_i2c_driver.driver.pm pointing at that all-zeroes instance of
> > > dev_pm_ops, which is rather dangerous.
> 
> > Nothing dagerous here - PM core deals with half-filled pm_ops just fine.
> 
> Indeed, all the PM operations are completly optional so there's no
> problem there except for the empty dev_pm_ops we leave lying around for
> each driver.
> 
> > > If CONFIG_PM_SLEEP=n, the .driver.pm field shouldn't exist at all.

Not if CONFIG_PM_RUNTIME is set (that field is for both SLEEP and RUNTIME).

> > Meh, we have _waaay_ too many config options, I'd rather see CONFIG_PM
> > and possibly CONFIG_PM_SLEEP go, maybe leaving us with
> > CONFIG_PM_RUNTIME and maybe not. How many devices out there do not want
> > PM?

You'd be surprised.

> I made the same point earlier; I guess I'll post an RFC patch over the
> weekend.

The truth is CONFIG_PM was a mistake, because it's practically meaningless
(it basically is always set), so we could remove it, I think, but that
would require us to modify _many_ drivers.

CONFIG_PM_SLEEP is distinctly about suspend and hibernation which people
tend to switch off sometimes.

Thanks,
Rafael
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