linux-kernel - Re: [PATCH] [media] smiapp: make PM functions as __maybe

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Message-ID: <20161027080834.GU9460@valkosipuli.retiisi.org.uk>
Date:   Thu, 27 Oct 2016 11:08:34 +0300
From:   Sakari Ailus <sakari.ailus@....fi>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sebastian Reichel <sre@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH] [media] smiapp: make PM functions as __maybe_unused

Hi Arnd,

On Thu, Oct 27, 2016 at 09:43:16AM +0200, Arnd Bergmann wrote:
> On Thursday, October 27, 2016 10:28:18 AM CEST Sakari Ailus wrote:
> > 
> > On Wed, Oct 26, 2016 at 10:38:01PM +0200, Arnd Bergmann wrote:
> > > The rework of the PM support has caused two functions to
> > > be orphaned when CONFIG_PM is disabled:
> > > 
> > > media/i2c/smiapp/smiapp-core.c:1352:12: error: 'smiapp_power_off' defined but not used [-Werror=unused-function]
> > > media/i2c/smiapp/smiapp-core.c:1206:12: error: 'smiapp_power_on' defined but not used [-Werror=unused-function]
> > > 
> > > This changes all four PM entry points to __maybe_unused and
> > > removes the #ifdef markers for consistency. This avoids the
> > > warnings even when something changes again.
> > > 
> > > Fixes: cbba45d43631 ("[media] smiapp: Use runtime PM")
> > > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > 
> > The power-on sequence is in fact mandatory as it involves writing the
> > initial configuration to the sensor as well.
> > 
> > Instead, I believe the correct fix is to make the driver depend on
> > CONFIG_PM.
> 
> (adding linux-pm list)
> 
> That would be a rather unusual dependency, though it's possible that
> a lot of drivers in fact need it but never listed this explictly in
> Kconfig.
> 
> What do other drivers do that need to have their runtime_resume
> function called at probe time when CONFIG_PM is disabled?

That's certainly possible as well.

V4L2 sub-device core operation s_power() no longer works (as it now uses
runtime PM) but I don't think that's an issue if PM is disabled anyway ---
we should really get rid of that in most drivers.

I can submit a patch.

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@....fi	XMPP: sailus@...iisi.org.uk