linux-kernel - Re: [PATCH 2/2] mfd: twl4030: add twl4030-pwrbutton as our child

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Date:	Fri, 27 Feb 2009 15:42:20 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	David Brownell <david-b@...bell.net>
Cc:	me@...ipebalbi.com, linux-kernel@...r.kernel.org,
	linux-input@...r.kernel.org, felipe.balbi@...ia.com,
	sameo@...nedhand.com
Subject: Re: [PATCH 2/2] mfd: twl4030: add twl4030-pwrbutton as our child

On Fri, 27 Feb 2009 15:20:56 -0800
David Brownell <david-b@...bell.net> wrote:

> On Friday 27 February 2009, Andrew Morton wrote:
> > > > 
> > > > What has gone wrong here?
> > > 
> > > Not much I can see. __It's registering a platform_device,
> > > but only if it could be used on this system.
> > 
> > Again, that all gets fixed if this is done the right way around. __Run
> > your probe function. __If the hardware is there, register with the core
> > and all the nodes appear. __If the hardware is not present: bale.
> 
> Right.  If there's no button hooked up to its "power button"
> signal, don't register that "twl4030-pwrbutton" node.
> 
> 
> > The design of the whole subsystem appears to be upside down :(
> 
> You seem to be missing something.  Is it only the lack of that
> tweak Felipe sent?

I generally just delete unchangelogged patches.

<goes back and finds it>


That doesn't address the problem at all.  A function called
"add_children" just shouldn't exist.  The general kernel design is for
client drivers to register themselves with the core, so the core does
not have any hard-wired knowledge of any client drivers.

IOW, twl4030_pwrbutton_probe() should call into twl4030-core,
registering the powerbutton driver.

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