linux-kernel - Re: [PATCH 9/9] mfd: ab8500-core: Pass GPADC compatible string to MFD core

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Date:	Tue, 14 May 2013 10:26:14 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Linus WALLEIJ <linus.walleij@...ricsson.com>,
	Srinidhi KASAGAR <srinidhi.kasagar@...ricsson.com>,
	Samuel Ortiz <sameo@...ux.intel.com>
Subject: Re: [PATCH 9/9] mfd: ab8500-core: Pass GPADC compatible string to
 MFD core

On Tue, 14 May 2013, Linus Walleij wrote:

> On Wed, May 8, 2013 at 3:29 PM, Lee Jones <lee.jones@...aro.org> wrote:
> 
> > When booting with Device Tree enabled the MFD core uses each device's
> > compatible string to find and allocate its associated of_node pointer,
> > which in turn is passed to the driver via the platform_device struct.
> > Without it, the driver won't be able to interrogate the Device Tree or
> > locate suitable regulators and will most likely fail to probe.
> >
> > Cc: Samuel Ortiz <sameo@...ux.intel.com>
> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> 
> Can you explain what regression this is causing since the GPADC
> driver (drivers/mfd/ab8500-gpadc.c) does not support device tree

Yes it does. :)

> probing and does not have an .of_match_table defined in it's
> driver struct? I mean, what could possibly match that
> compatible string? The .name field will take care of naming
> the device does it not?

You only need that stuff if you require _extra_ bindings. Things like
regulators and interrupt numbers are configured behind the scenes.

> For non-emergency merging though:
> Acked-by: Linus Walleij <linus.walleij@...aro.org>

If we don't put this into v3.10-rcX, then the GPADC driver will be
broken in v3.10 when booting with DT.

> Since it matches the example in
> Documentation/devicetree/bindings/mfd/ab8500.txt
> 
> But for this to make sense the AB8500 ADC driver needs
> to be augmented for DT probing and preferrably also moved
> to drivers/adc and made to utilize that subsystem.

Not sure I understand the reasoning for this. It works well as a plain
MFD device.

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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