linux-kernel - Re: [PATCH v4 1/2] regulator: act8945a: add regulator driver for ACT8945A

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Message-ID: <CABxcv=kNKmgRytxB5ppawrAvC-GDRhV4T_UUGvpHgKp9+BsUmQ@mail.gmail.com>
Date:	Fri, 29 Jan 2016 08:50:19 -0300
From:	Javier Martinez Canillas <javier@...hile0.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	"Yang, Wenyou" <Wenyou.Yang@...el.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Lee Jones <lee.jones@...aro.org>,
	Peter Korsgaard <jacmet@...il.com>,
	"Ferre, Nicolas" <Nicolas.FERRE@...el.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 1/2] regulator: act8945a: add regulator driver for ACT8945A

Hello Mark,

On Fri, Jan 29, 2016 at 8:35 AM, Mark Brown <broonie@...nel.org> wrote:
> On Fri, Jan 29, 2016 at 01:20:08AM +0000, Yang, Wenyou wrote:
>
>> > > +static const struct of_device_id act8945a_pmic_of_match[] = {
>> > > + { .compatible = "active-semi,act8945a-regulator" },
>> > > + { },
>> > > +};
>> > > +MODULE_DEVICE_TABLE(of, act8945a_pmic_of_match);
>
>> > This seems mostly OK but why do we have a compatible string here - shouldn't
>> > the MFD be able to instantiate the regulator function without needing this?
>
>> Because I got feedback from Javier for the act8945a-charger patches of this MFD series,
>> He said missing the OF match table will cause the module autoloading broken.
>
>> http://lists.infradead.org/pipermail/linux-arm-kernel/2016-January/398113.html
>
>> What do you think about it?
>
> If then device is not being loaded from the DT (and it shouldn't be, the
> device looks like it should be instantiated directly by the MFD as it
> can't exist separately to that MFD) an OF table will do nothing.

Then he should remove the .of_compatible from the MFD cell definition.

Otherwise the MFD core will assign an of_node to this device in
mfd_add_device(), making the platform core to believe the device was
instantiated by OF. So an OF modalias uevent will be reported to load
the module and the OF table should be used for matching the device
with the driver.

IOW, the MFD and regulator driver have to agree on this. Either
everything should have OF or platform information, both work but
mixing these as it was on a previous version doesn't.

Best regards,
Javier