linux-kernel - Re: [PATCH v2 1/2] regulator: act8945a: add regulator driver for ACT8945A

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Date:	Thu, 14 Jan 2016 12:43:00 +0100
From:	Peter Korsgaard <peter@...sgaard.com>
To:	"Yang\, Wenyou" <Wenyou.Yang@...el.com>
Cc:	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	"Rob Herring" <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"Kumar Gala" <galak@...eaurora.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	"devicetree\@vger.kernel.org" <devicetree@...r.kernel.org>,
	"Ferre\, Nicolas" <Nicolas.FERRE@...el.com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	Javier Martinez Canillas <javier@...hile0.org>,
	Lee Jones <lee.jones@...aro.org>,
	"linux-arm-kernel\@lists.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/2] regulator: act8945a: add regulator driver for ACT8945A

>>>>> "Yang," == Yang, Wenyou <Wenyou.Yang@...el.com> writes:

Hi,

>> 
 >>> Isn't the regulator part of the act8945a identical to act8865? Can't we just use
 >>> the existing act8865-regulator.c driver? (E.G. support 8865 variant in the mfd
 >>> driver, but only register the regulator sub device?)
 >> 
 >> > Yes, the regulator part of the act8945a is identical to act8865.
 >> 
 >> > But the act8865-regulator driver is a struct i2c_driver, and the mfd  > sub-
 >> device driver is a platform_driver driver, it is not easy to use  > it.
 >> 
 >> But the mfd driver could support the act8865 variant as well (by only registering
 >> the regulator mfd cell).

 > I still don't understand.

 > The MFD sub device is registered as a platform device, the existing
 > act8865 driver is registered as an i2c_driver. How do they match? :)

 > Could you point out which exiting driver for me to reference.  Thank you!

What I'm saying is that it isn't nice that we end up with both
act8865-regulator.c and act8954-regulator.c doing 95% the same. This can
either be fixed by:

- Adding act8865 support to your mfd driver (but only registering the
  regulator subdev for act8865) and changing the existing
  act8865-regulator driver to work as a mfd subdev (platform device)

- Extending the act8865-regulator driver to register as a platform
  driver in ADDITION to a i2c driver so it can be used with mfd. The
  driver already uses regmap so it should only be a matter of adding the
  pdev probe/remove functions.

-- 
Venlig hilsen,
Peter Korsgaard