linux-kernel - Re: [PATCH 1/2] regulator: Add brcm,bcm63xx-regulator device tree binding

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Date:	Thu, 3 Dec 2015 00:06:31 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Simon Arlott <simon@...e.lp0.eu>
Cc:	devicetree@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>,
	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>,
	linux-kernel@...r.kernel.org,
	Florian Fainelli <f.fainelli@...il.com>,
	Jonas Gorski <jogo@...nwrt.org>
Subject: Re: [PATCH 1/2] regulator: Add brcm,bcm63xx-regulator device tree
 binding

On Wed, Dec 02, 2015 at 08:26:36PM +0000, Simon Arlott wrote:
> On 02/12/15 12:53, Mark Brown wrote:

> > This is the sort of thing you can pick up from the SoC compatible
> > strings.  As things stand there is zero content in this driver that
> > relates to this SoC.

> There's always going to be very little content in the driver that
> relates to this SoC, given that a single bit flip enables/disables
> power.

> All other device tree drivers allow a register address to be specified
> for the device, how is an offset in the regmap any different?

It's not that it's an offset in regmap, it's that you're trying to make
a device driver with literally *no* content that is specific to the
actual device.  If you're making a driver for a specific device like
this it should know at least something about how to control the device
from the compatible string.  If you're making a generic driver it should
not make reference to specific devices.

In general I would prefer to have a driver with a SoC specific
compatible string and the data tables in the kernel, that way we keep
the device trees stable and our ABI more robust.

> >> The mask is used as there's one bit per regulator in the register, but
> >> there's more than one way to express this in the DT:

> > I wouldn't expect to see it in the device tree at all for a device
> > specific driver.

> If there isn't an individual entry in DT for each regulator, how is it
> supposed to work? There's no #regulator-cells property.

There could be one if it would help, but we do normally manage to do
this without - look at how other regulator drivers work.

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