linux-kernel - Re: MTD EEPROM support and driver integration

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Message-Id: <201307060033.13259.arnd@arndb.de>
Date:	Sat, 6 Jul 2013 00:33:13 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Artem Bityutskiy <dedekind1@...il.com>,
	Shawn Guo <shawn.guo@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	oliver@...inagl.nl, linux-mtd@...ts.infradead.org
Subject: Re: MTD EEPROM support and driver integration

On Saturday 06 July 2013, Maxime Ripard wrote:
> > My first thought is that it should be more generic than that and not
> > have the mac address hardcoded as the purpose. We could possibly use
> > regmap as the in-kernel interface, and come up with a more generic
> > way of referring to registers in another device node.
> 
> Hmm, I maybe wasn't as clear as I wanted. Here mac-storage was just an
> example. It should indeed be completely generic, and a device could have
> several "storage source" defined, each driver knowing what property it
> would need, pretty much like what's done currently for the regulators
> for example.
> 
> We will have such a use case anyway for the Allwinner stuff, since the
> fuses can be used for several thing, including storing the SoC ID,
> serial numbers, and so on.

Ah, I see. In general, we have two ways of expressing the same thing
here:

a) like interrupts, regs, dmas, clocks, pinctrl, reset, pwm: fixed property names

	regmap = <&at25 0xstart 0xlen>;
	regmap-names = "mac-address";

b) like gpio, regulator: variable property names

	mac-storage = <&at25 0xstart 0xlen>;

It's unfortunate that we already have examples of both. They are largely
equivalent, but the tendency is towards the first.

	Arnd
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