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

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Message-ID: <20130706120112.GA11069@lukather>
Date:	Sat, 6 Jul 2013 14:01:12 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Arnd Bergmann <arnd@...db.de>
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

Hi,

I'm not exactly sure on what happened to the previous mail that has been
sent empty, but anyway:

On Sat, Jul 06, 2013 at 11:18:00AM +0200, Arnd Bergmann wrote:
> On Saturday 06 July 2013 10:28:04 Maxime Ripard wrote:
> > > 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.
> > 
> > I don't have a strong feeling for one against another, so whatever works
> > best. Both solutions will be a huge improvement anyway 
> > 
> > Just out of curiosity, is there any advantages besides having a fixed
> > property name to the first solution?
> 
> I think it's mostly for consistency: trying to get most subsystems to
> do it the same way to make it easier for people to write dts files.
> 
> A lesser point is that it simplifies the driver code if you don't
> have to pass a name.

So that leave us with mainly one path to achieve this goal:
  - Add a regmap-mtd backend
  - Add DT parsing code for regmap
  - Move the EEPROM drivers from misc to mtd

What other option would we have?

I also thought about writing an EEPROM framework of its own, but the
line is really thin between a large EEPROM and say a small SPI
dataflash, which would make it pretty hard to choose between such a
framework and MTD.

Thanks,
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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