linux-kernel - Re: [PATCH v3] Input: tsc2005

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Message-ID: <5143701.zqn4HuBlp3@wuerfel>
Date:	Fri, 30 Oct 2015 11:40:04 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Michael Welling <mwelling@...e.org>
Cc:	Mark Brown <broonie@...nel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	kbuild test robot <lkp@...el.com>, kbuild-all@...org,
	Tony Lindgren <tony@...mide.com>, Pavel Machek <pavel@....cz>,
	Felipe Balbi <balbi@...com>,
	Sebastian Reichel <sre@...nel.org>,
	Roger Quadros <rogerq@...com>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH v3] Input: tsc2005 - Add support for tsc2004

On Thursday 29 October 2015 20:01:51 Michael Welling wrote:
> On Fri, Oct 30, 2015 at 09:39:05AM +0900, Mark Brown wrote:
> > On Thu, Oct 29, 2015 at 03:23:31PM -0700, Dmitry Torokhov wrote:
> > 
> > > However, you have regmap in the driver core already. Mark, is it
> > > possible to have regmap API also allow doing raw underlying protocol
> > > transfer so that consumers could issue command requests without needing
> > > to know if they need to do it over i2c or spi or whatever. Or we need a
> > > notion of command registers in regmap...
> > 
> > I don't think it's a good idea to break the encapsulation of the regmap
> > and export the raw I/O functionality directly, there seem to be more bad
> > ways of using that than good.  The driver must at some point know what
> > bus it is dealing with and be able to manage this itself.
> > 
> > I don't know what "command registers" are.
> 
> With this device, if the MSB of the first byte of the transaction is 1 then
> a convertor command is encoded in that byte instead of a register address.
> 
> So here is my plan:
> - Add a function pointer for tsc2005_cmd in the struct tsc2005
> - Put the spi and i2c tsc2005_cmd versions in their respective drivers
> - Pass the cmd functions to the core via tsc200x_probe
> 
> Any objections?

Sounds good. If you end up needing more than one function pointer,
better pass a 'const' pointer to a structure of function pointers that
you can declare statically in the driver.

> Other review suggestions before I code the revision?
> Am I doing too much with a single patch?

Yes.

Please split out the DT binding changes into a separate patch, and
start with one patch that just moves the common parts out of the SPI
driver before you add the new driver.

	Arnd
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