linux-kernel - Re: [PATCH 09/14] i2c: Add Device Tree support to the Nomadik I2C driver

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Date:	Thu, 14 Jun 2012 19:57:32 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	Linus Walleij <linus.walleij@...aro.org>,
	linus.walleij@...ricsson.com, arnd@...db.de,
	linux-kernel@...r.kernel.org, grant.likely@...retlab.ca,
	linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 09/14] i2c: Add Device Tree support to the Nomadik I2C
 driver

On 14/06/12 19:36, Mark Brown wrote:
> On Wed, Jun 13, 2012 at 01:28:17PM +0100, Lee Jones wrote:
>
>> Device Tree. However, we have just as much control by keeping them
>> in separate structs in the C file and selecting the right one using
>> the compatible sting.
>
> You're not understanding Linus' point.  The compatible string isn't
> useful here because properties like the maximum clock rate of the bus
> depend on the board design, not the silicon.  The controller may be
> perfectly happy to run at a given rate but other devices on the bus or
> the electrical engineering of the PCB itself may restrict this further.

And you're not understanding mine. ;)

You can have multiple compatible strings for a single driver. Which one 
you reference from the Device Tree will dictate which group of settings 
are used, including variation of clock rates.

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
M: +44 77 88 633 515
Linaro.org │ Open source software for ARM SoCs
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