linux-kernel - Re: [PATCH] [POWERPC] Add i2c pins to dts and board setup

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Date:	Wed, 21 May 2008 18:17:06 +0200
From:	Jochen Friedrich <jochen@...am.de>
To:	Scott Wood <scottwood@...escale.com>
CC:	Anton Vorontsov <avorontsov@...mvista.com>,
	linuxppc-dev list <linuxppc-dev@...abs.org>,
	"Kernel, Linux" <linux-kernel@...r.kernel.org>,
	Kumar Gala <galak@...nel.crashing.org>,
	Linux I2C <i2c@...sensors.org>,
	Jean Delvare <khali@...ux-fr.org>,
	Paul Mackerras <paulus@...ba.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] [POWERPC] Add i2c pins to dts and board setup

Hi Scott,

>> +   - linux,i2c-index : Can be used to hard code an i2c bus number.
>> +   - linux,i2c-class : Can be used to override the i2c class.
>
> Why do we need this?

There are still a bunch of i2c drivers using the old API (mainly v4l and dvb stuff)
which are slowly being converted by their subsystem maintainers, though.

> It'd be better to just convert any needed old-style drivers than add this
> to the device tree.

Sure. That's why the parameters are only optional. Once all i2c drivers are
converted, these parameters won't be used anymore. Maybe they should be marked
as deprecated.

>> +   - bus-frequency : Can be used to set the i2c bus frequency. If unspecified,
>> +     a default frequency of 60kHz is being used.
> 
> clock-frequency is the standard name for such things.

I was just confused by the fact that unlike a serial port, i2c is a bus itself.

Thanks,
Jochen
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