Re: [PATCH 1/4] i2c: introduce i2c-cbus driver

From: Aaro Koskinen
Date: Thu Sep 13 2012 - 10:51:32 EST

On Thu, Sep 13, 2012 at 12:53:09PM +0200, Wolfram Sang wrote:
> On Mon, Sep 03, 2012 at 11:23:22PM +0300, Aaro Koskinen wrote:
> > Add i2c driver to enable access to devices behind CBUS on Nokia Internet
> > Tablets.
> >
> > The patch also adds CBUS I2C configuration for N8x0 which is one of the
> > users of this driver.
> >
> > Cc: linux-i2c@xxxxxxxxxxxxxxx
> > Acked-by: Felipe Balbi <balbi@xxxxxx>
> > Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
> > Signed-off-by: Aaro Koskinen <aaro.koskinen@xxxxxx>
> My main question is: what is CBUS? It doesn't look like an I2C/SMBUS
> host controller, but some bit-banging protocol? As such, it shouldn't go
> to i2c/busses/. And the protocol doesn't look much like I2C, neither.
> There is no ACK/NACK/START/STOP, so I wonder if it should be in i2c
> after all...

It's some legacy 3-wire bus protocol. Not much info is available,
there's some references to CBUS in i2c spec, so I thought it wouldn't
be a completly wrong place for it...

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