[PATCH 2/2] i2c: Add devtree-aware iic support for PPC4xx

[Grant Likely]

On 10/15/07, Eugene Surovegin <ebs at ebshome.net> wrote:
> On Mon, Oct 15, 2007 at 01:53:40PM -0500, Scott Wood wrote:
> > Though, I don't see what the problem with the original approach is, as long
> > as the numbers are chosen in the same way when registering i2c clients based
> > on the children of the adapter node.  There's no concept in the hardware
> > itself of a bus number.
>
> Huh? As far as I can tell, there is. Also, I want messages from the
> kernel mention something I can map to the real hw, e.g. fixed IIC
> device index, not some random number.

Yes, in the same way that there may be more than one on-chip serial or
ethernet controllers.  However, it does not necessarily follow that
the *logical* bus number will match the way on chip devices are
numbered.

Example: Suppose you have a board with 2 chips which each include 2
i2c controllers.  Each chip numbers them 1 & 2.  So, which chip gets
1-2 and which one gets 3-4?

>
> This already works with the current OCP code, so if you want change
> it to a "superior" technology, please, make sure it provides the same
> functionality as trivial OCP one.

agreed

> I find it rather puzzling that instead people are trying to make
> this a non-issue as soon as it cannot be implemented easily with
> their new and shiny infrastructure.

No, it is a real problem; and not just for i2c.  We need a solution for it.

Cheers,
g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
grant.likely at secretlab.ca
(403) 399-0195