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

Jean Delvare khali at linux-fr.org
Tue Oct 16 21:19:39 CEST 2007

On Mon, 15 Oct 2007 22:21:38 -0600, Grant Likely wrote:
> On 10/15/07, David Gibson <david at gibson.dropbear.id.au> wrote:
> > In fact I think it may be acceptle to do the idx++ thing in this
> > situation.  Bus numbers are ugly, but it's not the worst ugliness in
> > the horrible mess that is the Linux i2c subsystem.  It means that bus
> > numbers are theoretically unstable, but that's increasingly true of
> > devices of all sorts - it's up to udev to assign meaningful labels at
> > the user level.

David, after such a rant against the Linux i2c subsystem, I sure hope
that you're going to contribute patches to make it better (whatever you
think needs to be improved, as you didn't say.)

> I think the real problem here comes into play when there are 2 types
> of i2c busses in the system.  If they both maintain their own idx++
> values; then they will conflict.  If an auto assigned bus number is
> used; then it needs to be assigned by the i2c infrastructure; not by
> the driver.

Very true. If you aren't going to define the i2c bus numbers at
platform data level, then you shouldn't be defining them _at all_.
Don't use i2c_add_numbered_adapter, use i2c_add_adapter and let
i2c-core choose an appropriate a bus number.

Jean Delvare

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