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

From: Scott Wood <[email-masked]>
Date: Mon, 15 Oct 2007 15:45:04 -0500

Grant Likely wrote:
> On 10/15/07, Scott Wood <[email-masked]> wrote:
>> Don't Do That(tm).  If you use this mechanism, and an adapter node
>> doesn't have a bus number, then it doesn't get to pre-register devices,
>> but instead must use i2c_new_device.
> 
> Even that doesn't work.  For example if a PCI device is probed which
> registers an i2c bus; there needs to be a mechanism for the i2c layer
> to know that an id is already spoken for, so once again there needs to
> be a mechanism to map easily from id to device (or lack thereof).

As long as all statically-assigned buses have their devices passed to 
i2c_register_board_info by platform code before the PCI device is 
probed, the i2c layer will hand out bus numbers that don't conflict.

> Where user == system integrator or firmware engineer.  ie. boards with
> no-populate options which affect the numbering; changes to match the
> silkscreening on the chassis when a common board is used by multiple
> systems.  It's a conceivable scenario.  (Again; this is more relevant
> to eth and serial devices than i2c).

Sure, but I guess I don't see the problem with such a person editing the 
label property.  The label property also gives more freedom in terms of 
which characters can be used in the description.

Aliases could still be used when there's a higher level abstraction 
related to purpose, not identification.

-Scott