Subject: Re: [PATCH] powerpc: add of_find_next_property and of_get_aliased_index

From: Timur Tabi <[email-masked]>
Date: Thu, 26 Jun 2008 10:55:14 -0500

Stefan Roese wrote:
> On Thursday 26 June 2008, Timur Tabi wrote:
>>> The only thing a platform should ever use aliases for is if it needs
>>> to (for whatever purpose) find a specific device, that it cannot
>>> identify otherwise (via "reg", ...).  And then that platform code
>>> should look up the device by the alias, not look up the alias by the
>>> device -- there is no 1-1 mapping from device to alias!
>> Hmmm, I hadn't through about that.  I guess this patch isn't such a great
>> idea after all.  I rescind it.
> 
> Too bad. So now we're back to where we started with the discussion 
> about "cell-index" vs. "index" vs. no index on I2C device nodes. :-(

Well, there's a lot of disagreement on this subject.  Not only do we not agree
on a method of enumerating devices, a lot of people have a problem with the
concept of enumerating them in the first place!

This whole thing started with a problem I had in ASoC V2: identifying an I2C
device by name and number.  Scott W. pointed out that all I need in my "fabric
driver" is a pointer to the i2c_adapter structure that the I2C driver was using.
 If we create a link from the I2C device node to its matching i2c_adapter
structure, then I won't care what the adapter/bus number is.  Unfortunately, it
appears the current I2C code in fsl_soc.c can't handle that, but of_i2c.c can.

-- 
Timur Tabi
Linux kernel developer at Freescale