"cell-index" vs. "index" vs. no index in I2C device nodes

Josh Boyer jwboyer at linux.vnet.ibm.com
Fri Jun 6 09:59:48 EST 2008


On Thu, 05 Jun 2008 10:50:20 -0500
Timur Tabi <timur at freescale.com> wrote:

> Jochen Friedrich wrote:
> > Hi Timur,
> > 
> >> In situations where it doesn't matter which I2C bus is #1 and which one is #2,
> >> then I think the code should just initialize idx based on the order the nodes
> >> are found in the tree.
> >>
> >> In situations where it does matter, then we should use cell-index.
> > 
> > that's what I did in i2c-cpm, as well. However, here I use the property
> > "linux,i2c-index" instead (see http://patchwork.ozlabs.org/linuxppc/patch?id=18603).
> 
> Well, I just don't see the point of having two different properties that say the
> same thing.  I'm not an IEE 1275 purist, so I don't think we should be hampered
> by old node definitions.  I especially don't like having a property specifically
> for indexing I2C nodes that can't be used to enumerate other nodes.

It's not about purity.  It's about overloading something that has
existing semantics just because you have one usecase that you _think_
needs it.

If everyone did that, this whole device tree concept is going to just
be one big cluster f*ck.  Get over it, fix your driver to use the
device model and aliases propertly, and move on.

josh



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