Re: [PATCH] Device tree bindings for Xilinx devices

["Grant Likely" <grant.likely@secretlab.ca>]

On 10/10/07, David Gibson <dwg@au1.ibm.com> wrote:
> > My main concern is that I don't like the implicit numbering that
> > occurs simply based on the order of devices in the device tree.  If
> > the probe algorithm ever changes to parse in reverse order or
> > something reorders the tree, then the device numbers also change.  :-(
>
> Way of the future, apparently, everything's supposed to use udev to
> give things logical names.  No, I'm not thrilled at the prospect
> either.

...

So in the OF aliases approach, would udev need to read the aliases
node when assigning names to devices?

>
> > I'd rather be explicit.  In fact I've already been bitten by this
> > where the mpc5200 has 6 PSC, each of which can be configured as a
> > serial port.  However, I've got access to 3 different boards; each of
> > which has the logical port numbers 100% unrelated to the 'cell'
> > number.
>
> In any case, this can't really belong in a *device* binding.  Because
> the numbering has to cross devices of the same basic type, but
> different implementations.  Where "basic type" is based on how device
> names are allocated, and is thus inherently Linux specific.

Okay, that makes sense.

> > > Segher's suggestion of using OF-style aliases for this is a fairly
> > > good one, actually.  I just need to get to implementing it...
> >
> > /me needs to look up what that look like and how I would use it.  My
> > knowledge of OF is sadly lacking.
>
> Short version by example:
> / {
>         /* ... */
>         aliases {
>                 hd = "/pci@f0000000/sata@f4000000/....";
>                 enet0 = "/soc/ethernet@c000";
>                 enet1 = "/soc/ethernet@d000";
>                 enet2 = "/pci@f0000000/isa/ethernet@i480"
>                 ttya = "/soc/serial@e000";
>                 ttyb = "/pci/isa/serail@3f8";
>         }
> }

Ah, my plan worked...  I got you to teach me about OF aliases and I
have to do any work myself.  :-)

Hmm, yes that would provide the information nicely.  As long as the
data is in the tree, I'm pretty happy.

Cheers,
g.

>
> --
> David Gibson                    | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
>                                 | _way_ _around_!
> http://www.ozlabs.org/~dgibson
>


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