Re: [RFC PATCH 1/1] of/irq: create interrupts-extended-2 property

[David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>]

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On Mon, Jan 20, 2014 at 05:03:23PM -0800, Olof Johansson wrote:
> On Mon, Jan 20, 2014 at 2:47 PM, Grant Likely <grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
> > On Wed, 15 Jan 2014 16:12:24 +0000, Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org> wrote:
> >> >
> >> > Another, more invasive option would be extend the dts syntax and teach
> >> > dtc to handle property appending. Then the soc dts could stay as it is,
> >> > and the board dts could have something like:
> >> >
> >> >     /append-property/ interrupts = <&intc1 6 1>;
> >> >     /append-property/ interrupt-names = "board-specific-irq";
> >> >
> >> > Both these options solve the issue at the source, are general to other
> >> > properties, and allow more than one level of hierarchy (the proposed
> >> > interrupts-extended-2 only allows one level).
> >>
> >> I've just had a go at implementing the append-property mechanism above
> >> in dtc, and it was far easier than I expected (patch below).
> >>
> >> Does anyone have any issues with the /append-property/ idea?
> >
> > I think that is reasonable.
> 
> 
> The main problem with this (same for clocks) is if you need to append
> something with a name when the original didn't have any.
> 
> Reordering entries might not work for interrupts, since the bindings
> might have requirements on order.
> 
> I'm not aware of a good solution for this. Suggestions welcome.

So, in principle my preferred way to handle things like this would be
to add richer expression support, including a token for "previous
value" when overlaying.

But although I've recently had another look at it, that's still a ways
off, so I wouldn't object to another approach as a stopgap, as long as
its not too hideous.

-- 
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

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