Re: [PATCH 2/2] Warn on node name unit-addresses with '0x' or leading 0s

From: David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>
To: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: devicetree-compiler-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	"devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH 2/2] Warn on node name unit-addresses with '0x' or leading 0s
Date: Tue, 23 Feb 2016 16:47:46 +1100	[thread overview]
Message-ID: <20160223054746.GT2808@voom.fritz.box> (raw)
In-Reply-To: <CAL_JsqLDdyLd4z_Pmsr7+vtnMZsusEpJYZ4tdZmjQFt0PD_Fbw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

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On Mon, Feb 22, 2016 at 10:51:46AM -0600, Rob Herring wrote:
> On Thu, Feb 18, 2016 at 11:07 PM, David Gibson
> <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org> wrote:
> > On Thu, Feb 11, 2016 at 02:46:59PM -0600, Rob Herring wrote:
> >> Node name unit-addresses should never begin with 0x or leading 0s
> >> regardless of whether they have a bus specific address (i.e. one with
> >> commas) or not. Add warnings to check for these cases.
> >
> > Hmm.. I'm pretty sure that's true in practice, but it's not true in
> > theory.  A bus could define it's unit address format just about
> > however it wants, including with leading 0s.
> 
> Only if it is not reviewed... This whole check is about what best
> practices are, not what is possible.

Hmm.  dtc checks are really about checking for best practice at the
level of individual dts files, though, not bindings.

> > I think a better approach would be to add a test specific to
> > simple-bus devices (by looking at compatible on the parent) that fully
> > checks the unit address.
> >
> > From there we can start adding tests for other bus types.
> 
> simple-bus is easy enough,

So, start with that, then tackle the next problem.

> but then next up would be I2C and SPI. We
> can't generically tell if a node is on I2C or SPI bus.

Why not?  Or perhaps.. how generically do you need?  I think having a
big list of i2c / spi controllers would be acceptable here, if not
ideal.

> If we do have
> some bus with wacky addresses, it should definitely have a bus
> compatible and then we can simply exclude it from the check.
> 
> Another option would be skipping the test if there are any commas (or
> periods, etc.) in the unit address. That's pretty rare to begin with
> and a single number is pretty much not a bus specific unit-address.

Um.. no.. there are definitely bus types that don't typically use
commas.  ISA, for one.

-- 
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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