linux-kernel - Re: [dtc RFC PATCH] Enforce node name unit-address presence/absence

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Message-ID: <523A30FC.3060309@wwwdotorg.org>
Date:	Wed, 18 Sep 2013 17:02:20 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Olof Johansson <olof@...om.net>
CC:	Jon Loeliger <jdl@....com>,
	David Gibson <david@...son.dropbear.id.au>,
	Frank Rowand <frowand.list@...il.com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Rob Herring <rob.herring@...xeda.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Stephen Warren <swarren@...dia.com>
Subject: Re: [dtc RFC PATCH] Enforce node name unit-address presence/absence

On 09/18/2013 02:41 PM, Olof Johansson wrote:
> On Wed, Sep 18, 2013 at 1:23 PM, Stephen Warren <swarren@...dotorg.org> wrote:
>> From: Stephen Warren <swarren@...dia.com>
>>
>> ePAPR 1.1 section 2.2.1.1 "Node Name Requirements" specifies that any
>> node that has a reg property must include a unit address in its name
>> with value matching the first entry in its reg property. Conversely, if
>> a node does not have a reg property, the node name must not include a
>> unit address.
>>
>> Implement a check for this. The code doesn't validate the format of the
>> unit address; ePAPR implies this may vary from binding to binding, so
>> I'm not sure that it's possible to validate the value itself.
...
> Anyway, I think it'd be better to produce warnings than errors for
> this. That way we could also merge it now while the trees are fixed
> up.

Yes, that makes sense.

> Also, maybe warn for @0x<foo>, which is another unpreferred syntax, it
> should just be @<foo> (with foo being in hex).

ePAPR doesn't seem to disallow that; it explicitly says that the
unit-address consists of the characters from table 2-1, which is the
same table of characters used for the node name itself. However, it does
state that the binding for a particular bus may impose additional
restrictions; should I implement such a check but limit it to the root
node or specific known bus types? That would require explicitly
whitelisting the check for a lot of bus types, given that each I2C/...
controller binding is a bus type...
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