linux-kernel - Re: [RFC PATCH 2/2] dt: spi: s3c64xx: add compatible to controller-data

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Date:	Wed, 29 Jul 2015 20:21:34 +0200
From:	Michal Suchanek <hramrach@...il.com>
To:	Mark Brown <broonie@...nel.org>
Cc:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Padmavathi Venna <padma.kvr@...il.com>,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	devicetree <devicetree@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	MTD Maling List <linux-mtd@...ts.infradead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	linux-spi <linux-spi@...r.kernel.org>
Subject: Re: [RFC PATCH 2/2] dt: spi: s3c64xx: add compatible to controller-data

On 29 July 2015 at 19:16, Mark Brown <broonie@...nel.org> wrote:
> On Wed, Jul 29, 2015 at 06:19:24PM +0200, Michal Suchanek wrote:
>> On 29 July 2015 at 16:00, Mark Brown <broonie@...nel.org> wrote:
>
>> > I can't tell from this commit message what the issue you're trying to
>> > fix is, sorry.  Nodes without compatible strings are entirely normal and
>> > don't need compatible strings.  It sounds like a bug in whatever other
>> > driver is becoming confused.
>
>> The driver that gets confused is ofpart.
>
>> The two-line patch to allow it to just ignore controller-data has been
>> rejected on the basis that s3c64xx should use a compatible string
>> because ofpart monopolizes all nodes without compatible which are
>> children of a mtd device. Devicetrees containing such nodes that are
>> not partitions are presumably invalid and should be rejected when
>> ofpart is compiled into the kernel.
>
> That seems like an extremely limited binding, the normal thing here
> would be to create a specifically named node to contain the collection
> of subnodes like many PMICs do for their regulators.  As a fix I'd
> suggest just silently ignoring nodes it can't understand, or printing a
> warning if that's a serious issue.
>
>> >> +     if (!of_get_property(data_np, "compatible", NULL) ||
>> >> +         strcmp(of_get_property(data_np, "compatible", NULL),
>> >> +                "samsung,s3c-controller-data"))
>> >> +             dev_err(&spi->dev, "child node 'controller-data' does not have correct compatible\n");
>
>> > This will break all existing users which is not acceptable for
>> > mainline, we need to preserve compatibility with existing device trees.
>
>> It will not break anything. It will just spam dmesg.
>
> I'm confused - if all this change does is to spam dmesg then what's the
> point?

Presumably when your SPI NOR flash fails to probe this message will be
just above and you will look into the binding doc and add the
compatible.

Thanks

Michal
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