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

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Message-ID: <20150729171613.GI11162@sirena.org.uk>
Date:	Wed, 29 Jul 2015 18:16:13 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Michal Suchanek <hramrach@...il.com>
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 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?

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