linux-kernel - RE: [PATCH v3 11/13] of: add property iteration helpers

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Message-ID: <74CDBE0F657A3D45AFBB94109FB122FF04B24A40C8@HQMAIL01.nvidia.com>
Date:	Fri, 26 Aug 2011 08:59:44 -0700
From:	Stephen Warren <swarren@...dia.com>
To:	Jamie Iles <jamie@...ieiles.com>
CC:	Grant Likely <grant.likely@...retlab.ca>,
	Colin Cross <ccross@...roid.com>,
	Erik Gilling <konkers@...roid.com>,
	Olof Johansson <olof@...om.net>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Belisko Marek <marek.belisko@...il.com>,
	Shawn Guo <shawn.guo@...escale.com>,
	Sergei Shtylyov <sshtylyov@...sta.com>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: RE: [PATCH v3 11/13] of: add property iteration helpers

Jamie Iles wrote at Friday, August 26, 2011 3:27 AM:
> On Thu, Aug 25, 2011 at 05:43:42PM -0600, Stephen Warren wrote:
> > This patch adds macros for_each_u32_property_value and
> > for_each_string_property_value, which iterate over an array of values
> > within a device-tree property. Usage is for example:
> >
> > struct of_iter_string_prop iter;
> > for_each_string_property_value(iter, np, "pins")
> >         printk("Got value %s\n", iter.value);
> >
> > Signed-off-by: Stephen Warren <swarren@...dia.com>
> 
> Nicely implemented!

Thanks!

> For the !CONFIG_OF case, I *think* that
> of_iter_u32_prop and of_iter_string_prop can be empty struct's, but I
> wouldn't want to bet money on that!

Empty structs themselves certainly did compile OK, but the code that
uses these macros references iter.value directly, and isn't under #ifdef
CONFIG_OF, so that field has to exist.

I suppose an alternative would be to add an accessor function:

struct of_iter_string_prop iter;
for_each_string_property_value(iter, np, "pins")
        printk("Got value %s\n", of_iter_string_value(iter));

which would return NULL/"" when !CONFIG_OF, and hence allow iter.value
to be removed too. Do you think that's a good approach? It'd be easy to
implement.

-- 
nvpublic

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