linux-kernel - Re: [PATCH v6 4/8] of: Reduce indentation in of_graph_get_next

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Message-ID: <1688746.6CaQoSDOni@avalon>
Date:	Mon, 10 Mar 2014 20:19:44 +0100
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Philipp Zabel <p.zabel@...gutronix.de>
Cc:	Grant Likely <grant.likely@...aro.org>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Rob Herring <robh+dt@...nel.org>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Guennadi Liakhovetski <g.liakhovetski@....de>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v6 4/8] of: Reduce indentation in of_graph_get_next_endpoint

Hi Philipp,

On Friday 07 March 2014 18:40:54 Philipp Zabel wrote:
> Am Freitag, den 07.03.2014, 01:12 +0100 schrieb Laurent Pinchart:
> > Hi Philipp,
> > 
> > Thank you for the patch.
> > 
> > I've submitted a fix for the of_graph_get_next_endpoint() function, but it
> > hasn't been applied yet due to the patch series that contained it needing
> > more work.
> > 
> > The patch is available at https://patchwork.linuxtv.org/patch/21946/. I
> > can rebase it on top of this series, but I still wanted to let you know
> > about it in case you would like to integrate it.
> 
> Thank you for the pointer. A pity about the timing, this will mostly
> revert my indentation patch. I'd be glad if you could rebase on top of
> the merged series.
> 
> While we look at of_graph_get_next_endpoint(), could you explain the
> reason behind the extra reference count increase on the prev node:
>
> 	/*
> 	 * Avoid dropping prev node refcount to 0 when getting the next
> 	 * child below.
> 	 */
> 	of_node_get(prev);
>
> This unfortunately makes using the function in for_each style macros a
> hassle. If that part wasn't there and all users that want to keep using
> prev after the call were expected to increase refcount themselves,
> we could have a
>
> #define of_graph_for_each_endpoint(parent, endpoint) \
> 	for (endpoint = of_graph_get_next_endpoint(parent, NULL); \
> 	     endpoint != NULL; \
> 	     endpoint = of_graph_get_next_endpoint(parent, endpoint))

I don't know what the exact design decision was (Sylwester might know), but I 
suspect it's mostly about historical reasons. I see no reason that would 
prevent modifying the current behaviour to make a for-each loop easier to 
implement.

-- 
Regards,

Laurent Pinchart

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