linux-kernel - Re: [PATCH v2 13/11] mtd: assign mtd->dev.of

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Message-ID: <20151120025842.GT64635@google.com>
Date:	Thu, 19 Nov 2015 18:58:42 -0800
From:	Brian Norris <computersforpeace@...il.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	linux-mtd@...ts.infradead.org,
	Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
	Marek Vasut <marex@...x.de>,
	Scott Wood <scottwood@...escale.com>,
	Josh Wu <josh.wu@...el.com>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Han Xu <han.xu@...escale.com>, Stefan Agner <stefan@...er.ch>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 13/11] mtd: assign mtd->dev.of_node when creating
 partition devices

On Thu, Nov 12, 2015 at 02:22:20PM +0100, Boris Brezillon wrote:
> On Wed, 11 Nov 2015 16:15:50 -0800
> Brian Norris <computersforpeace@...il.com> wrote:
> > IOW, I think we can grab the reference in add_mtd_device() and drop it
> > in del_mtd_device(). This would handle both the partition and
> > non-partition case the same.
> 
> Hm, actually I think we need it. When you iterate over child nodes with
> for_each_child_of_node(), the node is released (of_node_put() is
> called) after each iteration. While this is not a problem for mtd
> device registration (because the controller usually retain the
> reference when add_mtd_device() is called), this is not true for the
> partitions. And if the partitions are ever defined using an overlay,
> this can be a problem.

Yep.

> To sum-up, I think we should retain the node reference until
> add_mtd_device() has retained it, so maybe we should have a ->cleanup()
> function in mtd part parsers.

OK. I'll drop my patch and send out my ->cleanup() stuff instead, so you
can patch on top of that.

Brian
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