linux-kernel - Re: [PATCH 04/11] mtd: ofpart: do not fail probe when no partitions exist

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Date:	Tue, 23 Jun 2015 11:26:33 -0700
From:	Brian Norris <computersforpeace@...il.com>
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>,
	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Han Xu <han.xu@...escale.com>, Mark Brown <broonie@...nel.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Marek Vasut <marex@...x.de>,
	Rafał Miłecki <zajec5@...il.com>,
	Alison Chaiken <alison_chaiken@...tor.com>,
	Huang Shijie <b32955@...escale.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Knut Wohlrab <knut.wohlrab@...bosch.com>,
	Bean Huo 霍斌斌 (beanhuo) 
	<beanhuo@...ron.com>, "grmoore@...era.com" <grmoore@...era.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, dmaengine@...r.kernel.org,
	linux-mtd@...ts.infradead.org, linux-spi@...r.kernel.org
Subject: Re: [PATCH 04/11] mtd: ofpart: do not fail probe when no partitions
 exist

On Wed, Jun 03, 2015 at 09:26:40PM -0000, Michal Suchanek wrote:
> On Exynos it is necessary to set SPI controller parameters that apply to
> a SPI slave in a DT subnode of the slave device. The ofpart code returns
> an error when there are subnodes of the SPI flash but no partitions are
> found. Change this condition to a warning so that flash without
> partitions can be accessed on Exynos.

So judging by the subsequent discussion, you're looking at handling
nodes like this:

	flash@... {
		compatible = "m25p80";
		...

		controller-data {
			samsung,spi-feedback-delay = <0>;
		};
	};

Now, I'm not a real fan of this controller-data node in the first place
(did that binding get reviewed?). But this is especially bad since
we now have collisions on what to do with subnodes that don't have a
compatible property. By legacy, ofpart has already claimed ownership of
subnodes of an MTD node, where the subnode does not have a compatible
property. See Documentation/devicetree/bindings/mtd/partition.txt:

  "NOTE: if the sub-node has a compatible string, then it is not a
  partition."

So it seems the natural solution is to just define a proper
compatibile property for this subnode, and ofpart.c will naturally
handle this. See:

commit e79265ba6bdb31437bd4c3e7911950f9d1262a07
Author: Josh Wu <josh.wu@...el.com>
Date:   Mon Aug 5 19:14:38 2013 +0800

    mtd: ofpart: add compatible check for child nodes



Brian

> Signed-off-by: Michal Suchanek <hramrach@...il.com>
> ---
>  drivers/mtd/ofpart.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/ofpart.c b/drivers/mtd/ofpart.c
> index aa26c32..a29d29f 100644
> --- a/drivers/mtd/ofpart.c
> +++ b/drivers/mtd/ofpart.c
> @@ -94,10 +94,10 @@ static int parse_ofpart_partitions(struct mtd_info *master,
>  
>  	if (!i) {
>  		of_node_put(pp);
> -		pr_err("No valid partition found on %s\n", node->full_name);
> +		pr_warn("No valid partition found on %s\n", node->full_name);
>  		kfree(*pparts);
>  		*pparts = NULL;
> -		return -EINVAL;
> +		return 0;
>  	}
>  
>  	return nr_parts;
> -- 
> 2.1.4
> 
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