netdev - Re: [PATCH v2 06/29] mtd: Add support for reading MTD devices via the nvmem API

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Date:   Tue, 21 Aug 2018 13:39:16 +0200
From:   Alban <albeu@...e.fr>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     Alban Bedel <albeu@...e.fr>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Jonathan Corbet <corbet@....net>, Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Grygorii Strashko <grygorii.strashko@...com>,
        "David S . Miller" <davem@...emloft.net>,
        Naren <naren.kernel@...il.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Lukas Wunner <lukas@...ner.de>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
        Sven Van Asbroeck <svendev@...x.com>,
        Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh@...nel.org>,
        David Lechner <david@...hnology.com>,
        Andrew Lunn <andrew@...n.ch>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-i2c@...r.kernel.org, linux-mtd@...ts.infradead.org,
        linux-omap@...r.kernel.org, netdev@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v2 06/29] mtd: Add support for reading MTD devices via
 the nvmem API

On Tue, 21 Aug 2018 10:50:07 +0100
Srinivas Kandagatla <srinivas.kandagatla@...aro.org> wrote:

> Just curious...Is there a reason why we can't do it like this?:
> Is this because of issue of #address-cells and #size-cells Or mtd 
> bindings always prefer subnodes?
> 
> 	mtdnode {
> 		reg = <0x0123000 0x40000>;
> 		#address-cells = <1>;
> 		#size-cells = <1>;
> 		cell@0 {
> 			compatible = "nvmem-cell";
> 			reg = <0x0 0x14>;
> 		};
> 
> 		partitions {
> 			compatible = "fixed-partitions";
> 			#address-cells = <1>;
> 			#size-cells = <1>;
> 
> 			partition@0 {
> 				reg = <0x0 0x20000>;
> 				cell@0 {
> 					compatible = "nvmem-cell";
> 					reg = <0x0 0x10>;
> 				};
> 			};
> 		};
> 	};

That would work, the MTD partitions parser ignore child nodes with a
compatible string when looking for "old style" partitions, see [1].
However we still have the a potential address space clash between the
nvmem cells and the main device binding.

Alban

[1]: https://elixir.bootlin.com/linux/latest/source/drivers/mtd/ofpart.c#L28

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