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

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Date:   Tue, 28 Aug 2018 11:20:31 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Alban <albeu@...e.fr>,
        Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     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,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v2 06/29] mtd: Add support for reading MTD devices via the
 nvmem API



On 23/08/18 11:29, Alban wrote:
> Let say I have a device that use the following binding:
> 
> device {
>      compatible = "example-device";
>      #address-cells = <2>;
>      #size-cells = <1>;
> 
>      child@0,0 {
>          reg = <0x0 0x0>;
>          ...
>      };
> 
>      child@1,2 {
>          reg = <0x1 0x2>;
>          ...
>      };
> 
> };
> 
> Now this binding already use the node address space for something,
> so putting a nvmem node as direct child would not work.

AFAIK, It should work but the we would get a DT warning this, as nvmem 
does not use of_address based apis to parse this. Which should be 
totally fixed!!

As discussed before once we add support to #address-cells and 
#size-cells in nvmem core this should not be a problem.


--srini
  Here it is
> quiet clear as we have 2 address cells, however even if the number of
> cells and the cells size would match it would still be conceptually
> wrong as both bindings then use the same address space for something
> different.