linux-kernel - Re: [PATCH 0/5] mtd: core: OTP nvmem provider support

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Date:   Fri, 16 Apr 2021 13:44:23 -0500
From:   Rob Herring <robh@...nel.org>
To:     Michael Walle <michael@...le.cc>
Cc:     linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: Re: [PATCH 0/5] mtd: core: OTP nvmem provider support

On Fri, Apr 16, 2021 at 01:49:23PM +0200, Michael Walle wrote:
> The goal is to fetch a (base) MAC address from the OTP region of a SPI NOR
> flash.
> 
> This is the first part, where I try to add the nvmem provider support to
> the MTD core.
> 
> I'm not sure about the device tree bindings. Consider the following two
> variants:
> 
> (1)
>     flash@0 {
>         ..
> 
>         otp {
>             compatible = "mtd-user-otp";

mtd is a linuxism. Why not just 'nvmem-cells' here or as a fallback if 
we come up with a better name? 

>             #address-cells = <1>;
>             #size-cells = <1>;
> 
>             serial-number@0 {
>                 reg = <0x0 0x8>;
>             };
>         };
>     };
> 
> (2)
>     flash@0 {
>         ..
> 
>         otp {
>             compatible = "mtd-user-otp";
>             #address-cells = <1>;
>             #size-cells = <1>;
> 
> 			some-useful-name {
>                 compatible = "nvmem-cells";
> 
>                 serial-number@0 {
>                     reg = <0x0 0x8>;
>                 };
> 			};
>         };
>     };
> 
> Both bindings use a subnode "opt[-N]". We cannot have the nvmem cells as
> children to the flash node because of the legacy partition binding.
> 
> (1) seems to be the form which is used almost everywhere in the kernel.
> That is, the nvmem cells are just children of the parent node.
> 
> (2) seem to be more natural, because there might also be other properties
> inside the otp subnode and might be more future-proof.
> 
> At the moment this patch implements (1).

I think approach (1) seems fine.

Rob