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

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Message-ID: <20210420140801.GA3240688@robh.at.kernel.org>
Date:   Tue, 20 Apr 2021 09:08:01 -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 09:26:03PM +0200, Michael Walle wrote:
> Hi Rob,
> 
> Am 2021-04-16 20:44, schrieb Rob Herring:
> > 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?
> 
> There are two different compatibles: "mtd-user-otp" and "mtd-factory-otp"
> to differentiate what kind of OTP should be used (and both are possible
> at the same time). Thus nvmem-cells alone won't be enough. We could drop
> the "mtd-" prefix though.
> 
> Is there a benefit of having the following?
>   compatible = "user-otp", "nvmem-cells";

Yes. I assume 'user-otp' tells you something about the region and 
'nvmem-cells' tells you that there are child nodes of nvmem data. Of 
course 'user-otp' could imply 'nvmem-cells' as you did. I'm fine with 
either way.

Rob