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SubjectRe: [PATCH 0/5] mtd: core: OTP nvmem provider support
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";


>> #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.

ok

-michael

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