netdev - Re: [PATCH] of: net: support NVMEM cells with MAC in text format

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Date:   Thu, 06 Jan 2022 10:23:22 +0100
From:   Michael Walle <michael@...le.cc>
To:     zajec5@...il.com
Cc:     andrew@...n.ch, davem@...emloft.net, devicetree@...r.kernel.org,
        hkallweit1@...il.com, kuba@...nel.org,
        linux-kernel@...r.kernel.org, linux@...linux.org.uk,
        netdev@...r.kernel.org, rafal@...ecki.pl, robh+dt@...nel.org,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: Re: [PATCH] of: net: support NVMEM cells with MAC in text format

Am 2021-12-29 13:40, schrieb Michael Walle:
>> Some NVMEM devices have text based cells. In such cases MAC is stored 
>> in
>> a XX:XX:XX:XX:XX:XX format. Use mac_pton() to parse such data and
>> support those NVMEM cells. This is required to support e.g. a very
>> popular U-Boot and its environment variables.
>> 
>> Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
>> ---
>> Please let me know if checking NVMEM cell length (6 B vs. 17 B) can be
>> considered a good enough solution. Alternatively we could use some DT
>> property to make it explicity, e.g. something like:
>> 
>> ethernet@...24000 {
>> 	compatible = "brcm,amac";
>> 	reg = <0x18024000 0x800>;
>> 
>> 	nvmem-cells = <&mac_addr>;
>> 	nvmem-cell-names = "mac-address";
>> 	nvmem-mac-format = "text";
>> };
> 
> Please note, that there is also this proposal, which had such a 
> conversion
> in mind:
> https://lore.kernel.org/linux-devicetree/20211228142549.1275412-1-michael@walle.cc/
> 
> With this patch, there are now two different places where a mac address
> format is converted. In of_get_mac_addr_nvmem() and in the imx otp 
> driver.
> And both have their shortcomings and aren't really flexible. Eg. this 
> one
> magically detects the format by comparing the length, but can't be used 
> for
> to swap bytes (because the length is also ETH_ALEN), which apparently 
> is a
> use case in the imx otp driver. And having the conversion in an nvmem
> provider device driver is still a bad thing IMHO.
> 
> I'd really like to see all these kind of transformations in one place.

Unfortunately, there were no replies yet. Can we revert this patch
until there was a discussion and before there are any users of it.
Esp. the latter is hard to track and then it might be impossible
to change them to a better solution.

Any optionions?

-michael