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

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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@xxxxxxxxxx>
---
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@18024000 {
	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@xxxxxxxx/

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



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