linux-kernel - Re: [PATCH v5 00/21] nvmem: core: introduce NVMEM layouts

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Date:   Tue, 3 Jan 2023 16:39:02 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Michael Walle <michael@...le.cc>
Cc:     Jonathan Corbet <corbet@....net>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        Dan Carpenter <error27@...il.com>
Subject: Re: [PATCH v5 00/21] nvmem: core: introduce NVMEM layouts

Hi Srinivas,

michael@...le.cc wrote on Tue,  6 Dec 2022 21:07:19 +0100:

> This is now the third attempt to fetch the MAC addresses from the VPD
> for the Kontron sl28 boards. Previous discussions can be found here:
> https://lore.kernel.org/lkml/20211228142549.1275412-1-michael@walle.cc/
> 
> 
> NVMEM cells are typically added by board code or by the devicetree. But
> as the cells get more complex, there is (valid) push back from the
> devicetree maintainers to not put that handling in the devicetree.
> 
> Therefore, introduce NVMEM layouts. They operate on the NVMEM device and
> can add cells during runtime. That way it is possible to add more complex
> cells than it is possible right now with the offset/length/bits
> description in the device tree. For example, you can have post processing
> for individual cells (think of endian swapping, or ethernet offset
> handling).
> 
> The imx-ocotp driver is the only user of the global post processing hook,
> convert it to nvmem layouts and drop the global post pocessing hook.
> 
> For now, the layouts are selected by the device tree. But the idea is
> that also board files or other drivers could set a layout. Although no
> code for that exists yet.
> 
> Thanks to Miquel, the device tree bindings are already approved and merged.
> 
> NVMEM layouts as modules?
> While possible in principle, it doesn't make any sense because the NVMEM
> core can't be compiled as a module. The layouts needs to be available at
> probe time. (That is also the reason why they get registered with
> subsys_initcall().) So if the NVMEM core would be a module, the layouts
> could be modules, too.

I believe this series still applies even though -rc1 (and -rc2) are out
now, may we know if you consider merging it anytime soon or if there
are still discrepancies in the implementation you would like to
discuss? Otherwise I would really like to see this laying in -next a
few weeks before being sent out to Linus, just in case.

Thanks,
Miquèl