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

From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
To: Miquel Raynal <miquel.raynal@bootlin.com>,
	Michael Walle <michael@walle.cc>
Cc: Jonathan Corbet <corbet@lwn.net>,
	Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
	Dan Carpenter <error27@gmail.com>
Subject: Re: [PATCH v5 00/21] nvmem: core: introduce NVMEM layouts
Date: Tue, 3 Jan 2023 15:51:31 +0000	[thread overview]
Message-ID: <cf00e248-1f2c-d4ce-868d-9f77b2c9b76f@linaro.org> (raw)
In-Reply-To: <20230103163902.218cb5c7@xps-13>

Hi Miquel,

On 03/01/2023 15:39, Miquel Raynal wrote:
> Hi Srinivas,
> 
> michael@walle.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 for the work!

Lets get some testing in -next.

Applied now,

--srini
> 
> Thanks,
> Miquèl

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