linux-kernel - Re: [RFC PATCH 0/6] nvmem: add block device NVMEM provider

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Message-ID: <352167df-34fc-ddff-def9-902873796536@acm.org>
Date:   Thu, 20 Jul 2023 08:30:39 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Daniel Golle <daniel@...rotopia.org>, Jens Axboe <axboe@...nel.dk>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Dave Chinner <dchinner@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Thomas Weißschuh <linux@...ssschuh.net>,
        Jan Kara <jack@...e.cz>, Damien Le Moal <dlemoal@...nel.org>,
        Ming Lei <ming.lei@...hat.com>, Min Li <min15.li@...sung.com>,
        Christian Loehle <CLoehle@...erstone.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Hannes Reinecke <hare@...e.de>,
        Jack Wang <jinpu.wang@...os.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Yeqi Fu <asuk4.q@...il.com>, Avri Altman <avri.altman@....com>,
        Hans de Goede <hdegoede@...hat.com>,
        Ye Bin <yebin10@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rafał Miłecki <rafal@...ecki.pl>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mmc@...r.kernel.org, linux-mtd@...ts.infradead.org
Subject: Re: [RFC PATCH 0/6] nvmem: add block device NVMEM provider

On 7/19/23 15:01, Daniel Golle wrote:
> On embedded devices using an eMMC it is common that one or more (hw/sw)
> partitions on the eMMC are used to store MAC addresses and Wi-Fi
> calibration EEPROM data.
> 
> Implement an NVMEM provider backed by block devices as typically the
> NVMEM framework is used to have kernel drivers read and use binary data
> from EEPROMs, efuses, flash memory (MTD), ...
> 
> In order to be able to reference hardware partitions on an eMMC, add code
> to bind each hardware partition to a specific firmware subnode.
> 
> This series is meant to open the discussion on how exactly the device tree
> schema for block devices and partitions may look like, and even if using
> the block layer to back the NVMEM device is at all the way to go -- to me
> it seemed to be a good solution because it will be reuable e.g. for NVMe.

Is my understanding correct that these devices boot from eMMC and not over
Wi-Fi? If so, why does this calibration data have to be stored on a raw
block device? Why can't this information be loaded from a file on a
filesystem?

Thanks,

Bart.