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Date:   Thu, 20 Jul 2023 08:30:39 -0700
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Subject: Re: [RFC PATCH 0/6] nvmem: add block device NVMEM provider
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To:     Daniel Golle <daniel@makrotopia.org>, Jens Axboe <axboe@kernel.dk>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Dave Chinner <dchinner@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        =?UTF-8?Q?Thomas_Wei=c3=9fschuh?= <linux@weissschuh.net>,
        Jan Kara <jack@suse.cz>, Damien Le Moal <dlemoal@kernel.org>,
        Ming Lei <ming.lei@redhat.com>, Min Li <min15.li@samsung.com>,
        Christian Loehle <CLoehle@hyperstone.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Hannes Reinecke <hare@suse.de>,
        Jack Wang <jinpu.wang@ionos.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Yeqi Fu <asuk4.q@gmail.com>, Avri Altman <avri.altman@wdc.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Ye Bin <yebin10@huawei.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= <rafal@milecki.pl>,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mmc@vger.kernel.org, linux-mtd@lists.infradead.org
References: <cover.1689802933.git.daniel@makrotopia.org>
From:   Bart Van Assche <bvanassche@acm.org>
In-Reply-To: <cover.1689802933.git.daniel@makrotopia.org>
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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.