linux-kernel - Re: [RFC PATCH 6/6] block: implement NVMEM provider

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Message-ID: <ZLonS7QXLj2lg4Zg@infradead.org>
Date:   Thu, 20 Jul 2023 23:35:55 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Daniel Golle <daniel@...rotopia.org>
Cc:     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 6/6] block: implement NVMEM provider

> +static int blk_nvmem_reg_read(void *priv, unsigned int from,
> +			      void *val, size_t bytes)
> +{
> +	pgoff_t f_index = from >> PAGE_SHIFT;
> +	struct address_space *mapping;
> +	struct blk_nvmem *bnv = priv;
> +	size_t bytes_left = bytes;
> +	struct folio *folio;
> +	unsigned long offs, to_read;
> +	void *p;

Btw, this function really should be using kern_read on a file
using filp_open instead of poking into block device internals.
That way you can even have a generic file provider that works
on anything that can be read from.