linux-kernel - Re: [PATCH v2 3/7] mtd: nand: add a nand.h file to expose basic NAND stuff

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Date:   Thu, 17 Nov 2016 14:14:21 +0800
From:   Peter Pan <peterpansjtu@...il.com>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     Richard Weinberger <richard@....at>, linux-mtd@...ts.infradead.org,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
        linux-kernel@...r.kernel.org,
        "peterpandong@...ron.com" <peterpandong@...ron.com>
Subject: Re: [PATCH v2 3/7] mtd: nand: add a nand.h file to expose basic NAND stuff

Hi Boris,

On Sun, Oct 16, 2016 at 10:35 PM, Boris Brezillon
<boris.brezillon@...e-electrons.com> wrote:
> Now that raw NAND header has been moved to rawnand.h, we can add a new
> nand.h file and define the common nand stuff in there.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> ---
>  include/linux/mtd/nand.h | 480 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 480 insertions(+)
>  create mode 100644 include/linux/mtd/nand.h
>
> diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
> new file mode 100644
> index 000000000000..b9b5d3c1bdf9
> --- /dev/null
> +++ b/include/linux/mtd/nand.h
[...]
> +
> +/**
> + * nand_offs_to_die - Convert an absolute offset to a die number
> + * @nand: NAND device
> + * @offs: absolute offset
> + *
> + * Returns the die number containing @offs.
> + */
> +static inline int nand_offs_to_die(struct nand_device *nand, loff_t offs)
> +{
> +       u64 die = offs;
> +
> +       do_div(die, nand->memorg.diesize);
> +
> +       return die;

Is it proper to use do_div here?. If I'm right, the divisor of do_div is 32bit.
It may cause division 0 exception when die size is larger than 4GB.
div64_u64 may be better.

Thanks,
Peter Pan