linux-kernel - Re: [PATCH v3 1/5] math64: New DIV_U64_ROUND

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Date:   Mon, 19 Jul 2021 15:47:07 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Pali Rohár <pali@...nel.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Vladimir Vid <vladimir.vid@...tura.hr>,
        Marek Behún <kabel@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-clk@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/5] math64: New DIV_U64_ROUND_CLOSEST helper

On Sat, Jul 17, 2021 at 3:39 PM Pali Rohár <pali@...nel.org> wrote:
>
> Provide DIV_U64_ROUND_CLOSEST helper which uses div_u64 to perform
> division rounded to the closest integer using unsigned 64bit
> dividend and unsigned 32bit divisor.

...

> +/*
> + * DIV_U64_ROUND_CLOSEST - unsigned 64bit divide with 32bit divisor rounded to nearest integer

> + * @dividend: unsigned 64bit dividend

Here you insist users to provide a u64 (or compatible) type.

> + * @divisor: unsigned 32bit divisor
> + *
> + * Divide unsigned 64bit dividend by unsigned 32bit divisor
> + * and round to closest integer.
> + *
> + * Return: dividend / divisor rounded to nearest integer
> + */
> +#define DIV_U64_ROUND_CLOSEST(dividend, divisor)       \

> +       ({ u32 _tmp = (divisor); div_u64((u64)(dividend) + _tmp / 2, _tmp); })

Here is the casting to u64. Why? (Yes, I have read v1 discussion and I
just want to continue it here).

-- 
With Best Regards,
Andy Shevchenko