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From: "Pali Rohár" <pali@kernel.org>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: "Michael Turquette" <mturquette@baylibre.com>,
	"Stephen Boyd" <sboyd@kernel.org>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Andrew Lunn" <andrew@lunn.ch>,
	"Gregory Clement" <gregory.clement@bootlin.com>,
	"Sebastian Hesselbarth" <sebastian.hesselbarth@gmail.com>,
	"Vladimir Vid" <vladimir.vid@sartura.hr>,
	"Marek Behún" <kabel@kernel.org>,
	"Geert Uytterhoeven" <geert@linux-m68k.org>,
	linux-clk@vger.kernel.org, linux-serial@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, "Willy Tarreau" <w@1wt.eu>
Subject: Re: [PATCH v3 1/5] math64: New DIV_U64_ROUND_CLOSEST helper
Date: Thu, 22 Jul 2021 23:57:43 +0200	[thread overview]
Message-ID: <20210722215743.gtwccvokecvoocmm@pali> (raw)
In-Reply-To: <CAHp75VeCC3cYu3RZPxuRN4iaM+vxp2rX+E4z+ZxzRGM8oHaMkw@mail.gmail.com>

On Monday 19 July 2021 15:47:07 Andy Shevchenko wrote:
> On Sat, Jul 17, 2021 at 3:39 PM Pali Rohár <pali@kernel.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).

See also Willy's response: https://lore.kernel.org/lkml/20210625155008.GB16901@1wt.eu/

Macro does not enforce type as opposite to function.

There is no compile time check for correct type and neither compile time
warning if smaller typed value is passed.

And e.g. passing constant with explicit ULL suffix or casting external
constant to 64bit type is impractical.

  reply	other threads:[~2021-07-22 21:57 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-24 22:48 [PATCH 00/10] serial: mvebu-uart: Fixes and new support for higher baudrates Pali Rohár
2021-06-24 22:49 ` [PATCH 01/10] serial: mvebu-uart: fix calculation of clock divisor Pali Rohár
2021-06-24 22:49 ` [PATCH 02/10] serial: mvebu-uart: do not allow changing baudrate when uartclk is not available Pali Rohár
2021-06-24 22:49 ` [PATCH 03/10] serial: mvebu-uart: correctly calculate minimal possible baudrate Pali Rohár
2021-06-24 22:49 ` [PATCH 04/10] dt-bindings: mvebu-uart: fix documentation Pali Rohár
2021-06-24 22:49 ` [PATCH 05/10] arm64: dts: marvell: armada-37xx: Fix reg for standard variant of UART Pali Rohár
2021-06-24 22:49 ` [PATCH 06/10] serial: mvebu-uart: remove unused member nb from struct mvebu_uart Pali Rohár
2021-06-24 22:49 ` [PATCH 07/10] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-06-24 22:49 ` [PATCH 08/10] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-06-24 22:49 ` [PATCH 09/10] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-06-24 22:49 ` [PATCH 10/10] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-06-25 14:36 ` [PATCH v2 00/11] serial: mvebu-uart: Fixes and new support for higher baudrates Pali Rohár
2021-06-25 14:36   ` [PATCH v2 01/11] serial: mvebu-uart: fix calculation of clock divisor Pali Rohár
2021-06-25 14:36   ` [PATCH v2 02/11] serial: mvebu-uart: do not allow changing baudrate when uartclk is not available Pali Rohár
2021-06-25 14:36   ` [PATCH v2 03/11] serial: mvebu-uart: correctly calculate minimal possible baudrate Pali Rohár
2021-06-25 14:36   ` [PATCH v2 04/11] dt-bindings: mvebu-uart: fix documentation Pali Rohár
2021-06-25 14:36   ` [PATCH v2 05/11] arm64: dts: marvell: armada-37xx: Fix reg for standard variant of UART Pali Rohár
2021-06-25 14:36   ` [PATCH v2 06/11] serial: mvebu-uart: remove unused member nb from struct mvebu_uart Pali Rohár
2021-06-25 14:36   ` [PATCH v2 07/11] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-06-25 15:22     ` Geert Uytterhoeven
2021-06-25 15:38       ` Pali Rohár
2021-06-25 15:50         ` Willy Tarreau
2021-06-25 17:39           ` Geert Uytterhoeven
2021-06-25 17:44             ` Pali Rohár
2021-06-25 18:11               ` Geert Uytterhoeven
2021-07-19 12:45         ` Andy Shevchenko
2021-06-25 14:36   ` [PATCH v2 08/11] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-06-25 14:36   ` [PATCH v2 09/11] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-06-25 14:36   ` [PATCH v2 10/11] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-06-25 14:36   ` [PATCH v2 11/11] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-07-17 12:38 ` [PATCH v3 0/5] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-07-17 12:38   ` [PATCH v3 1/5] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-07-19 12:47     ` Andy Shevchenko
2021-07-22 21:57       ` Pali Rohár [this message]
2021-07-24 11:38         ` David Laight
2021-07-17 12:38   ` [PATCH v3 2/5] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-07-17 17:26     ` Andrew Lunn
2021-07-17 18:05       ` Pali Rohár
2021-07-24  9:48         ` Pali Rohár
2021-07-24 16:33           ` Andrew Lunn
2021-07-25 12:14             ` Pali Rohár
2021-07-17 12:38   ` [PATCH v3 3/5] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-07-17 17:30     ` [PATCH v3 3/5] dt-bindings: mvebu-uart: document DT bindings for marvell, armada-3700-uart-clock Andrew Lunn
2021-08-02 14:45       ` Pali Rohár
2021-07-17 12:38   ` [PATCH v3 4/5] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-07-17 12:38   ` [PATCH v3 5/5] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-08-02 14:45 ` [PATCH v4 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-08-02 14:45   ` [PATCH v4 1/6] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-08-02 14:45   ` [PATCH v4 2/6] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-08-02 14:45   ` [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-08-06  0:30     ` Stephen Boyd
2021-08-06  8:28       ` Pali Rohár
2021-08-12 19:33         ` Stephen Boyd
2021-08-12 20:08           ` Pali Rohár
2021-08-02 14:45   ` [PATCH v4 4/6] dt-bindings: mvebu-uart: update information about UART clock Pali Rohár
2021-08-02 14:45   ` [PATCH v4 5/6] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-08-02 14:45   ` [PATCH v4 6/6] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-08-09 14:53 ` [PATCH v5 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-08-09 14:53   ` [PATCH v5 1/6] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-08-09 14:53   ` [PATCH v5 2/6] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-08-09 14:53   ` [PATCH v5 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-08-09 14:53   ` [PATCH v5 4/6] dt-bindings: mvebu-uart: update information about UART clock Pali Rohár
2021-08-09 14:53   ` [PATCH v5 5/6] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-08-09 14:53   ` [PATCH v5 6/6] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-08-20 17:22   ` [PATCH v5 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-08-31  8:35     ` Pali Rohár
2021-09-21  7:41       ` Greg Kroah-Hartman

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