linux-kernel - Re: [PATCH net-next 1/4] time64.h: define PSEC_PER

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Message-ID: <5db4e640-8165-d7bf-c6b6-192ea7edfafd@arm.com>
Date:   Mon, 27 Jun 2022 08:52:51 +0100
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Vladimir Oltean <vladimir.oltean@....com>, netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Michael Walle <michael@...le.cc>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Maxim Kochetkov <fido_max@...ox.ru>,
        Colin Foster <colin.foster@...advantage.com>,
        Richie Pearn <richard.pearn@....com>,
        linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH net-next 1/4] time64.h: define PSEC_PER_NSEC and use it in
 tc-taprio

Hi Vladimir,

On 6/26/22 13:05, Vladimir Oltean wrote:
> Time-sensitive networking code needs to work with PTP times expressed in
> nanoseconds, and with packet transmission times expressed in
> picoseconds, since those would be fractional at higher than gigabit
> speed when expressed in nanoseconds.
> 
> Convert the existing uses in tc-taprio to a PSEC_PER_NSEC macro.
> 
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Vincenzo Frascino <vincenzo.frascino@....com>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---
>  include/vdso/time64.h  | 1 +
>  net/sched/sch_taprio.c | 4 ++--
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/include/vdso/time64.h b/include/vdso/time64.h
> index b40cfa2aa33c..f1c2d02474ae 100644
> --- a/include/vdso/time64.h
> +++ b/include/vdso/time64.h
> @@ -6,6 +6,7 @@
>  #define MSEC_PER_SEC	1000L
>  #define USEC_PER_MSEC	1000L
>  #define NSEC_PER_USEC	1000L
> +#define PSEC_PER_NSEC	1000L

Are you planning to use this definition in the vdso library code? If not, you
should define PSEC_PER_NSEC in "include/linux/time64.h". The vdso namespace
should contain only the definitions shared by the implementations of the kernel
and of the vdso library.

...
-- 
Regards,
Vincenzo