Re: [PATCH net-next 1/4] time64.h: define PSEC_PER_NSEC and use it in tc-taprio

Hi Vladimir,

On 6/27/22 09:51, Vladimir Oltean wrote:

Hi Vincenzo,

On Mon, Jun 27, 2022 at 08:52:51AM +0100, Vincenzo Frascino wrote:

quoted

Hi Vladimir,

On 6/26/22 13:05, Vladimir Oltean wrote:

quoted

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@kernel.org>
Cc: Thomas Gleixner <redacted>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.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.

I am not. I thought it would be ok to preserve the locality of
definitions by placing this near the others of its kind, since a macro
doesn't affect the compiled vDSO code in any way. But if you prefer, I
can create a new mini-section in linux/time64.h. Any preference on where
exactly to place that definition within the file?

I do not have a strong opinion on where to put it. But I think that if you put a
section above TIME64_MAX should work.

-- 
Regards,
Vincenzo