Re: [PATCH v1] timer:clock:ptp: add support the dynamic posix clock alarm set for ptp

Richard Cochran
2019-05-07T13:49:58Z

On Sun, May 05, 2019 at 05:02:05AM +0000, Po Liu wrote:
> Current kernel code do not support the dynamic posix clock alarm set.
> This code would support it by the posix timer structure.
>
> 319 const struct k_clock clock_posix_dynamic = {
>
> 320 .clock_getres = pc_clock_getres,
> 321 .clock_set = pc_clock_settime,
> 322 .clock_get = pc_clock_gettime,
> 323 .clock_adj = pc_clock_adjtime,
> 324 + .timer_create = pc_timer_create,
> 325 + .timer_del = pc_timer_delete,
> 326 + .timer_set = pc_timer_set,
> 327 + .timer_arm = pc_timer_arm,
> }
>

Sorry, NAK, since we decided some time ago not to support timer_*
operations on dynamic clocks. You get much better application level
timer performance by synchronizing CLOCK_REALTIME to your PHC and
using clock_nanosleep() with CLOCK_REALTIME or CLOCK_MONOTONIC.

> This won't change the user space system call code. Normally the user
> space set alarm by timer_create() and timer_settime(). Reference code
> are tools/testing/selftests/ptp/testptp.c.

That program still has misleading examples. Sorry about that. I'll
submit a patch to remove them.

> +static int pc_timer_create(struct k_itimer *new_timer)
> +{
> + return 0;
> +}
> +

This of course would never work. Consider what happens when two or
more timers are created and armed.

Thanks,
Richard