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

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