posix: provide timespec_to_clock_timeoutms

Provide a private internal function timespec_to_clock_timeoutms() to
complement timespec_to_timeoutms(). This new variant accepts a clock_t
parameter that allows the caller to specify which clock to use.

The original timespec_to_timeoutms() then just becomes a static inline
wrapper around the original.

Note: timespec_to_clock_timeoutms() and timespec_to_timeoutms() might
have a limited lifespan, since it might make sense to create a
common timespec manipulation library.

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>

Author: cfriedt

lib/posix/options/posix_clock.h

@@ -11,6 +11,7 @@
 #include <stdint.h>
 #include <time.h>
 
+uint32_t timespec_to_clock_timeoutms(clockid_t clock_id, const struct timespec *abstime);
 uint32_t timespec_to_timeoutms(const struct timespec *abstime);
 
 __syscall int __posix_clock_get_base(clockid_t clock_id, struct timespec *ts);

lib/posix/options/timespec_to_timeout.c

@@ -10,16 +10,12 @@
 #include <ksched.h>
 #include <zephyr/posix/time.h>
 
-uint32_t timespec_to_timeoutms(const struct timespec *abstime)
+uint32_t timespec_to_clock_timeoutms(clockid_t clock_id, const struct timespec *abstime)
 {
 	int64_t milli_secs, secs, nsecs;
 	struct timespec curtime;
 
-	/* FIXME: Zephyr does have CLOCK_REALTIME to get time.
-	 * As per POSIX standard time should be calculated wrt CLOCK_REALTIME.
-	 * Zephyr deviates from POSIX 1003.1 standard on this aspect.
-	 */
-	clock_gettime(CLOCK_MONOTONIC, &curtime);
+	clock_gettime(clock_id, &curtime);
 	secs = abstime->tv_sec - curtime.tv_sec;
 	nsecs = abstime->tv_nsec - curtime.tv_nsec;
 
@@ -31,3 +27,8 @@ uint32_t timespec_to_timeoutms(const struct timespec *abstime)
 
 	return milli_secs;
 }
+
+uint32_t timespec_to_timeoutms(const struct timespec *abstime)
+{
+	return timespec_to_clock_timeoutms(CLOCK_MONOTONIC, abstime);
+}