posix: implement the POSIX_CLOCK_SELECTION Option Group

Implement the POSIX_CLOCK_SELECTION Option Group.

This was mostly already done, but compiled / linked in the wrong places.

E.g. pthread_condattr_getclock() and pthread_condattr_setclock() were
in pthread.c and part of POSIX_THREADS_BASE. clock_nanosleep() was in
clock.c and part of POSIX_TIMERS.

This change builds them as part of clock_selection.c with
CONFIG_POSIX_CLOCK_SELECTION.

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

lib/posix/options/CMakeLists.txt

@@ -2,6 +2,7 @@
 
 set(GEN_DIR ${ZEPHYR_BINARY_DIR}/include/generated)
 
+zephyr_syscall_header_ifdef(CONFIG_POSIX_CLOCK_SELECTION posix_clock.h)
 zephyr_syscall_header_ifdef(CONFIG_POSIX_TIMERS posix_clock.h)
 zephyr_syscall_header_ifdef(CONFIG_XSI_SINGLE_PROCESS posix_clock.h)
 
@@ -45,6 +46,13 @@ if (NOT CONFIG_TC_PROVIDES_POSIX_BARRIERS)
   zephyr_library_sources_ifdef(CONFIG_POSIX_BARRIERS barrier.c)
 endif()
 
+if (NOT CONFIG_TC_PROVIDES_POSIX_CLOCK_SELECTION)
+  zephyr_library_sources_ifdef(CONFIG_POSIX_CLOCK_SELECTION
+    clock_common.c
+    clock_selection.c
+  )
+endif()
+
 if (NOT CONFIG_TC_PROVIDES_POSIX_C_LIB_EXT)
   zephyr_library_sources_ifdef(CONFIG_POSIX_C_LIB_EXT
     fnmatch.c

lib/posix/options/Kconfig.clock_selection

@@ -0,0 +1,13 @@
+# Copyright (c) 2025 Tenstorrent AI ULC
+#
+# SPDX-License-Identifier: Apache-2.0
+
+config POSIX_CLOCK_SELECTION
+	bool "POSIX Clock Selection"
+	help
+	  Select 'y' here and Zephyr will provide an implementation of the POSIX_CLOCK_SELECTION Option
+	  Group, which includes the functions clock_nanosleep(), pthread_condattr_getclock(),
+	  pthread_condattr_setclock().
+
+	  For more information, please see
+	  https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_subprofiles.html

lib/posix/options/clock_selection.c

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2023 Meta
+ * Copyright (c) 2025 Tenstorrent AI ULC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "posix_clock.h"
+#include "posix_internal.h"
+
+#include <stddef.h>
+#include <time.h>
+#include <errno.h>
+
+#include <zephyr/posix/time.h>
+#include <zephyr/toolchain.h>
+
+extern int z_clock_nanosleep(clockid_t clock_id, int flags, const struct timespec *rqtp,
+			     struct timespec *rmtp);
+
+extern int clock_nanosleep(clockid_t clock_id, int flags, const struct timespec *rqtp,
+			   struct timespec *rmtp)
+{
+	return z_clock_nanosleep(clock_id, flags, rqtp, rmtp);
+}
+
+int pthread_condattr_getclock(const pthread_condattr_t *ZRESTRICT att,
+			      clockid_t *ZRESTRICT clock_id)
+{
+	struct posix_condattr *const attr = (struct posix_condattr *)att;
+
+	if ((attr == NULL) || !attr->initialized) {
+		return EINVAL;
+	}
+
+	*clock_id = attr->clock;
+
+	return 0;
+}
+
+int pthread_condattr_setclock(pthread_condattr_t *att, clockid_t clock_id)
+{
+	struct posix_condattr *const attr = (struct posix_condattr *)att;
+
+	if (clock_id != CLOCK_REALTIME && clock_id != CLOCK_MONOTONIC) {
+		return -EINVAL;
+	}
+
+	if ((attr == NULL) || !attr->initialized) {
+		return EINVAL;
+	}
+
+	attr->clock = clock_id;
+
+	return 0;
+}

lib/posix/options/cond.c

@@ -276,36 +276,4 @@ int pthread_condattr_destroy(pthread_condattr_t *att)
 	return 0;
 }
 
-int pthread_condattr_getclock(const pthread_condattr_t *ZRESTRICT att,
-		clockid_t *ZRESTRICT clock_id)
-{
-	struct posix_condattr *const attr = (struct posix_condattr *)att;
-
-	if ((attr == NULL) || !attr->initialized) {
-		LOG_DBG("%s %s initialized", "attribute", "not");
-		return EINVAL;
-	}
-
-	*clock_id = attr->clock;
-
-	return 0;
-}
-
-int pthread_condattr_setclock(pthread_condattr_t *att, clockid_t clock_id)
-{
-	struct posix_condattr *const attr = (struct posix_condattr *)att;
-
-	if (clock_id != CLOCK_REALTIME && clock_id != CLOCK_MONOTONIC) {
-		return -EINVAL;
-	}
-
-	if ((attr == NULL) || !attr->initialized) {
-		LOG_DBG("%s %s initialized", "attribute", "not");
-		return EINVAL;
-	}
-
-	attr->clock = clock_id;
-
-	return 0;
-}
 SYS_INIT(pthread_cond_pool_init, PRE_KERNEL_1, 0);