kernel: POSIX: Compatibility layer for POSIX sleep APIs.

This patch provides POSIX sleep APIs for POSIX 1003.1 PSE52 standard.
sleep(n) is implemented using Zephyr k_sleep API.
uleep(n) is implemented using Zephyr k_sleep/k_busy_Wait API.

Signed-off-by: Youvedeep Singh <[email protected]>

Author: youvedeep-singh

arch/posix/include/posix_cheats.h

@@ -95,6 +95,10 @@
 #define sched_get_priority_min(...)	zap_sched_get_priority_min(__VA_ARGS__)
 #define sched_get_priority_max(...)	zap_sched_get_priority_max(__VA_ARGS__)
 
+/* Sleep */
+#define sleep(...)			zap_sleep(__VA_ARGS__)
+#define usleep(...)			zap_usleep(__VA_ARGS__)
+
 #endif /* CONFIG_ARCH_POSIX */
 
 #endif

include/posix/pthread.h

@@ -22,6 +22,7 @@ struct timespec {
 
 #include "sys/types.h"
 #include "posix_sched.h"
+#include "unistd.h"
 
 enum pthread_state {
 	/* The thread is running and joinable. */

include/posix/sys/types.h

@@ -59,6 +59,9 @@ typedef struct pthread_barrierattr {
 	int unused;
 } pthread_barrierattr_t;
 
+/* time related attributes */
+typedef unsigned long useconds_t;
+
 #endif /* CONFIG_PTHREAD_IPC */
 
 #ifdef __cplusplus

include/posix/unistd.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2018 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#ifndef __POSIX_UNISTD_H__
+#define __POSIX_UNISTD_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include_next <unistd.h>
+
+#ifdef CONFIG_PTHREAD_IPC
+#include "sys/types.h"
+
+/**
+ * @brief Sleep for a specified number of seconds.
+ *
+ * See IEEE 1003.1
+ */
+static inline int sleep(unsigned int seconds)
+{
+	k_sleep(K_SECONDS(seconds));
+	return 0;
+}
+/**
+ * @brief Suspend execution for microsecond intervals.
+ *
+ * See IEEE 1003.1
+ */
+static inline int usleep(useconds_t useconds)
+{
+	if (useconds < USEC_PER_MSEC) {
+		k_busy_wait(useconds);
+	} else {
+		k_sleep(useconds / USEC_PER_MSEC);
+	}
+
+	return 0;
+}
+
+#endif
+#ifdef __cplusplus
+}
+#endif
+#endif	/* __POSIX_UNISTD_H__ */