selftests/timers: Add set-tai from the timetest suite

This patch adds the set-tai test which ensures the tai offset
can be set properly from adjtimex.

Cc: Shuah Khan <[e-mail]>
Cc: Prarit Bhargava <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Richard Cochran <[e-mail]>
Signed-off-by: John Stultz <[e-mail]>
Tested-by: Prarit Bhargava <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/timers/Makefile

···
 bins = posix_timers nanosleep inconsistency-check nsleep-lat raw_skew \
 	set-timer-lat threadtest mqueue-lat valid-adjtimex \
 	alarmtimer-suspend change_skew skew_consistency clocksource-switch \
-	leap-a-day leapcrash
+	leap-a-day leapcrash set-tai
 
 all: ${bins}
 
···
 	./clocksource-switch
 	./leap-a-day -s -i 10
 	./leapcrash
+	./set-tai
 
 clean:
 	rm -f ${bins}

tools/testing/selftests/timers/set-tai.c

···
+/* Set tai offset
+ *              by: John Stultz <[e-mail]>
+ *              (C) Copyright Linaro 2013
+ *              Licensed under the GPLv2
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <sys/time.h>
+#include <sys/timex.h>
+#include <string.h>
+#include <signal.h>
+#include <unistd.h>
+#ifdef KTEST
+#include "../kselftest.h"
+#else
+static inline int ksft_exit_pass(void)
+{
+	exit(0);
+}
+static inline int ksft_exit_fail(void)
+{
+	exit(1);
+}
+#endif
+
+int set_tai(int offset)
+{
+	struct timex tx;
+
+	memset(&tx, 0, sizeof(tx));
+
+	tx.modes = ADJ_TAI;
+	tx.constant = offset;
+
+	return adjtimex(&tx);
+}
+
+int get_tai(void)
+{
+	struct timex tx;
+
+	memset(&tx, 0, sizeof(tx));
+
+	adjtimex(&tx);
+	return tx.tai;
+}
+
+int main(int argc, char **argv)
+{
+	int i, ret;
+
+	ret = get_tai();
+	printf("tai offset started at %i\n", ret);
+
+	printf("Checking tai offsets can be properly set: ");
+	for (i = 1; i <= 60; i++) {
+		ret = set_tai(i);
+		ret = get_tai();
+		if (ret != i) {
+			printf("[FAILED] expected: %i got %i\n", i, ret);
+			return ksft_exit_fail();
+		}
+	}
+	printf("[OK]\n");
+	return ksft_exit_pass();
+}