hwclock: add a new --compare option

The new option imitates adjtimex -c functionality and outputs
the drift in 10 second intervals.

[kzak@redhat.com: - coding style
                  - print hw and system time columns too]

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/sys-utils/hwclock.c b/sys-utils/hwclock.c
index e25546d252cbaea8f5cc00e5e3319f83cb8a7b1b..5a4c87e288aa9a58f0225da25b30b0a31eef3b4e 100644 (file)
--- a/sys-utils/hwclock.c
+++ b/sys-utils/hwclock.c
@@ -1337,6 +1337,66 @@ manipulate_epoch(const bool getepoch,
 # endif                /* __alpha__ */
 #endif         /* __linux__ */
 
+/*
+ * Compare the system and CMOS time and output the drift
+ * in 10 second intervals.
+ */
+static int compare_clock (const bool utc, const bool local_opt)
+{
+       struct tm tm;
+       struct timeval tv;
+       struct adjtime adjtime;
+       double time1_sys, time2_sys;
+       time_t time1_hw, time2_hw;
+       bool hclock_valid = FALSE, universal, first_pass = TRUE;
+       int rc;
+
+       /* dummy call for increased precision */
+       gettimeofday(&tv, NULL);
+
+       rc = read_adjtime(&adjtime);
+       if (rc)
+               return rc;
+
+       universal = hw_clock_is_utc(utc, local_opt, adjtime);
+
+       synchronize_to_clock_tick();
+       ur->read_hardware_clock(&tm);
+
+       gettimeofday(&tv, NULL);
+       time1_sys = tv.tv_sec + tv.tv_usec / 1000000.0;
+
+       mktime_tz(tm, universal, &hclock_valid, &time1_hw);
+
+       while (1) {
+               double res;
+
+               synchronize_to_clock_tick();
+               ur->read_hardware_clock(&tm);
+
+               gettimeofday(&tv, NULL);
+               time2_sys = tv.tv_sec + tv.tv_usec / 1000000.0;
+
+               mktime_tz(tm, universal, &hclock_valid, &time2_hw);
+
+               res = (((double) time1_hw - time1_sys) -
+                      ((double) time2_hw - time2_sys))
+                     / (double) (time2_hw - time1_hw);
+
+               if (!first_pass)
+                       printf("%10.0f   %10.6f   %15.0f   %4.0f\n",
+                               (double) time2_hw, time2_sys, res * 1e6, res *1e4);
+               else {
+                       first_pass = FALSE;
+                       printf("hw-time      system-time         freq-offset-ppm   tick\n");
+                       printf("%10.0f   %10.6f\n", (double) time1_hw, time1_sys);
+               }
+               sleep(10);
+       }
+
+       return 0;
+}
+
 static void out_version(void)
 {
        printf(_("%s from %s\n"), program_invocation_short_name, PACKAGE_STRING);
@@ -1370,7 +1430,8 @@ static void usage(const char *fmt, ...)
                " -w, --systohc        set the hardware clock from the current system time\n"
                "     --systz          set the system time based on the current timezone\n"
                "     --adjust         adjust the RTC to account for systematic drift since\n"
-               "                        the clock was last set or adjusted\n"), usageto);
+               "                        the clock was last set or adjusted\n"
+               " -c  --compare        periodically compare the system clock with the CMOS clock\n"), usageto);
 #ifdef __linux__
        fputs(_("     --getepoch       print out the kernel's hardware clock epoch value\n"
                "     --setepoch       set the kernel's hardware clock epoch value to the \n"
@@ -1438,7 +1499,7 @@ int main(int argc, char **argv)
        /* Variables set by various options; show may also be set later */
        /* The options debug, badyear and epoch_option are global */
        bool show, set, systohc, hctosys, systz, adjust, getepoch, setepoch,
-           predict;
+           predict, compare;
        bool utc, testing, local_opt, noadjfile, directisa;
        char *date_opt;
 #ifdef __alpha__
@@ -1463,6 +1524,7 @@ int main(int argc, char **argv)
 
        static const struct option longopts[] = {
                {"adjust",      0, 0, 'a'},
+               {"compare",     0, 0, 'c'},
                {"help",        0, 0, 'h'},
                {"show",        0, 0, 'r'},
                {"hctosys",     0, 0, 's'},
@@ -1540,7 +1602,7 @@ int main(int argc, char **argv)
 
        /* Set option defaults */
        show = set = systohc = hctosys = systz = adjust = noadjfile = predict =
-           FALSE;
+           compare = FALSE;
        getepoch = setepoch = utc = local_opt = directisa = testing = debug = FALSE;
 #ifdef __alpha__
        ARCconsole = Jensen = SRM = funky_toy = badyear = FALSE;
@@ -1548,7 +1610,7 @@ int main(int argc, char **argv)
        date_opt = NULL;
 
        while ((c = getopt_long(argc, argv,
-                               "?hvVDarsuwAJSFf:", longopts, NULL)) != -1) {
+                               "?hvVDacrsuwAJSFf:", longopts, NULL)) != -1) {
 
                err_exclusive_options(c, longopts, excl, excl_st);
 
@@ -1559,6 +1621,9 @@ int main(int argc, char **argv)
                case 'a':
                        adjust = TRUE;
                        break;
+               case 'c':
+                       compare = TRUE;
+                       break;
                case 'r':
                        show = TRUE;
                        break;
@@ -1733,9 +1798,16 @@ int main(int argc, char **argv)
                }
        }
 
-       rc = manipulate_clock(show, adjust, noadjfile, set, set_time,
+       if (compare) {
+               if (compare_clock(utc, local_opt))
+                       hwclock_exit(EX_NOPERM);
+
+               rc = EX_OK;
+       } else
+               rc = manipulate_clock(show, adjust, noadjfile, set, set_time,
                              hctosys, systohc, systz, startup_time, utc,
                              local_opt, testing, predict);
+
        hwclock_exit(rc);
        return rc;              /* Not reached */
 }