hwclock: implement --systz

function                                             old     new   delta
hwclock_main                                         324     434    +110
packed_usage                                       28220   28259     +39
static.hwclock_longopts                               53      60      +7
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 156/0)             Total: 156 bytes

Signed-off-by: Davide Cavalca <davide@geexbox.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 59 insertions, 24 deletions

diff --git a/include/usage.src.h b/include/usage.src.h
index 9300b3ce8..ebe80f8e1 100644
--- a/include/usage.src.h
+++ b/include/usage.src.h
@@ -1595,25 +1595,6 @@ INSERT
      "\n	-e STRING	HTML encode STRING" \
      "\n	-d STRING	URL decode STRING" \
 
-#define hwclock_trivial_usage \
-	IF_FEATURE_HWCLOCK_LONG_OPTIONS( \
-       "[-r|--show] [-s|--hctosys] [-w|--systohc]" \
-       " [-l|--localtime] [-u|--utc]" \
-       " [-f FILE]" \
-	) \
-	IF_NOT_FEATURE_HWCLOCK_LONG_OPTIONS( \
-       "[-r] [-s] [-w] [-l] [-u] [-f FILE]" \
-	)
-#define hwclock_full_usage "\n\n" \
-       "Query and set hardware clock (RTC)\n" \
-     "\nOptions:" \
-     "\n	-r	Show hardware clock time" \
-     "\n	-s	Set system time from hardware clock" \
-     "\n	-w	Set hardware clock to system time" \
-     "\n	-u	Hardware clock is in UTC" \
-     "\n	-l	Hardware clock is in local time" \
-     "\n	-f FILE	Use specified device (e.g. /dev/rtc2)" \
-
 #define id_trivial_usage \
        "[OPTIONS] [USER]"
 #define id_full_usage "\n\n" \
diff --git a/util-linux/hwclock.c b/util-linux/hwclock.c
index 922dd0578..54e97e5bb 100644
--- a/util-linux/hwclock.c
+++ b/util-linux/hwclock.c
@@ -223,12 +223,63 @@ static void from_sys_clock(const char **pp_rtcname, int utc)
 		close(rtc);
 }
 
+/*
+ * At system boot, kernel may set system time from RTC,
+ * but it knows nothing about timezones. If RTC is in local time,
+ * then system time is wrong - it is offset by timezone.
+ * This option corrects system time if RTC is in local time,
+ * and (always) sets in-kernel timezone.
+ *
+ * This is an alternate option to --hctosys that does not read the
+ * hardware clock.
+ */
+static void set_system_clock_timezone(int utc)
+{
+	struct timeval tv;
+	struct tm *broken;
+	struct timezone tz;
+
+	gettimeofday(&tv, NULL);
+	broken = localtime(&tv.tv_sec);
+	tz.tz_minuteswest = timezone / 60;
+	if (broken->tm_isdst)
+		tz.tz_minuteswest -= 60;
+	tz.tz_dsttime = 0;
+	gettimeofday(&tv, NULL);
+	if (!utc)
+		tv.tv_sec += tz.tz_minuteswest * 60;
+	if (settimeofday(&tv, &tz))
+		bb_perror_msg_and_die("settimeofday");
+}
+
+//usage:#define hwclock_trivial_usage
+//usage:	IF_FEATURE_HWCLOCK_LONG_OPTIONS(
+//usage:       "[-r|--show] [-s|--hctosys] [-w|--systohc] [-t|--systz]"
+//usage:       " [-l|--localtime] [-u|--utc]"
+//usage:       " [-f|--rtc FILE]"
+//usage:	)
+//usage:	IF_NOT_FEATURE_HWCLOCK_LONG_OPTIONS(
+//usage:       "[-r] [-s] [-w] [-t] [-l] [-u] [-f FILE]"
+//usage:	)
+//usage:#define hwclock_full_usage "\n\n"
+//usage:       "Query and set hardware clock (RTC)\n"
+//usage:     "\nOptions:"
+//usage:     "\n	-r	Show hardware clock time"
+//usage:     "\n	-s	Set system time from hardware clock"
+//usage:     "\n	-w	Set hardware clock from system time"
+//usage:     "\n	-t	Set in-kernel timezone, correct system time"
+//usage:     "\n		if hardware clock is in local time"
+//usage:     "\n	-u	Hardware clock is in UTC"
+//usage:     "\n	-l	Hardware clock is in local time"
+//usage:     "\n	-f FILE	Use specified device (e.g. /dev/rtc2)"
+
 #define HWCLOCK_OPT_LOCALTIME   0x01
 #define HWCLOCK_OPT_UTC         0x02
 #define HWCLOCK_OPT_SHOW        0x04
 #define HWCLOCK_OPT_HCTOSYS     0x08
 #define HWCLOCK_OPT_SYSTOHC     0x10
-#define HWCLOCK_OPT_RTCFILE     0x20
+#define HWCLOCK_OPT_SYSTZ       0x20
+#define HWCLOCK_OPT_RTCFILE     0x40
 
 int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int hwclock_main(int argc UNUSED_PARAM, char **argv)
@@ -239,17 +290,18 @@ int hwclock_main(int argc UNUSED_PARAM, char **argv)
 
 #if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS
 	static const char hwclock_longopts[] ALIGN1 =
-		"localtime\0" No_argument "l"
+		"localtime\0" No_argument "l" /* short opt is non-standard */
 		"utc\0"       No_argument "u"
 		"show\0"      No_argument "r"
 		"hctosys\0"   No_argument "s"
 		"systohc\0"   No_argument "w"
-		"file\0"      Required_argument "f"
+		"systz\0"     No_argument "t" /* short opt is non-standard */
+		"rtc\0"       Required_argument "f"
 		;
 	applet_long_options = hwclock_longopts;
 #endif
-	opt_complementary = "r--ws:w--rs:s--wr:l--u:u--l";
-	opt = getopt32(argv, "lurswf:", &rtcname);
+	opt_complementary = "r--wst:w--rst:s--wrt:t--rsw:l--u:u--l";
+	opt = getopt32(argv, "lurswtf:", &rtcname);
 
 	/* If -u or -l wasn't given check if we are using utc */
 	if (opt & (HWCLOCK_OPT_UTC | HWCLOCK_OPT_LOCALTIME))
@@ -261,6 +313,8 @@ int hwclock_main(int argc UNUSED_PARAM, char **argv)
 		to_sys_clock(&rtcname, utc);
 	else if (opt & HWCLOCK_OPT_SYSTOHC)
 		from_sys_clock(&rtcname, utc);
+	else if (opt & HWCLOCK_OPT_SYSTZ)
+		set_system_clock_timezone(utc);
 	else
 		/* default HWCLOCK_OPT_SHOW */
 		show_clock(&rtcname, utc);