[PATCH] RTC subsystem: class
Add the basic RTC subsystem infrastructure to the kernel.
rtc/class.c - registration facilities for RTC drivers
rtc/interface.c - kernel/rtc interface functions
rtc/hctosys.c - snippet of code that copies hw clock to sw clock
at bootup, if configured to do so.
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/rtc/hctosys.c b/drivers/rtc/hctosys.c
new file mode 100644
index 0000000..d02fe9a
--- /dev/null
+++ b/drivers/rtc/hctosys.c
@@ -0,0 +1,69 @@
+/*
+ * RTC subsystem, initialize system time on startup
+ *
+ * Copyright (C) 2005 Tower Technologies
+ * Author: Alessandro Zummo <a.zummo@towertech.it>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+*/
+
+#include <linux/rtc.h>
+
+/* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
+ * whether it stores the most close value or the value with partial
+ * seconds truncated. However, it is important that we use it to store
+ * the truncated value. This is because otherwise it is necessary,
+ * in an rtc sync function, to read both xtime.tv_sec and
+ * xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
+ * of >32bits is not possible. So storing the most close value would
+ * slow down the sync API. So here we have the truncated value and
+ * the best guess is to add 0.5s.
+ */
+
+static int __init rtc_hctosys(void)
+{
+ int err;
+ struct rtc_time tm;
+ struct class_device *class_dev = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);
+
+ if (class_dev == NULL) {
+ printk("%s: unable to open rtc device (%s)\n",
+ __FILE__, CONFIG_RTC_HCTOSYS_DEVICE);
+ return -ENODEV;
+ }
+
+ err = rtc_read_time(class_dev, &tm);
+ if (err == 0) {
+ err = rtc_valid_tm(&tm);
+ if (err == 0) {
+ struct timespec tv;
+
+ tv.tv_nsec = NSEC_PER_SEC >> 1;
+
+ rtc_tm_to_time(&tm, &tv.tv_sec);
+
+ do_settimeofday(&tv);
+
+ dev_info(class_dev->dev,
+ "setting the system clock to "
+ "%d-%02d-%02d %02d:%02d:%02d (%u)\n",
+ tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
+ tm.tm_hour, tm.tm_min, tm.tm_sec,
+ (unsigned int) tv.tv_sec);
+ }
+ else
+ dev_err(class_dev->dev,
+ "hctosys: invalid date/time\n");
+ }
+ else
+ dev_err(class_dev->dev,
+ "hctosys: unable to read the hardware clock\n");
+
+ rtc_class_close(class_dev);
+
+ return 0;
+}
+
+late_initcall(rtc_hctosys);
