From 577cf09bc5aed36b40a3dcaf3842e8c35b6a8dcc Mon Sep 17 00:00:00 2001
From: Ahmad Fatoum <a.fatoum@pengutronix.de>
Date: Wed, 17 Jul 2024 13:00:39 +0200
Subject: [PATCH] rtc: factor out RTC_Linux_ReadTime_AfterInterrupt

We have code to read time after an RTC's UIE interrupt, which we
currently use as part of maintaining the correction file.

In a later commit, we will need the same functionality for using the RTC
as reference clock, so export the function and give it a descriptive
name appropriate for a globally visible function.
---
 rtc_linux.c | 52 +++++++++++++++++++++++++++++++---------------------
 rtc_linux.h |  2 ++
 2 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/rtc_linux.c b/rtc_linux.c
index 4de11b0..4c98cb9 100644
--- a/rtc_linux.c
+++ b/rtc_linux.c
@@ -785,43 +785,53 @@ RTC_Linux_CheckInterrupt(int fd)
   return (data & RTC_UF) == RTC_UF;
 }
 
+time_t
+RTC_Linux_ReadTime_AfterInterrupt(int fd, int utc, struct timespec *sys_time_cooked)
+{
+  int status;
+  struct rtc_time rtc_raw;
+
+  /* Read RTC time, sandwiched between two polls of the system clock
+     so we can bound any error. */
+
+  SCH_GetLastEventTime(sys_time_cooked, NULL, NULL);
+
+  status = ioctl(fd, RTC_RD_TIME, &rtc_raw);
+  if (status < 0) {
+    LOG(LOGS_ERR, "Could not read time from %s : %s", CNF_GetRtcDevice(), strerror(errno));
+    return -1;
+  }
+
+  /* Convert RTC time into a struct timespec */
+  return t_from_rtc(&rtc_raw, utc);
+}
+
 static void
 read_from_device(int fd_, int event, void *any)
 {
   int status;
   struct timespec sys_time;
-  struct rtc_time rtc_raw;
   time_t rtc_t;
   int error = 0;
 
   status = RTC_Linux_CheckInterrupt(fd);
-  if (status < 0) {
-    SCH_RemoveFileHandler(fd);
-    RTC_Linux_SwitchInterrupt(fd, 0); /* Likely to raise error too, but just to be sure... */
-    close(fd);
-    fd = -1;
-    return;
+  if (status == -1) {
+      SCH_RemoveFileHandler(fd);
+      RTC_Linux_SwitchInterrupt(fd, 0); /* Likely to raise error too, but just to be sure... */
+      close(fd);
+      fd = -1;
+      return;
   } else if (status == 0) {
-    return;
+      /* Wait for the next interrupt, this one may be bogus */
+      return;
   }
 
-  SCH_GetLastEventTime(&sys_time, NULL, NULL);
-
-  status = ioctl(fd, RTC_RD_TIME, &rtc_raw);
-  if (status < 0) {
-    LOG(LOGS_ERR, "Could not read time from %s : %s", CNF_GetRtcDevice(), strerror(errno));
+  rtc_t = RTC_Linux_ReadTime_AfterInterrupt(fd, rtc_on_utc, &sys_time);
+  if (rtc_t == (time_t)-1) {
     error = 1;
     goto turn_off_interrupt;
   }
 
-  /* Convert RTC time into a struct timespec */
-  rtc_t = t_from_rtc(&rtc_raw, rtc_on_utc);
-
-  if (rtc_t == (time_t)(-1)) {
-    error = 1;
-    goto turn_off_interrupt;
-  }      
-
   process_reading(rtc_t, &sys_time);
 
   if (n_samples < 4) {
diff --git a/rtc_linux.h b/rtc_linux.h
index 1f67ba8..350fd50 100644
--- a/rtc_linux.h
+++ b/rtc_linux.h
@@ -44,5 +44,7 @@ extern void RTC_Linux_CycleLogFile(void);
 
 extern int RTC_Linux_SwitchInterrupt(int fd, int on_off);
 extern int RTC_Linux_CheckInterrupt(int fd);
+extern time_t RTC_Linux_ReadTime_AfterInterrupt(int fd, int utc,
+                                                struct timespec *sys_time_cooked);
 
 #endif /* _GOT_RTC_LINUX_H */