libbb/rtc.c

   1 /*
   2  * Common RTC functions
   3  *
   4  * Licensed under GPLv2, see file LICENSE in this tarball for details.
   5  */
   6
   7 #include "libbb.h"
   8 #include "rtc_.h"
   9
  10 #if ENABLE_FEATURE_HWCLOCK_ADJTIME_FHS
  11 # define ADJTIME_PATH "/var/lib/hwclock/adjtime"
  12 #else
  13 # define ADJTIME_PATH "/etc/adjtime"
  14 #endif
  15
  16 int FAST_FUNC rtc_adjtime_is_utc(void)
  17 {
  18         int utc = 0;
  19         FILE *f = fopen_for_read(ADJTIME_PATH);
  20
  21         if (f) {
  22                 RESERVE_CONFIG_BUFFER(buffer, 128);
  23
  24                 while (fgets(buffer, sizeof(buffer), f)) {
  25                         int len = strlen(buffer);
  26
  27                         while (len && isspace(buffer[len - 1]))
  28                                 len--;
  29
  30                         buffer[len] = 0;
  31
  32                         if (strncmp(buffer, "UTC", 3) == 0) {
  33                                 utc = 1;
  34                                 break;
  35                         }
  36                 }
  37                 fclose(f);
  38
  39                 RELEASE_CONFIG_BUFFER(buffer);
  40         }
  41
  42         return utc;
  43 }
  44
  45 int FAST_FUNC rtc_xopen(const char **default_rtc, int flags)
  46 {
  47         int rtc;
  48
  49         if (!*default_rtc) {
  50                 *default_rtc = "/dev/rtc";
  51                 rtc = open(*default_rtc, flags);
  52                 if (rtc >= 0)
  53                         return rtc;
  54                 *default_rtc = "/dev/rtc0";
  55                 rtc = open(*default_rtc, flags);
  56                 if (rtc >= 0)
  57                         return rtc;
  58                 *default_rtc = "/dev/misc/rtc";
  59         }
  60
  61         return xopen(*default_rtc, flags);
  62 }
  63
  64 time_t FAST_FUNC rtc_read_time(int fd, int utc)
  65 {
  66         struct tm tm;
  67         char *oldtz = 0;
  68         time_t t = 0;
  69
  70         memset(&tm, 0, sizeof(struct tm));
  71         xioctl(fd, RTC_RD_TIME, &tm);
  72         tm.tm_isdst = -1; /* not known */
  73
  74         if (utc) {
  75                 oldtz = getenv("TZ");
  76                 putenv((char*)"TZ=UTC0");
  77                 tzset();
  78         }
  79
  80         t = mktime(&tm);
  81
  82         if (utc) {
  83                 unsetenv("TZ");
  84                 if (oldtz)
  85                         putenv(oldtz - 3);
  86                 tzset();
  87         }
  88
  89         return t;
  90 }