110 lines
2.0 KiB
C
110 lines
2.0 KiB
C
/*
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* Common RTC functions
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*
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* Licensed under GPLv2, see file LICENSE in this source tree.
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*/
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#include "libbb.h"
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#include "rtc_.h"
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int FAST_FUNC rtc_adjtime_is_utc(void)
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{
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int utc = 0;
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FILE *f = fopen_for_read(ADJTIME_PATH);
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if (f) {
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char buffer[128];
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while (fgets(buffer, sizeof(buffer), f)) {
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if (is_prefixed_with(buffer, "UTC")) {
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utc = 1;
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break;
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}
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}
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fclose(f);
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}
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return utc;
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}
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/* rtc opens are exclusive.
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* Try to run two "hwclock -w" at the same time to see it.
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* Users wouldn't expect that to fail merely because /dev/rtc
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* was momentarily busy, let's try a bit harder on errno == EBUSY.
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*/
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static int open_loop_on_busy(const char *name, int flags)
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{
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int rtc;
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/*
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* Tested with two parallel "hwclock -w" loops.
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* With try = 10, no failures with 2x1000000 loop iterations.
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*/
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int try = 1000 / 20;
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again:
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errno = 0;
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rtc = open(name, flags);
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if (errno == EBUSY) {
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usleep(20 * 1000);
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if (--try != 0)
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goto again;
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/* EBUSY. Last try, exit on error instead of returning -1 */
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return xopen(name, flags);
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}
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return rtc;
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}
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/* Never fails */
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int FAST_FUNC rtc_xopen(const char **default_rtc, int flags)
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{
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int rtc;
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const char *name =
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"/dev/rtc""\0"
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"/dev/rtc0""\0"
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"/dev/misc/rtc""\0";
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if (!*default_rtc)
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goto try_name;
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name = ""; /*else: we have rtc name, don't try other names */
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for (;;) {
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rtc = open_loop_on_busy(*default_rtc, flags);
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if (rtc >= 0)
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return rtc;
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if (!name[0])
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return xopen(*default_rtc, flags);
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try_name:
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*default_rtc = name;
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name += strlen(name) + 1;
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}
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}
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void FAST_FUNC rtc_read_tm(struct tm *ptm, int fd)
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{
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memset(ptm, 0, sizeof(*ptm));
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xioctl(fd, RTC_RD_TIME, ptm);
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ptm->tm_isdst = -1; /* "not known" */
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}
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time_t FAST_FUNC rtc_tm2time(struct tm *ptm, int utc)
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{
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char *oldtz = oldtz; /* for compiler */
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time_t t;
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if (utc) {
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oldtz = getenv("TZ");
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putenv((char*)"TZ=UTC0");
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tzset();
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}
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t = mktime(ptm);
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if (utc) {
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unsetenv("TZ");
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if (oldtz)
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putenv(oldtz - 3);
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tzset();
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}
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return t;
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}
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