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Fix timezone offset calculations for large negative offsets

feature/test-new-mem-api
nirenjan 2017-10-27 14:19:38 -07:00
parent 46cba64e6b
commit 02c24cc964
1 changed files with 14 additions and 4 deletions
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18
lib/libx52/x52_control.c
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@ -171,6 +171,15 @@ static int libx52_write_time(libx52_device *x52, libx52_clock_id clock)
if (clock != LIBX52_CLOCK_1) { if (clock != LIBX52_CLOCK_1) {
offset = x52->timezone[clock] - x52->timezone[LIBX52_CLOCK_1]; offset = x52->timezone[clock] - x52->timezone[LIBX52_CLOCK_1];
/* Save the preliminary state, if negative, set the negative flag */
if (offset < 0) {
negative = 1;
offset = -offset;
} else {
negative = 0;
}
/* Because the packet format limits the offset from the base clock to /* Because the packet format limits the offset from the base clock to
* a maximum of +/- 1023, we can only handle a maximum offset of 17 * a maximum of +/- 1023, we can only handle a maximum offset of 17
* hours from the base clock. Eg. Honolulu and Auckland at -1000 and * hours from the base clock. Eg. Honolulu and Auckland at -1000 and
@ -180,15 +189,16 @@ static int libx52_write_time(libx52_device *x52, libx52_clock_id clock)
* exceeds +/- 1023, and subtract 1440, which will convert the offset of * exceeds +/- 1023, and subtract 1440, which will convert the offset of
* +22 to -2 hours, or +26 to +4 hours. * +22 to -2 hours, or +26 to +4 hours.
*/ */
if (offset < -1023 || offset > 1023) { while (offset > 1023) {
offset -= 1440; // Subtract 24 hours offset -= 1440; // Subtract 24 hours
} }
/* If offset is between 1024 and 1440, then we need to reverse the
* negative flag
*/
if (offset < 0) { if (offset < 0) {
negative = 1; negative = !negative;
offset = -offset; offset = -offset;
} else {
negative = 0;
} }
value = h24 << 15 | value = h24 << 15 |