Commit fe9f5f96 authored by Alexandre Mergnat's avatar Alexandre Mergnat Committed by Alexandre Belloni
Browse files

rtc: Fix offset calculation for .start_secs < 0 



The comparison

        rtc->start_secs > rtc->range_max

has a signed left-hand side and an unsigned right-hand side.
So the comparison might become true for negative start_secs which is
interpreted as a (possibly very large) positive value.

As a negative value can never be bigger than an unsigned value
the correct representation of the (mathematical) comparison

        rtc->start_secs > rtc->range_max

in C is:

        rtc->start_secs >= 0 && rtc->start_secs > rtc->range_max

Use that to fix the offset calculation currently used in the
rtc-mt6397 driver.

Fixes: 98951564 ("rtc: Add one offset seconds to expand RTC range")
Signed-off-by: default avatarAlexandre Mergnat <amergnat@baylibre.com>
Reviewed-by: default avatarUwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://lore.kernel.org/r/20250428-enable-rtc-v4-2-2b2f7e3f9349@baylibre.com


Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@bootlin.com>
parent 7df4cfef

drivers/rtc/class.c

+1 −1
Original line number Diff line number Diff line
@@ -326,7 +326,7 @@ static void rtc_device_get_offset(struct rtc_device *rtc) 
	 *

	 * Otherwise the offset seconds should be 0.

	 */

	if (rtc->start_secs > rtc->range_max ||

	if ((rtc->start_secs >= 0 && rtc->start_secs > rtc->range_max) ||

	    rtc->start_secs + range_secs - 1 < rtc->range_min)

		rtc->offset_secs = rtc->start_secs - rtc->range_min;

	else if (rtc->start_secs > rtc->range_min)