[LTP] [PATCH] rtc02: skip (TCONF) on read-only RTCs that reject RTC_SET_TIME

[Kuba Pawlak]

Some RTC hardware does not allow setting the time from the host. For
example Qualcomm PMIC RTCs (rtc-pm8xxx) that are configured without the
allow-set-time DT property and without an nvmem/UEFI offset return
-ENODEV from RTC_SET_TIME; the counter free-runs from the epoch and is
only usable as an uptime source. On such devices rtc02 currently reports
TFAIL, which is a hardware limitation rather than a kernel defect.

Probe whether the RTC can be set in the setup phase, writing back the
value just read so a writable RTC is left unchanged. When RTC_SET_TIME
fails with an errno that indicates the operation is unsupported or not
permitted (ENODEV, EOPNOTSUPP, EINVAL, EACCES, EPERM), skip the whole
test with TCONF.

Doing the check in setup, before tst_rtc_clock_save(), also avoids the
cleanup path (tst_rtc_clock_restore()) issuing RTC_SET_TIME and turning
the run into a TBROK on such devices. If the probe succeeds the test body
runs as before, so no additional handling is needed there.

Signed-off-by: Kuba Pawlak <kuba.pawlak@canonical.com>
---
 testcases/kernel/device-drivers/rtc/rtc02.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/testcases/kernel/device-drivers/rtc/rtc02.c b/testcases/kernel/device-drivers/rtc/rtc02.c
index 34509ab..042fa65 100644
--- a/testcases/kernel/device-drivers/rtc/rtc02.c
+++ b/testcases/kernel/device-drivers/rtc/rtc02.c
@@ -16,6 +16,7 @@
  */
 
 #include <stdio.h>
+#include <errno.h>
 #include "tst_rtctime.h"
 #include "tst_wallclock.h"
 #include "tst_test.h"
@@ -133,10 +134,29 @@ static void set_rtc_test(void)
 static void rtc_setup(void)
 {
 	int exists = access(rtc_dev, F_OK);
+	struct rtc_time probe_tm;
 
 	if (exists < 0)
 		tst_brk(TCONF, "RTC device %s not available", rtc_dev);
 
+	/*
+	 * Skip on RTCs that do not allow setting the time, e.g. Qualcomm PMIC
+	 * RTCs without allow-set-time or an nvmem offset, where RTC_SET_TIME
+	 * returns -ENODEV. Probe with the current time so a writable RTC is
+	 * left unchanged, and skip here (before tst_rtc_clock_save()) so the
+	 * cleanup restore does not fail on such devices.
+	 */
+	if (tst_rtc_gettime(rtc_dev, &probe_tm))
+		tst_brk(TBROK | TERRNO, "ioctl() RTC_RD_TIME");
+	if (tst_rtc_settime(rtc_dev, &probe_tm)) {
+		if (errno == ENODEV || errno == EOPNOTSUPP ||
+		    errno == EINVAL || errno == EACCES || errno == EPERM)
+			tst_brk(TCONF | TERRNO,
+				"RTC does not support setting the time");
+
+        tst_brk(TBROK | TERRNO, "ioctl() RTC_SET_TIME");
+	}
+
 	tst_rtc_clock_save(rtc_dev);
 }
 
-- 
2.43.0