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

[Cyril Hrubis]

Hi!
> 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.

This is rather broad range, are all of these really possible. Especially
the EINVAL in the set is rather troubling, since EINVAL is the most
common error returned by the Linux kernel.

> 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..9103d60 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.
> +	 */

We usually keep this verbose information in the git commit rather than
in comments in the code, since the commit message is descriptive enough
I wouldn't add this comment at all.

> +	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
> 
> 
> -- 
> Mailing list info: https://lists.linux.it/listinfo/ltp

-- 
Cyril Hrubis
chrubis@suse.cz