[patch V2 3/3] ptp: Enable auxiliary clocks for PTP_SYS_OFFSET_EXTENDED

[Thomas Gleixner <tglx@linutronix.de>]

Allow ioctl(PTP_SYS_OFFSET_EXTENDED*) to select CLOCK_AUX clock ids for
generating the pre and post hardware readout timestamps.

Aside of adding these clocks to the clock ID validation, this also requires
to check the timestamp to be valid, i.e. the seconds value being greater
than or equal zero. This is necessary because AUX clocks can be
asynchronously enabled or disabled, so there is no way to validate the
availability upfront.

The same could have been achieved by handing the return value of
ktime_get_aux_ts64() all the way down to the IOCTL call site, but that'd
require to modify all existing ptp::gettimex64() callbacks and their inner
call chains. The timestamp check achieves the same with less churn and less
complicated code all over the place.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
---
V2: Catch CONFIG_POSIX_AUX_CLOCKS=n right at the clockid check
---
 drivers/ptp/ptp_chardev.c |   24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -325,13 +325,22 @@ static long ptp_sys_offset_extended(stru
 	if (IS_ERR(extoff))
 		return PTR_ERR(extoff);
 
-	if (extoff->n_samples > PTP_MAX_SAMPLES ||
-	    extoff->rsv[0] || extoff->rsv[1] ||
-	    (extoff->clockid != CLOCK_REALTIME &&
-	     extoff->clockid != CLOCK_MONOTONIC &&
-	     extoff->clockid != CLOCK_MONOTONIC_RAW))
+	if (extoff->n_samples > PTP_MAX_SAMPLES || extoff->rsv[0] || extoff->rsv[1])
 		return -EINVAL;
 
+	switch (extoff->clockid) {
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_MONOTONIC_RAW:
+		break;
+	case CLOCK_AUX ... CLOCK_AUX_LAST:
+		if (IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS))
+			break;
+		fallthrough;
+	default:
+		return -EINVAL;
+	}
+
 	sts.clockid = extoff->clockid;
 	for (unsigned int i = 0; i < extoff->n_samples; i++) {
 		struct timespec64 ts;
@@ -340,6 +349,11 @@ static long ptp_sys_offset_extended(stru
 		err = ptp->info->gettimex64(ptp->info, &ts, &sts);
 		if (err)
 			return err;
+
+		/* Filter out disabled or unavailable clocks */
+		if (sts.pre_ts.tv_sec < 0 || sts.post_ts.tv_sec < 0)
+			return -EINVAL;
+
 		extoff->ts[i][0].sec = sts.pre_ts.tv_sec;
 		extoff->ts[i][0].nsec = sts.pre_ts.tv_nsec;
 		extoff->ts[i][1].sec = ts.tv_sec;