ptp: add an ioctl to compare PHC time with system time

This patch adds an ioctl for PTP Hardware Clock (PHC) devices that allows
user space to measure the time offset between the PHC and the system
clock. Rather than hard coding any kind of estimation algorithm into the
kernel, this patch takes the more flexible approach of just delivering
an array of raw clock readings. In that way, the user space clock servo
may be adapted to new and different hardware clocks.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 32 insertions, 0 deletions

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index e7f301da2..4f8ae80 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -33,9 +33,13 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 {
 	struct ptp_clock_caps caps;
 	struct ptp_clock_request req;
+	struct ptp_sys_offset sysoff;
 	struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
 	struct ptp_clock_info *ops = ptp->info;
+	struct ptp_clock_time *pct;
+	struct timespec ts;
 	int enable, err = 0;
+	unsigned int i;
 
 	switch (cmd) {
 
@@ -88,6 +92,34 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 		err = ops->enable(ops, &req, enable);
 		break;
 
+	case PTP_SYS_OFFSET:
+		if (copy_from_user(&sysoff, (void __user *)arg,
+				   sizeof(sysoff))) {
+			err = -EFAULT;
+			break;
+		}
+		if (sysoff.n_samples > PTP_MAX_SAMPLES) {
+			err = -EINVAL;
+			break;
+		}
+		pct = &sysoff.ts[0];
+		for (i = 0; i < sysoff.n_samples; i++) {
+			getnstimeofday(&ts);
+			pct->sec = ts.tv_sec;
+			pct->nsec = ts.tv_nsec;
+			pct++;
+			ptp->info->gettime(ptp->info, &ts);
+			pct->sec = ts.tv_sec;
+			pct->nsec = ts.tv_nsec;
+			pct++;
+		}
+		getnstimeofday(&ts);
+		pct->sec = ts.tv_sec;
+		pct->nsec = ts.tv_nsec;
+		if (copy_to_user((void __user *)arg, &sysoff, sizeof(sysoff)))
+			err = -EFAULT;
+		break;
+
 	default:
 		err = -ENOTTY;
 		break;