Re: [PATCH v3 3/4] Add support for driver cross-timestamp to PTP_SYS_OFFSET ioctl
From: Thomas Gleixner <hidden>
Date: 2015-08-22 20:34:28
Also in:
intel-wired-lan, lkml
On Fri, 21 Aug 2015, Christopher S. Hall wrote:
From: Christopher Hall <redacted>
This patch allows system and device time ("cross-timestamp") to be
performed by the driver. Currently, the cross-timestamping is performed
in the PTP_SYS_OFFSET ioctl. The PTP clock driver reads gettimeofday()
and the gettime64() callback provided by the driver. The cross-timestamp
is best effort where the latency between the capture of system time
(getnstimeofday()) and the device time (driver callback) may be
significant.
This patch adds an additional callback getsynctime64(). Which will be
called when the driver is able to perform a more accurate, implementation
specific cross-timestamping. For example, future network devices that
implement PCIE PTM will be able to precisely correlate the device clock
with the system clock with virtually zero latency between captures.
This added callback can be used by the driver to expose this functionality.
The callback, getsynctime64(), will only be called when defined and
n_samples == 1 because the driver returns only 1 cross-timestamp where
multiple samples cannot be chained together.
This patch also adds to the capabilities ioctl (PTP_CLOCK_GETCAPS),
allowing applications to query whether or not drivers implement the
getsynctime callback, providing more precise cross timestamping.That looks close to a proper changelog. A few nitpicks though. Please avoid 'This patch does ...' phrases. We already know that this is a patch.
Commit Details:
Please get rid of this. It's useless noise.
Added additional callback to ptp_clock_info: * getsynctime64()
quoted hunk ↗ jump to hunk
@@ -196,19 +197,31 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg) break; } pct = &sysoff->ts[0]; - for (i = 0; i < sysoff->n_samples; i++) { - getnstimeofday64(&ts); + if (ptp->info->getsynctime64 && sysoff->n_samples == 1 &&
The number of samples should be irrelevant for this sampling method.
+ ptp->info->getsynctime64(ptp->info, &ts, &systs) == 0) {Why is this function taking struct timespec64 pointers? Just so every driver which implements the callback needs to convert from u64 to struct timespec64? That's simply wrong. Use u64 for both and do the conversion in the ioctl. Thanks, tglx