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.
Christopher Hall (1):
Added additional callback to ptp_clock_info:
drivers/ptp/ptp_chardev.c | 29 +++++++++++++++++++++--------
include/linux/ptp_clock_kernel.h | 8 ++++++++
include/uapi/linux/ptp_clock.h | 4 +++-
3 files changed, 32 insertions(+), 9 deletions(-)
--
1.9.1
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