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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/