On Thu, 2025-07-24 at 14:56 +0300, David Arinzon wrote:

The proposed PTP_SYS_OFFSET_EXTENDED_TRUSTED ioctl fulfills both
objectives by extending each PHC timestamp with two quality
indicators:

- error_bound: a device-calculated value (in nanoseconds)
  reflecting the maximum possible deviation of the timestamp from
  the true time, based on internal clock state.

- clock_status: a qualitative state of the clock, with defined
  values including:
  1. Unknown: the clock's synchronization status cannot be
     reliably determined.
  2. Initializing: the clock is acquiring synchronization.
  3. Synchronized: The clock is actively being synchronized and
     maintained accurately by the device.
  4. FreeRunning: the clock is drifting and not being
     synchronized and updated by the device.
  5. Unreliable: the clock is known to be unreliable, the
     error_bound value cannot be trusted.

Should this also include a 'type' field matching vmclock & virtio-rtc?
Especially if it's a smeared type, that is a (contra-)indication of the
quality of the clock.

Julien, I assume you're happy that this is *maxerror* and we completely
ignore esterror which should never exist anyway?