ptp: Add PHC timestamp quality attributes

This series adds quality attributes to PTP Hardware Clock (PHC)
timestamps, allowing userspace to obtain error bound, clock status,
timescale, and raw counter values alongside timestamps in a single
call.

Motivation
----------
The existing PTP APIs return timestamps without any indication of
their quality. Applications that need clock accuracy and
synchronization status commonly rely on external tools such as
ptp4l, which implement synchronization logic and can export their
measurement of clock accuracy. For managed PHC devices — such as
the ENA network adapter, whose clock is synchronized by the device
without userspace involvement — these tools are not available, and
the existing APIs lack a way to report quality metrics to consumers
of time.

This was previously proposed as an RFC [1] with a single ioctl.
Based on community feedback, the design was reworked to cover both
the extended (multi-sample) and precise (cross-timestamp) paths,
with a shared attributes structure.

Design
------
This series introduces two new ioctls that extend the existing
extended and precise timestamp paths with per-timestamp quality
attributes: error bound (nanoseconds), clock synchronization
status, timescale, and raw hardware counter values.

A capability flag is added to ptp_clock_caps so userspace can
discover attributes support.

Patches 2-3 add testptp support for the new ioctls.

Patch 4 implements the attributes for ptp_vmclock, reporting
error bound, clock status, timescale, and raw counter values.

Patches 5-8 implement the attributes for the ENA driver,
reporting error bound from the device's PHC layer.

[1] https://lore.kernel.org/netdev/20250724115657.150-1-darin...

Arthur Kiyanovski (8):
  ptp: Add ioctls for PHC timestamps with quality attributes
  selftests/ptp: Extract print_system_timestamp helper in testptp
  selftests/ptp: Add testptp support for attributes ioctls
  ptp: ptp_vmclock: Implement attributes ioctls
  net: ena: PHC: Check return code before setting timestamp output
  net: ena: Update PHC admin interface for error bound support
  net: ena: Add error bound to PHC communication layer
  net: ena: Implement gettimexattrs64 callback for PTP attributes

 .../device_drivers/ethernet/amazon/ena.rst    |   2 +
 .../net/ethernet/amazon/ena/ena_admin_defs.h  |  17 +-
 drivers/net/ethernet/amazon/ena/ena_com.c     |  47 ++--
 drivers/net/ethernet/amazon/ena/ena_com.h     |   5 +-
 drivers/net/ethernet/amazon/ena/ena_debugfs.c |   3 +
 drivers/net/ethernet/amazon/ena/ena_phc.c     |  67 +++++-
 drivers/ptp/ptp_chardev.c                     | 137 ++++++++++-
 drivers/ptp/ptp_clock.c                       |   4 +-
 drivers/ptp/ptp_vmclock.c                     | 195 +++++++++++++--
 include/linux/ptp_clock_kernel.h              |  30 +++
 include/uapi/linux/ptp_clock.h                | 225 +++++++++++++++++-
 tools/testing/selftests/ptp/testptp.c         | 175 ++++++++++----
 12 files changed, 799 insertions(+), 108 deletions(-)

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2.47.3