[PATCH net-next v5 0/6] ptp: Support for multiple filtered timestamp event queue readers

[Xabier Marquiegui <reibax@gmail.com>]

On systems with multiple timestamp event channels, there can be scenarios
where multiple userspace readers want to access the timestamping data for
various purposes.

One such example is wanting to use a pps out for time synchronization, and
wanting to timestamp external events with the synchronized time base 
simultaneously.

Timestmp event consumers on the other hand, are often interested in a
subset of the available timestamp channels. linuxptp ts2phc, for example,
is not happy if more than one timestamping channel is active on the device
it is reading from.

This patch-set introduces linked lists to support multiple timestamp event
queue consumers, and timestamp event channel filters through IOCTLs, as
well as a debugfs interface to do some simple verifications.

Xabier Marquiegui (6):
  posix-clock: introduce posix_clock_context concept
  ptp: Replace timestamp event queue with linked list
  ptp: support multiple timestamp event readers
  ptp: support event queue reader channel masks
  ptp: add debugfs interface to see applied channel masks
  ptp: add testptp mask test

 drivers/ptp/ptp_chardev.c                   | 129 ++++++++++++++++----
 drivers/ptp/ptp_clock.c                     |  45 ++++++-
 drivers/ptp/ptp_private.h                   |  28 +++--
 drivers/ptp/ptp_sysfs.c                     |  13 +-
 include/linux/posix-clock.h                 |  22 ++--
 include/uapi/linux/ptp_clock.h              |   2 +
 kernel/time/posix-clock.c                   |  36 ++++--
 tools/testing/selftests/ptp/ptpchmaskfmt.sh |  14 +++
 tools/testing/selftests/ptp/testptp.c       |  19 ++-
 9 files changed, 248 insertions(+), 60 deletions(-)
 create mode 100644 tools/testing/selftests/ptp/ptpchmaskfmt.sh

Signed-off-by: Xabier Marquiegui <reibax@gmail.com>
Suggested-by: Richard Cochran <richardcochran@gmail.com>
Suggested-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
---
v5:
  - fix spelling on commit message
  - fix memory leak on ptp_open
v4: https://lore.kernel.org/netdev/cover.1696511486.git.reibax@gmail.com/
  - split modifications in different patches for improved organization
  - rename posix_clock_user to posix_clock_context
  - remove unnecessary flush_users clock operation
  - remove unnecessary tests
  - simpler queue clean procedure
  - fix/clean comment lines
  - simplified release procedures
  - filter modifications exclusive to currently open instance for
    simplicity and security
  - expand mask to 2048 channels
  - make more secure and simple: mask is only applied to the testptp
    instance. Use debugfs to verify effects.
v3: https://lore.kernel.org/netdev/20230928133544.3642650-1-reibax@gmail.com/
  - add this patchset overview file
  - fix use of safe and non safe linked lists for loops
  - introduce new posix_clock private_data and ida object ids for better
    dicrimination of timestamp consumers
  - safer resource release procedures
  - filter application by object id, aided by process id
  - friendlier testptp implementation of event queue channel filters
v2: https://lore.kernel.org/netdev/20230912220217.2008895-1-reibax@gmail.com/
  - fix ptp_poll() return value
  - Style changes to comform to checkpatch strict suggestions
  - more coherent ptp_read error exit routines
  - fix testptp compilation error: unknown type name 'pid_t'
  - rename mask variable for easier code traceability
  - more detailed commit message with two examples
v1: https://lore.kernel.org/netdev/20230906104754.1324412-2-reibax@gmail.com/
---