[RFC v2 0/2] ptp: Move non-NIC PHC drivers from netdev to clock/timekeeping maintainership

[Wen Gu <guwen@linux.alibaba.com>]

Hi all,

This RFC v2 is a follow-up to [1].


# Background

The PTP Hardware Clock (PHC) interface (/dev/ptpX and the standard PTP_*
ioctls) was originally introduced for IEEE 1588 / network oriented clock
drivers. Over time, it has also become a common userspace API for many non-NIC
high-precision clock implementations (virtualization/platform/architecture
provided clocks) [2-6], and more are expected to appear [7-8].

During the review of these incoming non IEEE 1588 based PHC drivers, concerns
were raised that such "non-NIC" clocks may not be a good fit for the netdev
maintainership model [9], where PTP/PHC drivers are currently maintained. This
leaves an unclear upstream home and maintainership model for this class of
drivers.


# Proposal

This RFC proposes moving PHC drivers that expose a high-precision clock to
userspace via the existing PTP interface (/dev/ptpX + standard PTP_* ioctls),
but are not tied to the traditional NIC/IEEE 1588 packet timestamping
pipeline, out of the netdev maintainership scope and into a clock/timekeeping
maintainership scope.

As discussed in [1], this series makes the separation explicit by splitting
drivers/ptp/ into the following groups, to prepare for clearer ownership and
future maintenance:

  - drivers/ptp/          : PTP core infrastructure and userspace ABI
                            (ptp_clock.c, ptp_chardev.c, ptp_sysfs.c,
                             ptp_vclock.c, etc.) remain here.

  - drivers/ptp/ieee1588/ : network / IEEE 1588 oriented PTP drivers.

  - drivers/ptp/emulated/ : non IEEE 1588 PTP drivers. they are typically
                            platform/architecture/virtualization/speical
                            hardware provided high precision time sources.

Patch 1 performs the refactor: move drivers and split Kconfig/Makefiles
accordingly, without intended functional changes.

Patch 2 updates MAINTAINERS to match the new layout and adds a dedicated entry
for drivers/ptp/emulated/, moving review and ownership routing for this class
of drivers away from the netdev maintainership.

No userspace ABI changes are intended, this is a refactor and maintenance
metadata update only.


# Request for comments

1. Following the clocksource/timekeeping and POSIX timer areas, this RFC routes
changes for drivers/ptp/emulated/ to linux-kernel@vger.kernel.org (rather than
netdev). However, the preferred integration path is still unclear (e.g. which
tree should take such changes, and who should collect/pull them for merging). We
would really appreciate guidance from the time/clock maintainers, especially any
input from Thomas Gleixner, on the preferred tree/workflow for these changes.

2. This RFC currently lists us as the maintainers for drivers/ptp/emulated/ as a
fallback contact point. Ideally, we would prefer this area to be maintained by
clock/time experts in the long run. Suggestions on more suitable maintainers are
very welcome.


Thanks for any input.

Regards.

[1] https://lore.kernel.org/all/0afe19db-9c7f-4228-9fc2-f7b34c4bc227@linux.alibaba.com/
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a0e136d436ded817c0aade72efdefa56a00b4e5e
[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7d10001e20e46ad6ad95622164686bc2cbfc9802
[4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2d7de7a3010d713fb89b7ba99e6fdc14475ad106
[5] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3716a49a81ba19dda7202633a68b28564ba95eb5
[6] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9a17125a18f9ae1e1233a8e2d919059445b9d6fd
[7] https://lore.kernel.org/netdev/20251030121314.56729-1-guwen@linux.alibaba.com/
[8] https://lore.kernel.org/mhi/20250818-tsc_time_sync-v1-0-2747710693ba@oss.qualcomm.com/
[9] https://lore.kernel.org/netdev/20251127083610.6b66a728@kernel.org/

Wen Gu (2):
  ptp: split clock drivers into two subdirectories
  MAINTAINERS: update PTP maintainer entries after directory split

 MAINTAINERS                                  |  39 ++-
 drivers/ptp/Kconfig                          | 255 ++-----------------
 drivers/ptp/Makefile                         |  27 +-
 drivers/ptp/emulated/Kconfig                 |  81 ++++++
 drivers/ptp/emulated/Makefile                |  12 +
 drivers/ptp/{ => emulated}/ptp_kvm_arm.c     |   0
 drivers/ptp/{ => emulated}/ptp_kvm_common.c  |   0
 drivers/ptp/{ => emulated}/ptp_kvm_x86.c     |   0
 drivers/ptp/{ => emulated}/ptp_ocp.c         |   0
 drivers/ptp/{ => emulated}/ptp_s390.c        |   0
 drivers/ptp/{ => emulated}/ptp_vmclock.c     |   0
 drivers/ptp/{ => emulated}/ptp_vmw.c         |   0
 drivers/ptp/ieee1588/Kconfig                 | 159 ++++++++++++
 drivers/ptp/ieee1588/Makefile                |  15 ++
 drivers/ptp/{ => ieee1588}/ptp_clockmatrix.c |   0
 drivers/ptp/{ => ieee1588}/ptp_clockmatrix.h |   0
 drivers/ptp/{ => ieee1588}/ptp_dfl_tod.c     |   0
 drivers/ptp/{ => ieee1588}/ptp_dte.c         |   0
 drivers/ptp/{ => ieee1588}/ptp_fc3.c         |   0
 drivers/ptp/{ => ieee1588}/ptp_fc3.h         |   0
 drivers/ptp/{ => ieee1588}/ptp_idt82p33.c    |   0
 drivers/ptp/{ => ieee1588}/ptp_idt82p33.h    |   0
 drivers/ptp/{ => ieee1588}/ptp_ines.c        |   0
 drivers/ptp/{ => ieee1588}/ptp_mock.c        |   0
 drivers/ptp/{ => ieee1588}/ptp_netc.c        |   0
 drivers/ptp/{ => ieee1588}/ptp_pch.c         |   0
 drivers/ptp/{ => ieee1588}/ptp_qoriq.c       |   0
 27 files changed, 322 insertions(+), 266 deletions(-)
 create mode 100644 drivers/ptp/emulated/Kconfig
 create mode 100644 drivers/ptp/emulated/Makefile
 rename drivers/ptp/{ => emulated}/ptp_kvm_arm.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_kvm_common.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_kvm_x86.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_ocp.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_s390.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_vmclock.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_vmw.c (100%)
 create mode 100644 drivers/ptp/ieee1588/Kconfig
 create mode 100644 drivers/ptp/ieee1588/Makefile
 rename drivers/ptp/{ => ieee1588}/ptp_clockmatrix.c (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_clockmatrix.h (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_dfl_tod.c (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_dte.c (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_fc3.c (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_fc3.h (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_idt82p33.c (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_idt82p33.h (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_ines.c (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_mock.c (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_netc.c (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_pch.c (100%)
 rename drivers/ptp/{ => ieee1588}/ptp_qoriq.c (100%)

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2.43.5