Re: [PATCH net-next v5 1/2] ptp: introduce Alibaba CIPU PHC driver

[Wen Gu]

On 2025/11/6 08:24, Jakub Kicinski wrote:
> On Wed, 5 Nov 2025 18:22:19 +0800 Wen Gu wrote:
> > On 2025/11/1 07:58, Jakub Kicinski wrote:
> > > On Thu, 30 Oct 2025 20:13:13 +0800 Wen Gu wrote:
> > > > This adds a driver for Alibaba CIPU PTP clock. The CIPU, an underlying
> > > > infrastructure of Alibaba Cloud, synchronizes time with atomic clocks
> > > > via the network and provides microsecond or sub-microsecond precision
> > > > timestamps for VMs and bare metals on cloud.
> > > >
> > > > User space processes, such as chrony, running in VMs or on bare metals
> > > > can get the high precision time through the PTP device exposed by this
> > > > driver.
> > >
> > > As mentioned on previous revisions this is a pure clock device which has
> > > nothing to do with networking and PTP.
> >
> > I don't quite agree that this has nothing to do with PTP.
> >
> > What is the difference between this CIPU PTP driver and other PTP drivers
> > under drivers/ptp? such as ptp_s390, ptp_vmw, ptp_pch, and others. Most of
> > these PTP drivers do not directly involve IEEE 1588 or networking as well.

Sorry for the late reply due to a vacation.

> We can't delete existing drivers. It used to be far less annoying
> until every cloud vendor under the sun decided to hack up their own
> implementation of something as simple as the clock.

So what kind of drivers do you think are qualified to be placed in the
drivers/ptp? I checked some docs, e.g.[1], and codes in drivers/ptp,
but I am not sure what the deciding factor is, assuming that exposing
a PTP character device is not sufficient.

[1] https://docs.kernel.org/driver-api/ptp.html

Regards.

> > > There should be a separate class
> > > for "hypervisor clocks", if not a common driver.
> >
> > 'hypervisor clock' is not very accurate. CIPU PTP can be used in VM and
> > bare metal scenarios, and bare metals do not need hypervisors.
>
> I know.