Re: [RFC PATCH v2] ptp: Add vDSO-style vmclock support

Peter Hilber
2024-07-03T09:56:54Z

On 02.07.24 20:40, David Woodhouse wrote:
> On 2 July 2024 19:12:00 BST, Peter Hilber <peter.hilber@opensynergy.com> wrote:
>> On 02.07.24 18:39, David Woodhouse wrote:
>>> To clarify then, the main types are
>>>
>>> VIRTIO_RTC_CLOCK_UTC == 0
>>> VIRTIO_RTC_CLOCK_TAI == 1
>>> VIRTIO_RTC_CLOCK_MONOTONIC == 2
>>> VIRTIO_RTC_CLOCK_SMEARED_UTC == 3
>>>
>>> And the subtypes are *only* for the case of
>>> VIRTIO_RTC_CLOCK_SMEARED_UTC. They include
>>>
>>> VIRTIO_RTC_SUBTYPE_STRICT
>>> VIRTIO_RTC_SUBTYPE_UNDEFINED /* or whatever you want to call it */
>>> VIRTIO_RTC_SUBTYPE_SMEAR_NOON_LINEAR
>>> VIRTIO_RTC_SUBTYPE_UTC_SLS /* if it's worth doing this one */
>>>
>>> Is that what we just agreed on?
>>>
>>>
>>
>> This is a misunderstanding. My idea was that the main types are
>>
>>> VIRTIO_RTC_CLOCK_UTC == 0
>>> VIRTIO_RTC_CLOCK_TAI == 1
>>> VIRTIO_RTC_CLOCK_MONOTONIC == 2
>>> VIRTIO_RTC_CLOCK_SMEARED_UTC == 3
>>
>> VIRTIO_RTC_CLOCK_MAYBE_SMEARED_UTC == 4
>>
>> The subtypes would be (1st for clocks other than
>> VIRTIO_RTC_CLOCK_SMEARED_UTC, 2nd to last for
>> VIRTIO_RTC_CLOCK_SMEARED_UTC):
>>
>> #define VIRTIO_RTC_SUBTYPE_STRICT 0
>> #define VIRTIO_RTC_SUBTYPE_SMEAR_NOON_LINEAR 1
>> #define VIRTIO_RTC_SUBTYPE_SMEAR_UTC_SLS 2
>>
>
> Thanks. I really do think that from the guest point of view there's really no distinction between "maybe smeared" and "undefined smearing", and have a preference for using the latter form, which is the key difference there?
>
> Again though, not a hill for me to die on.

I have no issue with staying with "undefined smearing", so would you agree
to something like

VIRTIO_RTC_CLOCK_SMEAR_UNDEFINED_UTC == 4

(or another name if you prefer)?