On 2 July 2024 19:12:00 BST, Peter Hilber [off-list ref] wrote:

On 02.07.24 18:39, David Woodhouse wrote:

quoted

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

quoted

 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.