Re: [libgpiod] cxx bindings: time_point vs duration

[Helmut Grohne <helmut.grohne@xxxxxxxxxx>]

On Thu, Oct 15, 2020 at 01:43:32PM +0200, Bartosz Golaszewski wrote:
> Well, it's a long story. It used to be what the kernel calls REALTIME
> clock, then it was changed to MONOTONIC and now there's a suggestion
> to make it configurable in v2. More on that here[1].

Ouch. I was wodering already as the timestamps looked like REALTIME
here, but I'm simply using an older kernel. In that case the type of
your timestamps should depend on the Linux kernel version, which is
impossible to do. All you can do now is lie for older kernels.

> One question is: even if on linux the steady_clock is backed by
> CLOCK_MONOTONIC, is this a guarantee or just implementation? And can
> we rely on this if it's not defined?

Like the nanosecond resolution of steady_clock this is certainly not
guarantueed. However, it is rooted so deeply that it is very unlikely to
change. In theory, there could be a chance of changing it to
CLOCK_BOOTTIME. I don't think anyon is going to try.

At this point I recommend going with steady_clock.

Helmut