LinuxClock::system_offset is wrong about UnixClock::system_offset timescale?

[teodly]

In statime-linux, system_offset expects UnixClock::system_offset (from clock-steering) to be REALTIME:

        // The clock crate's system offset gives the T1 and T3 timestamps on the
        // CLOCK_REALTIME timescale which is UTC, not TAI, so we need to correct
        // here.

            let tai_offset = UnixClock::CLOCK_REALTIME.get_tai().unwrap();
            t1.seconds += tai_offset as libc::time_t;
            t3.seconds += tai_offset as libc::time_t;

However, here, clock-steering uses TAI, both in fallback userspace timestamp sandwitching:

            let t1 = Self::CLOCK_TAI.now();
            let tp = self.now();
            let t2 = Self::CLOCK_TAI.now();

and it already converts PTP_SYS_OFFSET result which is REALTIME to TAI:

            let tai_offset = Self::CLOCK_TAI.get_tai()?;

            Ok((
                Timestamp {
                    seconds: (offset.ts[0].sec + tai_offset as i64) as _,
                    nanos: offset.ts[0].nsec as _,
                },
                Timestamp {
                    seconds: offset.ts[1].sec as _,
                    nanos: offset.ts[1].nsec as _,
                },
                Timestamp {
                    seconds: (offset.ts[2].sec + tai_offset as i64) as _,
                    nanos: offset.ts[2].nsec as _,
                },
            ))

So is it really wrong or am I missing something?

[teodly]

I think I know what's going on. The logic is incorrect but works correctly by accident (at least on my system which apparently supports PTP_SYS_OFFSET). I have written additional test:

    #[test]
    fn get_tai() {
        println!("tai from TAI: {}", UnixClock::CLOCK_TAI.get_tai().unwrap());
        println!("tai from REALTIME: {}", UnixClock::CLOCK_REALTIME.get_tai().unwrap());
    }

and got this:

tai from TAI: 0
tai from REALTIME: 37

So, get_tai() method works correctly only for REALTIME. It should be changed to associated function without self argument, because, according to docstring, it always returns difference between TAI and UTC.