Hmm, ok. Is there a specific distro you've in mind there? I got 2.6.31 out of the upstream git tree, but it's possible the COARSE clock was backported by some distros... not sure. I could try and check.

The truly correct thing to do is to check for it at runtime I suppose, and fall back to MONOTONIC_RAW. Problem is, go back far enough and all you have is MONOTONIC, which is skewed by ntp updates...