The cpuidle subsystem

Is there anywhere a list of supporting processors? I was hoping that a site like lesswatts.org might have that sort of thing, but I couldn't find that information anywhere short of downloading the datasheets for every individual CPU, and of course there are a near-infinite selection of CPUs on offer nowadays.

However, if even brand new all-in-one Atom systems don't support this - given that they're targetted specifically at low-power uses - it doesn't seem to be a stretch to conclude that this is something that manufacturers basically don't care about.