4540s won't stay asleep

[RehabMan]

Short answer: Yosemite 10.10.2 update seems to have fixed this (as others have reported elsewhere), and my probook is now sleeping like a baby.

Longer answer in case anyone cares: It wasn't any plugged in USB device, as I verified that the problem existed multiple times when absolutely nothing was plugged in.

The problem seems as if it had three different parts:

1. The computer instisted on an RTC-driven DarkWake within a couple hours of going to sleep, every time.
2. Upon Darkwake, it would apparently think there was HID input, and come fully awake.
3. Sometimes it would cycle like this every couple of hours, but other times, after it had done this once it would never go to sleep again until I had actually used the system even though there were no pmset assertions listed.

I believe that the Yosemite update fixed problem number 1. nguyenmac had suggested an mDNSresponder fix via a command line option. But with Yosemite mDNSresponder was completely replaced with discoveryd which no longer had this option. So as a guess, I think they fixed discoveryd so that it no longer requests a DarkWake when there are no services that would actually be interested in using it. At any rate, there are no longer any DarkWakes in the log.

I have no idea if the other issues were also fixed by the update, but I don't think I'll ever even see them now that my probook is nolonger doing a darkwake after just a couple of hours.

Probably so... I believe the mDNSresponder/discoverd also affected real Macs as well. Many of the newer Macs have no outward indication of sleep vs. darkwake, so only those that looked at their system.log would notice. And of course, real Macs have no issue with darkwake.

If your laptop has a problem with darkwake, that issue is probably still there... and now that the unnecessary darkwake events are not happening, the problem will simply occur less often... only when a real darkwake event occurs.