Thanks, everyone, for reporting about this problem.
We believe we have fixes for the current high CPU reports on N5 due to mm-qcamera-daemon, and they will be included in the next maintenance update. At this point, we don't need more reports of the problem, with some exceptions I'll detail below.
We've had scattered reports of persistent high CPU usage of mm-qcamera-daemon since our last maintenance update, and based on those, found a number of bugs that were then fixed.
More recently, there's been a significant increase in the frequency of reported problems. These may be related to a recent update to Skype, which seems to access the camera regularly from its background service in some way that triggers this bug (note, we don't currently believe there's a bug in Skype itself). Investigating this, we've identified a few additional fixes that we hope resolve this issue for good. However, since the high CPU usage is an intermittent problem, we're continuing to test our fixes to verify the problems are gone.
Unfortunately, I can't provide an estimate for when the maintenance update will be ready, due to all the testing we need to do for this and other fixes. Until then, rebooting the phone is the only way to stop the high CPU usage/lack of camera function once it starts.
Uninstalling Skype may substantially reduce the likelihood of this bug appearing, but I realize Skype is a very important application for many people. Other camera-using applications may trigger this bug as well, but that's been relatively rare. Most applications also do not access the camera when not in the foreground, so they will only trigger issues when actively used.
I'd also like to note that instances of high CPU use of mm-qcamera-daemon on other devices besides the N5 need to be reported to their manufacturers - while those devices also use a Qualcomm chip for their camera processing (and thus have a mm-qcamera-daemon process), each has differences in their software and issues with them do not necessarily mean the N5 has the same problem, and vice versa.
If you are seeing high CPU use of mm-qcamera-daemon, and you have not used the camera at all, or installed an application like Skype that has a background service that accesses the camera (typically, applications that provide video chat may do this), we would like to know about it.
Otherwise, for Skype and other typical camera applications, we believe we have fixes identified, and you don't need to add more information to this bug - remember, any note added here will send updates to dozens of people.
Please open a new bug with a description, and if possible, system logs and/or an Android bugreport captured when you see high battery use.