mm-qcamera-daemon causing massive battery drain Recently, mm-qcamera-daemon has been causing massive battery drain on my Nexus 5, and making it become rather warm. At the same time, the camera appears to be locked, meaning opening the default camera app (or any camera app) causes the alert Camera is currently in use to appear.

Numerous forums around the web site apps such as Snapchat and a Yahoo video app as the issues, but I've never installed these apps before.

Restarting the phone does seem to fix the issue, but after awhile (more than 12h) later, the battery starts draining again.



UPDATE: Like the top answer says, this problem should have been fixed by the 4.4.4 Kitkat update that rolled out.
Solution: 

Wait for the next Android maintenance update:

Comment #475 on issue 60058


  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.
  
  More details:
  
  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.