Fixes for loss of keyboard, mouse recognition

Fixes for loss of keyboard, mouse recognition

We previously reported on an issue where various Macs (usually portables) suddenly lose their ability to use both the built-in trackpad/keyboard (if applicable) and external (USB) keyboards and mice in one of the following ways:

  • No input from built-in trackpad and keyboard is recognized. External USB keyboards and mice can be connected to regain control.
  • Input from both built-in and external input devices (keyboards, mice, trackpads) is not recognized.
  • Keyboard/trackpad/mouse input is sent to the wrong window

This problem is especially likely to occur after a Mac wakes from sleep or safe sleep.

Some additional fixes for this issue have now been identified:

Unplug then re-plug, switch ports One of the simplest solutions for USB-based input devices that suddenly stop functioning is to unplug then reconnect them. Doing so can eliminate arbitration problems and other issues preventing normal use. Switching the USB port to which a given device is connected can have a similar effect.

MacFixIt reader David Wagner offers a case example:

"I just had this happen with a PowerMac G4, which had the mouse plugged in to the keyboard, and the keyboard plugged into the Apple 17" LCD display. Unplugging the USB cable from the display, and plugging it into my IOGEAR 4-port USB card, resulted in restored function for mouse and keyboard."

Restart kernel extensions Some users have reported that unloading then re-loading appropriate kernel extensions can resolve this issue -- especially with regard to trackpads that stop functioning after sleep. This can be accomplished by opening the Terminal (located in Applications/Utilities) and entering the following two commands (in order) and pressing return after each. You will be prompted for your administrator password.

  1. sudo kextunload /System/Library/Extensions/AppleUSBTopCase.kext/Contents/PlugIns/AppleUSBTrackpad.kext
  2. sudo kextload /System/Library/Extensions/AppleUSBTopCase.kext/Contents/PlugIns/AppleUSBTrackpad.kext

One reader who had success with this fix writes:

"I've been seeing this issue (loss of keyboard/trackpad) ever since the latest firmware update on my original black macbook. When the trackpad completely stops working, i unload and reload the relevant kext.

"Sometimes, i just lose the ability to click. My workaround has been to use mousekeys to check and uncheck 'clicking' under mousepad gestures in the Keyboard and Mouse preferences pane.

"Sometimes, i only lose the ability to use two fingers to right-click. If I unload and reload the kext, that option disappears completely from the prefpane as if i were on an older mac. The only solution i've found is to reboot."

Feedback? Late-breakers@macfixit.com.

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