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I’ve been buying broken Macbook’s in SA when I’ve been home, for repair in China.

My latest purchase is a pre unibody Mac Book Pro that had been dropped – the top case was dented,and the screen shattered.
The LCD was fairly painless to replace – I’ve done quite a few already on various models, and I have a bazillion suppliers for raw panels.

The top case was a little more problematic – I ordered 2 consecutive replacements off of Taobao, but unfortunately the delivery company (ShenTong) destroyed both in shipping. Took about a month to sort that out and find a yet another replacement with explicit instructions please not to send via ShenTong (aka destroyer of parts).

The third case arrived in pristine condition, and I installed the keyboard from the previous case, only to find that the function keys didn’t work, and the caps lock didn’t work.

It wasn’t a hardware issue with the keyboard, as it worked fine in another laptop. I even ordered another one just to make sure.

A bit of googling revealed that the keyboard kext gets the layout from the USB hardware ID present in the top case.
As my top case didn’t quite match up hardware id wise, I was seeing that as an issue.

Fixing this is a bit tricky, but doable.

First up was to find out what the hardware id is for the USB case.
In my case this was as below (snarfed from System Information / USB)

Apple Internal Keyboard / Trackpad:

  Product ID:	0x0231
  Vendor ID:	0x05ac  (Apple Inc.)
  Version:	0,70
  Speed:	Up to 12 Mb/sec
  Manufacturer:	Apple, Inc.
  Location ID:	0x5d200000 / 3
  Current Available (mA):	500
  Current Required (mA):	40

Product ID is the useful bit – 0x0231 = 561 in decimal.
So, we need to lookup 561 in the kext (driver) for the keyboard.

In Lion / Snow Leopard, this is in the AppleUSBTopCase.kext over in System / Library / Extensions.

If you open up that kext, it has the plist for the keyboard layouts over here –

AppleUSBTopCase.kext » Contents » PlugIns » AppleUSBTCKeyEventDriver.kext » Contents » Info.plist

Open up the Info.plist, and look for the Product ID that matches your Product ID – in my case 560.

The key FnFunctionUsageMap contains the mapping for the keyboard. In my case I had to change it to this:


Each value is a pair – first the key number, then the value to set it to.
0x0007003a = F1
0x0007003b = F2

My above settings are for
F1 = brightness down
F2 = brightness up
F3 = mute
F4 = volume down
F5 = volume up
F6 = num lock
F7 = Expose
F8 = Keyboard Light off
F9 = Keyboard Light down
F10 = Keyboard Light Up
F11 = n/a
F12 = n/a

I got these values from here –

// usage IDs from the hid
#define FF_BRIGHTNESS_DOWN_ID_LAPTOP @”0x00ff0005″ // for laptops
#define FF_BRIGHTNESS_UP_ID_LAPTOP @”0x00ff0004″ // for laptops
#define FF_BRIGHTNESS_DOWN_ID_EXTERNAL @”0xff010021″ // for external keyboards
#define FF_BRIGHTNESS_UP_ID_EXTERNAL @”0xff010020″ // for external keyboards
#define FF_EXPOSE_ID @”0xff010010″
#define FF_DASHBOARD_ID @”0xff010002″
#define FF_ILLUMINATION_TOGGLE_ID @”0x00ff0007″
#define FF_ILLUMINATION_DOWN_ID @”0x00ff0009″
#define FF_ILLUMINATION_UP_ID @”0x00ff0008″
#define FF_VIDEO_MIRROR_ID @”0x00ff0006″
#define FF_REWIND_ID @”0x000C00B4″
#define FF_PLAYPAUSE_ID @”0x000C00CD”
#define FF_FASTFORWARD_ID @”0x000C00B3″
#define FF_MUTE_ID @”0x000C00E2″
#define FF_VOLUME_DOWN_ID @”0x000C00EA”
#define FF_VOLUME_UP_ID @”0x000C00E9″

Once I’d done that, I also needed to rebuild (or in my case build), the Kext cache so that the OS would use it on next reboot.
Heres how to do that in Lion

sudo kextcache -v 1 -a i386 -a x86_64 -m /System/Library/Caches/ /System/Library/Extensions

…oh, and lastly, reboot of course!

Post reboot my function keys were working normally.
The caps lock key is still non-functional, but I’m ok with that, as its means a bit more work for little effort.

I may look into setting up a special plist to override the usb_id its getting from the hardware via the method here –

..but again, time vs effort…

Still, my Macbook is working now more or less, so its good enough for me 🙂

Of course, subsequently to doing this the hard way, I found a program to do it all for me!

Suggest unless you are a masochist, use that!