I thought that I'd respond to some of your comments and questions
At 4:35 PM +0100 2/3/05, P.V. Machielse wrote:
I want to do the following: remap some keys on a _specific_
usb-keyboard. For instance: when I press the right option key, I
want it to be reported as 'enter'.
When I first started reading your question, I thought that
implementing a keyboard layout would be a better alternative than
implementing a replacement kernel extension. However, in the above
statement, one of the things which you desire is to modify the
behavior when a "modifier" key is pressed so that a different
keystroke is passed to the system. For this kind of change, a kernel
extension is required.
In my mind this calls for an iokit driver kernel extension. (please
correct me _now_ when there is a more elegant / user space way to
achieve the same thing).
because of the change to the modifier key behavior, a kext is required.
On the face of it, the task doesn't look too daunting. It should be
a simple matter of adapting the already available open source Apple
keyboard driver. Looking around on the Apple dev web site didn't
turn up (m)any clues about how usb keyboard input is handled, but
downloading the USBFamily.kext code made things a little clearer.
the IOUSBHIDDriver.cpp code does show that the process point for the
incoming report is with the
handleReport(_buffer) call line 1081.
At this point, the call takes you to the
IOHIDDevice::handleReport call in the IOHIDDevice.cpp file which is a
part of the IOHIDFamily source. The actual processing of the
keystroke is in the
IOHIDKeyboard::handleReport() call which is in the IOHIDKeyboard.cpp code.
Here you can see how the report is processed.
This should help get you started. What you should be able to do is
implement a vendor specific driver for your keyboard modeled after
the standard HID class driver. When the incoming report is received,
you have a chance to inspect the bytes and twiddle them to make it
appear that a keys were pressed or released.
For Tiger, a simpler mechanism will be introduced, but I don't have
the details for this.
rich
From the code, and from using kextstat, it seems that generic usb
keyboards are handled by the IOUSBHIDDriver kext, which is a 'plug
in' to IOUSBFamily.kext.
So now my initial questions are:
- Is writing a kext driver the right way to go?
- If so, is there any example code for keyboard drivers
- When I complete my kext, should it be installed in the plug
in folder of USBFamily
or can it remain at the top level of /System/Library/Extensions
I'm trying to figure out the flow of information from the hardware
through the system, but I'm having some trouble digging up the
correct documents. Any help is appreciated.
--
Sincerely,
Rich Kubota
email@hidden
(408) 974-6212
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