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[hr_rabe]

I am currently trying to map gamepad controls in a Cocoa application, using Apple's HIDManager api.

However, I ran into a problem, and can't find an easy solution to it.

From examination, it seems to me, that the only way I can identify distinct control updates (button presses and stick movement) is via an integer identifier, I get back from the HIDElementGetCookie(element) function. But this identifier is completely vendor specific as far as I know.

For example, on my simple logitech Gamepad, the Cookie 18 describes the X-Axis of the left analog stick, whereas on the PS3 controller the same Cookie value describes the upper-right shoulder button.

Is there any technique or reliable other method, how I can identify specific elements of a controller?

To add some code to my question, here is the HID callback function, that handles the control update:

void gamepadAction(void* inContext, IOReturn inResult,
				   void* inSender, IOHIDValueRef value) {
  
	IOHIDElementRef element = IOHIDValueGetElement(value);
	Boolean isElement = CFGetTypeID(element) == IOHIDElementGetTypeID();
	if (!isElement)
		return;
	IOHIDElementCookie cookie = IOHIDElementGetCookie(element);
	IOHIDElementType type = IOHIDElementGetType(element);
	if (18 != cookie && 19 != cookie && 21 != cookie){
		NSLog(@"Gamepad talked rubbish at %d of type %d", cookie, type);
		return;
	}
  
	IOHIDElementCollectionType ctype = IOHIDElementGetCollectionType(element);
	CFStringRef name = IOHIDElementGetName(element);
  
	long elementValue = IOHIDValueGetIntegerValue(value);
	NSLog(@"Gamepad talked: %d / %d - %@ [%i] = %ld", type, ctype, name,
		  cookie, elementValue);
  
	if (18 == cookie || 19 == cookie || 21 == cookie){
		MyGameController* obj = (__bridge MyGameController*) inContext;
		float axisScale = 128;
	  
		float axisvalue = ((float)(elementValue-axisScale)/axisScale);
		if (elementValue <= axisScale +1 &&
			elementValue >= axisScale -1)
			axisvalue = 0.0;
		if (18 == cookie)
			[obj setLatitude:axisvalue];
		else if (21 == cookie)
			[obj setCenterDistance:axisvalue];
		else if (19 == cookie)
			[obj setLongitude:axisvalue];
	}  
}

[hr_rabe]

I solved the problem myself now.

For anyone interested:

The HID-Cookies are a dead end, because they are immensly provider specific and can't be relied upon. If one would want to use a Cookie-Based System, one would need to provide Custom mappings for any Gamepad that should be able to control the game.

A better solution is to read the UsagePage and UsageKey from the origin element of the value and us the combination of those, to identify the sender element.

Because those are standardized and can be found at http://www.usb.org/developers/devclass_docs/Hut1_11.pdf. So the UsagePage/Usage combination 1/48 will always refer to the X-Achsis of the gamepads Left analog stick

Here's the fixed code, for anyone who's interested:

void gamepadAction(void* inContext, IOReturn inResult,
				   void* inSender, IOHIDValueRef value) {
   
    IOHIDElementRef element = IOHIDValueGetElement(value);
    Boolean isElement = CFGetTypeID(element) == IOHIDElementGetTypeID();
    if (!isElement)
	    return;
    IOHIDElementCookie cookie = IOHIDElementGetCookie(element);
    IOHIDElementType type = IOHIDElementGetType(element);
    CFStringRef name = IOHIDElementGetName(element);
    int usagePage = IOHIDElementGetUsagePage(element);
    int usage = IOHIDElementGetUsage(element);
    if (1 != usagePage)
	    return;
   
    long elementValue = IOHIDValueGetIntegerValue(value);
    NSLog(@"Gamepad talked: %d / %d - %@ [%i] = %ld", type, usage, name,
		  cookie, elementValue);
   
    if (48 == usage || 49 == usage || 53 == usage){
	    MyGameController* obj = (__bridge MyGameController*) inContext;
	    float axisScale = 128;
	   
	    float axisvalue = ((float)(elementValue-axisScale)/axisScale);
	    if (elementValue <= axisScale +1 &&
		    elementValue >= axisScale -1)
		    axisvalue = 0.0;
	    if (48 == usage)
		    [obj setLatitude:axisvalue];
	    else if (53 == usage)
		    [obj setCenterDistance:axisvalue];
	    else if (49 == usage)
		    [obj setLongitude:axisvalue];
    }
   
}