I am trying to add instance variables to my DriverKit class. I declare them in the class definition in the .iig file but when i try to access them in the .cpp file i get an error "Use of undeclared identifier". Is there a limitation that prevents instance variables in the classes defined for DriverKit?
.iig file
class VirtualJoystick: public IOUserUSBHostHIDDevice
{
public:
virtual kern_return_t
Start(IOService * provider) override;
virtual kern_return_t
Stop(IOService * provider) override;
virtual bool init() override;
virtual void free() override;
virtual OSDictionary * newDeviceDescription(void) override;
virtual OSData * newReportDescriptor(void) override;
virtual kern_return_t getReport(
IOMemoryDescriptor *report,
IOHIDReportType reportType,
IOOptionBits options,
uint32_t completionTimeout,
OSAction *action
) override;
private:
// the stored state of all the buttons
uint32_t _buttons = 0;
};
example Usage in .cpp
bool VirtualJoystick::init() {
this->_buttons = 0; // Use of undeclared identifier '_buttons'
}
Hi EKLynx
IIG does not permit the declaration of member variables in the class definition. Instead, inside your CPP file you declare a structure named classname_IVars.
struct VirtualJoystick_IVars {
// the stored state of all the buttons
uint32_t _buttons = 0;
}
In your init() implementation, you allocate an instance of this structure and assign it to the ivars member. The ivars member is generated by IIG, you don't need to declare it.
bool VirtualJoystick::init()
{
if (!super::init()) return false;
ivars = IONewZero(VirtualJoystick_IVars, 1);
if (!ivars) return false;
...
}
And remember to free it in your free() implementation:
void VirtualJoystick::free()
{
IOSafeDeleteNULL(ivars, VirtualJoystick_IVars, 1);
super::free();
}
You access your ivars from a member function like so:
ivars->_buttons = 0;
