Going to do

To do list

1. Develop the HID descriptor as a force feedback device; Or to ensure there at least one endpoint.
2. Try sending force feedback report to the real joystick, making it vibrate.

1. What is composite device
Composite device is defined in the USB spec as follows (usb_20.pdf 5.2.3),
"A device that has multiple interfaces controlled independently of each other is referred to as a composite device."

Using composite device, multiple functions are combined into a single device.
Ex.
- Keyboard + Mouse
- Video + USB Hard disk
- I/O device (HID + USB_bulk)

Another advantage of composite device is that it eases the device driver development.
OS assigns a separate device driver to each Interface of the composite device as follows. Therefore, a dedicated monolithic driver is not required for newly designed device; you can realize it using existing drivers.

  +----------------------------+      +----------------------
 | Composite Device           |      | Host PC
 |                            |      |
 |  Function 0 -- Interface 0 --------- Device driver A <--->
 |                            |      |
 |  Function 1 -- Interface 1 --------- Device driver B <--->
 +----------------------------+      +-----------------------

When OS has some required drivers as built-in, they are available for the composite device. These OS built-in device drivers are called as USB class driver.
"Approved Class Specification Documents" from USB.org
http://www.usb.org/developers/devclass_docs#approved

Windows have these built-in class drivers.
"USB FAQ: Introductory Level - USB Class Drivers" from MS WHDC
http://www.microsoft.com/whdc/system/bus/usb/USBFAQ_intro.mspx

Please note, available drivers for a composite device are not limited only to class drivers. Any driver can be applied, as long as it doesn't require a device class (class defined in device descriptor). For example, SiLabs USB_INT and USB_bulk drivers are also applicable for composite devices.

src: http://www.cygnal.org/ubb/Forum9/HTML/001050.html