The bDescriptorType field is a number value from the USB CCID descriptor: Functional Descriptor type.
| bDescriptorType | # | % |
|---|---|---|
| 0x21 | 249 | 98.03 % |
| 0xFF | 5 | 1.97 % |
The CCID 1.1 specification gives/imposes the value 21h. FFh is for proprietary devices.
It is then not suprising that thevast majority of devices use the standardized value 21h.
The 5 devices with bDescriptorType = 0xFF are:
- Dell keyboard SK-3106
- Gemalto Gem e-Seal Pro USB Token
- MYSMART MySMART PAD V2.0
- Verisign Secure Storage Token
- Verisign Secure Token