USB_DEVICE_QUALIFIER_DESCRIPTOR structure (usbspec.h)
The USB_DEVICE_QUALIFIER_DESCRIPTOR structure is used by USB client drivers to retrieve a USB-defined device qualifier descriptor.
Syntax
typedef struct _USB_DEVICE_QUALIFIER_DESCRIPTOR {
UCHAR bLength;
UCHAR bDescriptorType;
USHORT bcdUSB;
UCHAR bDeviceClass;
UCHAR bDeviceSubClass;
UCHAR bDeviceProtocol;
UCHAR bMaxPacketSize0;
UCHAR bNumConfigurations;
UCHAR bReserved;
} USB_DEVICE_QUALIFIER_DESCRIPTOR, *PUSB_DEVICE_QUALIFIER_DESCRIPTOR;
Members
bLength
Specifies the length, in bytes, of this descriptor.
bDescriptorType
Specifies the descriptor type. Must be set to USB_DEVICE_QUALIFIER_DESCRIPTOR_TYPE.
bcdUSB
Identifies the version of the USB specification that this descriptor structure complies with. This value is a binary-coded decimal number.
bDeviceClass
Specifies the class code of the device as assigned by the USB specification group.
bDeviceSubClass
Specifies the subclass code of the device as assigned by the USB specification group.
bDeviceProtocol
Specifies the protocol code of the device as assigned by the USB specification group.
bMaxPacketSize0
Specifies the maximum packet size, in bytes, for endpoint zero of the device. The value must be set to 8, 16, 32, or 64.
bNumConfigurations
Specifies the total number of possible configurations for the device.
bReserved
Reserved.
Remarks
This structure is similar to USB_DEVICE_DESCRIPTOR, but it contains only those members that can change when the device switches from full-speed operation to high-speed operation or vice versa. If the device is operating at full speed, querying for this descriptor will contain information about how the device would operate at high-speed. If, on the other hand, the device is operating at high-speed, this descriptor will contain information about how the device would operate at full-speed.
Requirements
| Requirement | Value |
|---|---|
| Header | usbspec.h (include Usb200.h) |