The !usb3kd.xhci_commandring extension displays information about the command ring data structure associated with a USB 3.0 host controller.

!usb3kd.xhci_commandring DeviceExtension


AAddress of the device extension for the host controller's functional device object (FDO).




The output the !xhci_commandring command is based on the data structures maintained by the USB 3.0 host controller driver (UsbXhci.sys). For more information about the USB 3.0 host controller driver and other drivers in the USB stack, see USB Driver Stack Architecture.

The command ring is a data structure used by the USB 3.0 host controller driver to pass commands to the host controller.


To obtain the address of the device extension, look at the output of the !xhci_dumpall command. In the following example, the address of the device extension is 0xfffffa800536e2d0.

3: kd> !xhci_dumpall

## Dumping all the XHCI controllers - DrvObj 0xfffffa80053072f0
1)  ... - PCI: VendorId ... DeviceId ... RevisionId ... Firmware ...

    dt USBXHCI!_CONTROLLER_DATA 0xfffffa80052f20c0
    !rcdrlogdump USBXHCI -a 0xfffffa8005068520
    !rcdrlogdump USBXHCI -a 0xfffffa8004e8b9a0 (rundown)
    !wdfdevice 0x57ffac91fd8
    !xhci_capability 0xfffffa800536e2d0
    !xhci_registers 0xfffffa800536e2d0
    !xhci_commandring 0xfffffa800536e2d0 (No commands are pending)

Now you can pass the address of the device extension to the !xhci_commandring command.

3: kd> !xhci_commandring 0xfffffa800536e2d0

## Dumping dt _COMMAND_DATA 0xfffffa8005362f70 !rcdrlogdump USBXHCI -a 0xfffffa8005a8f010
Stop: OFF Abort: OFF Running: ON
CommandRingBufferData: VA 0xfffffa8005aeb200 LA 0x1168eb200 !wdfcommonbuffer 0x57ffa65d988 Size 512
DequeueIndex: 24 EnqueueIndex: 24 CycleState: 0

    Command Ring TRBs:
        [  0] Unknown TRB Type 49 0xfffffa8005aeb200

        [  1] ENABLE_SLOT                 0xfffffa8005aeb210 CycleBit 1
        [  2] ADDRESS_DEVICE              0xfffffa8005aeb220 CycleBit 1 SlotId  1 BlockSetAddressRequest 1

        Empty List

        Empty List

See also

USB 3.0 Extensions


Universal Serial Bus (USB) Drivers

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