What: /sys/bus/pci/drivers/xhci_hcd/.../dbc
Date: June 2017
Contact: Lu Baolu <[email protected]>
Description:
xHCI compatible USB host controllers (i.e. super-speed
USB3 controllers) are often implemented with the Debug
Capability (DbC). It can present a debug device which
is fully compliant with the USB framework and provides
the equivalent of a very high performance full-duplex
serial link for debug purpose.
The DbC debug device shares a root port with xHCI host.
When the DbC is enabled, the root port will be assigned
to the Debug Capability. Otherwise, it will be assigned
to xHCI.
Writing "enable" to this attribute will enable the DbC
functionality and the shared root port will be assigned
to the DbC device. Writing "disable" to this attribute
will disable the DbC functionality and the shared root
port will roll back to the xHCI.
Reading this attribute gives the state of the DbC. It
can be one of the following states: disabled, enabled,
initialized, connected, configured and stalled.
What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_idVendor
Date: March 2023
Contact: Mathias Nyman <[email protected]>
Description:
This dbc_idVendor attribute lets us change the idVendor field
presented in the USB device descriptor by this xhci debug
device.
Value can only be changed while debug capability (DbC) is in
disabled state to prevent USB device descriptor change while
connected to a USB host.
The default value is 0x1d6b (Linux Foundation).
It can be any 16-bit integer.
What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_idProduct
Date: March 2023
Contact: Mathias Nyman <[email protected]>
Description:
This dbc_idProduct attribute lets us change the idProduct field
presented in the USB device descriptor by this xhci debug
device.
Value can only be changed while debug capability (DbC) is in
disabled state to prevent USB device descriptor change while
connected to a USB host.
The default value is 0x0010. It can be any 16-bit integer.
What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_bcdDevice
Date: March 2023
Contact: Mathias Nyman <[email protected]>
Description:
This dbc_bcdDevice attribute lets us change the bcdDevice field
presented in the USB device descriptor by this xhci debug
device.
Value can only be changed while debug capability (DbC) is in
disabled state to prevent USB device descriptor change while
connected to a USB host.
The default value is 0x0010. (device rev 0.10)
It can be any 16-bit integer.
What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_bInterfaceProtocol
Date: March 2023
Contact: Mathias Nyman <[email protected]>
Description:
This attribute lets us change the bInterfaceProtocol field
presented in the USB Interface descriptor by the xhci debug
device.
Value can only be changed while debug capability (DbC) is in
disabled state to prevent USB descriptor change while
connected to a USB host.
The default value is 1 (GNU Remote Debug command).
Other permissible value is 0 which is for vendor defined debug
target.
What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_poll_interval_ms
Date: February 2024
Contact: Mathias Nyman <[email protected]>
Description:
This attribute adjust the polling interval used to check for
DbC events. Unit is milliseconds. Accepted values range from 0
up to 5000. The default value is 64 ms.
This polling interval is used while DbC is enabled but has no
active data transfers.
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