1 What: /sys/bus/pci/drivers/xhci_hcd/ 1 What: /sys/bus/pci/drivers/xhci_hcd/.../dbc
2 Date: June 2017 2 Date: June 2017
3 Contact: Lu Baolu <baolu.lu@linux.intel. 3 Contact: Lu Baolu <baolu.lu@linux.intel.com>
4 Description: 4 Description:
5 xHCI compatible USB host contr 5 xHCI compatible USB host controllers (i.e. super-speed
6 USB3 controllers) are often im 6 USB3 controllers) are often implemented with the Debug
7 Capability (DbC). It can prese 7 Capability (DbC). It can present a debug device which
8 is fully compliant with the US 8 is fully compliant with the USB framework and provides
9 the equivalent of a very high 9 the equivalent of a very high performance full-duplex
10 serial link for debug purpose. 10 serial link for debug purpose.
11 11
12 The DbC debug device shares a 12 The DbC debug device shares a root port with xHCI host.
13 When the DbC is enabled, the r 13 When the DbC is enabled, the root port will be assigned
14 to the Debug Capability. Other 14 to the Debug Capability. Otherwise, it will be assigned
15 to xHCI. 15 to xHCI.
16 16
17 Writing "enable" to this attri 17 Writing "enable" to this attribute will enable the DbC
18 functionality and the shared r 18 functionality and the shared root port will be assigned
19 to the DbC device. Writing "di 19 to the DbC device. Writing "disable" to this attribute
20 will disable the DbC functiona 20 will disable the DbC functionality and the shared root
21 port will roll back to the xHC 21 port will roll back to the xHCI.
22 22
23 Reading this attribute gives t 23 Reading this attribute gives the state of the DbC. It
24 can be one of the following st 24 can be one of the following states: disabled, enabled,
25 initialized, connected, config 25 initialized, connected, configured and stalled.
26 26
27 What: /sys/bus/pci/drivers/xhci_hcd/ 27 What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_idVendor
28 Date: March 2023 28 Date: March 2023
29 Contact: Mathias Nyman <mathias.nyman@li 29 Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
30 Description: 30 Description:
31 This dbc_idVendor attribute le 31 This dbc_idVendor attribute lets us change the idVendor field
32 presented in the USB device de 32 presented in the USB device descriptor by this xhci debug
33 device. 33 device.
34 Value can only be changed whil 34 Value can only be changed while debug capability (DbC) is in
35 disabled state to prevent USB 35 disabled state to prevent USB device descriptor change while
36 connected to a USB host. 36 connected to a USB host.
37 The default value is 0x1d6b (L 37 The default value is 0x1d6b (Linux Foundation).
38 It can be any 16-bit integer. 38 It can be any 16-bit integer.
39 39
40 What: /sys/bus/pci/drivers/xhci_hcd/ 40 What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_idProduct
41 Date: March 2023 41 Date: March 2023
42 Contact: Mathias Nyman <mathias.nyman@li 42 Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
43 Description: 43 Description:
44 This dbc_idProduct attribute l 44 This dbc_idProduct attribute lets us change the idProduct field
45 presented in the USB device de 45 presented in the USB device descriptor by this xhci debug
46 device. 46 device.
47 Value can only be changed whil 47 Value can only be changed while debug capability (DbC) is in
48 disabled state to prevent USB 48 disabled state to prevent USB device descriptor change while
49 connected to a USB host. 49 connected to a USB host.
50 The default value is 0x0010. I 50 The default value is 0x0010. It can be any 16-bit integer.
51 51
52 What: /sys/bus/pci/drivers/xhci_hcd/ 52 What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_bcdDevice
53 Date: March 2023 53 Date: March 2023
54 Contact: Mathias Nyman <mathias.nyman@li 54 Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
55 Description: 55 Description:
56 This dbc_bcdDevice attribute l 56 This dbc_bcdDevice attribute lets us change the bcdDevice field
57 presented in the USB device de 57 presented in the USB device descriptor by this xhci debug
58 device. 58 device.
59 Value can only be changed whil 59 Value can only be changed while debug capability (DbC) is in
60 disabled state to prevent USB 60 disabled state to prevent USB device descriptor change while
61 connected to a USB host. 61 connected to a USB host.
62 The default value is 0x0010. ( 62 The default value is 0x0010. (device rev 0.10)
63 It can be any 16-bit integer. 63 It can be any 16-bit integer.
64 64
65 What: /sys/bus/pci/drivers/xhci_hcd/ 65 What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_bInterfaceProtocol
66 Date: March 2023 66 Date: March 2023
67 Contact: Mathias Nyman <mathias.nyman@li 67 Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
68 Description: 68 Description:
69 This attribute lets us change 69 This attribute lets us change the bInterfaceProtocol field
70 presented in the USB Interface 70 presented in the USB Interface descriptor by the xhci debug
71 device. 71 device.
72 Value can only be changed whil 72 Value can only be changed while debug capability (DbC) is in
73 disabled state to prevent USB 73 disabled state to prevent USB descriptor change while
74 connected to a USB host. 74 connected to a USB host.
75 The default value is 1 (GNU R 75 The default value is 1 (GNU Remote Debug command).
76 Other permissible value is 0 w 76 Other permissible value is 0 which is for vendor defined debug
77 target. 77 target.
78 78
79 What: /sys/bus/pci/drivers/xhci_hcd/ 79 What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_poll_interval_ms
80 Date: February 2024 80 Date: February 2024
81 Contact: Mathias Nyman <mathias.nyman@li 81 Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
82 Description: 82 Description:
83 This attribute adjust the poll 83 This attribute adjust the polling interval used to check for
84 DbC events. Unit is millisecon 84 DbC events. Unit is milliseconds. Accepted values range from 0
85 up to 5000. The default value 85 up to 5000. The default value is 64 ms.
86 This polling interval is used 86 This polling interval is used while DbC is enabled but has no
87 active data transfers. 87 active data transfers.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.