1*4882a593SmuzhiyunWhat: /sys/bus/pci/drivers/xhci_hcd/.../dbc 2*4882a593SmuzhiyunDate: June 2017 3*4882a593SmuzhiyunContact: Lu Baolu <baolu.lu@linux.intel.com> 4*4882a593SmuzhiyunDescription: 5*4882a593Smuzhiyun xHCI compatible USB host controllers (i.e. super-speed 6*4882a593Smuzhiyun USB3 controllers) are often implemented with the Debug 7*4882a593Smuzhiyun Capability (DbC). It can present a debug device which 8*4882a593Smuzhiyun is fully compliant with the USB framework and provides 9*4882a593Smuzhiyun the equivalent of a very high performance full-duplex 10*4882a593Smuzhiyun serial link for debug purpose. 11*4882a593Smuzhiyun 12*4882a593Smuzhiyun The DbC debug device shares a root port with xHCI host. 13*4882a593Smuzhiyun When the DbC is enabled, the root port will be assigned 14*4882a593Smuzhiyun to the Debug Capability. Otherwise, it will be assigned 15*4882a593Smuzhiyun to xHCI. 16*4882a593Smuzhiyun 17*4882a593Smuzhiyun Writing "enable" to this attribute will enable the DbC 18*4882a593Smuzhiyun functionality and the shared root port will be assigned 19*4882a593Smuzhiyun to the DbC device. Writing "disable" to this attribute 20*4882a593Smuzhiyun will disable the DbC functionality and the shared root 21*4882a593Smuzhiyun port will roll back to the xHCI. 22*4882a593Smuzhiyun 23*4882a593Smuzhiyun Reading this attribute gives the state of the DbC. It 24*4882a593Smuzhiyun can be one of the following states: disabled, enabled, 25*4882a593Smuzhiyun initialized, connected, configured and stalled. 26