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xHCI compatible USB host controllers(i.e. super-speed USB3 controllers) can be implemented with the Debug Capability(DbC). It presents a debug device which is fully compliant with the USB framework and provides the equivalent of a very high performance full-duplex serial link. The debug capability operation model and registers interface are defined in 7.6.8 of the xHCI specification, revision 1.1. The DbC debug device shares a root port with the xHCI host. By default, the debug capability is disabled and the root port is assigned to xHCI. When the DbC is enabled, the root port will be assigned to the DbC debug device, and the xHCI sees nothing on this port. This implementation uses a sysfs node named <dbc> under the xHCI device to manage the enabling and disabling of the debug capability. When the debug capability is enabled, it will present a debug device through the debug port. This debug device is fully compliant with the USB3 framework, and it can be enumerated by a debug host on the other end of the USB link. As soon as the debug device is configured, a TTY serial device named /dev/ttyDBC0 will be created. Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.