2 Commits

Author SHA1 Message Date
Mathias Nyman
edf1664f32 xhci: dbc: Provide sysfs option to configure dbc descriptors
When DbC is enabled the first port on the xHC host acts as a usb device.
xHC provides the descriptors automatically when the DbC device is
enumerated. Most of the values are hardcoded, but some fields such as
idProduct, idVendor, bcdDevice and bInterfaceProtocol can be modified.

Add sysfs entries that allow userspace to change these.
User can only change them before dbc is enabled, i.e. before writing
"enable" to dbc sysfs file as we don't want these values to change while
device is connected, or during  enumeration.

Add documentation for these entries in
Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20230317154715.535523-9-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-03-23 17:25:22 +01:00
Lu Baolu
dfba2174dc usb: xhci: Add DbC support in xHCI driver
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>
2017-12-08 17:43:52 +01:00