On Thu, Nov 02, 2017 at 09:36:42AM +0800, Lu Baolu wrote: > Hi Greg, > > On 09/05/2017 09:58 AM, Lu Baolu wrote: > > 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. > > > > One use of this link is running a login service on the debug target. > > Hence it can be remote accessed by a debug host. Another use case can > > probably be found in servers. It provides a peer-to-peer USB link > > between two host-only machines. This provides a reasonable out-of-band > > communication method between two servers. > > > > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> > > --- > > .../ABI/testing/sysfs-bus-pci-drivers-xhci_hcd | 25 + > > drivers/usb/host/Kconfig | 9 + > > drivers/usb/host/Makefile | 5 + > > drivers/usb/host/xhci-dbgcap.c | 1016 ++++++++++++++++++++ > > drivers/usb/host/xhci-dbgcap.h | 247 +++++ > > drivers/usb/host/xhci-dbgtty.c | 586 +++++++++++ > > drivers/usb/host/xhci-trace.h | 60 ++ > > drivers/usb/host/xhci.c | 10 + > > drivers/usb/host/xhci.h | 1 + > > 9 files changed, 1959 insertions(+) > > create mode 100644 Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd > > create mode 100644 drivers/usb/host/xhci-dbgcap.c > > create mode 100644 drivers/usb/host/xhci-dbgcap.h > > create mode 100644 drivers/usb/host/xhci-dbgtty.c > > > > [snip] > > > +#define DBC_VENDOR_ID 0x1d6b /* Linux Foundation 0x1d6b */ > > +#define DBC_PRODUCT_ID 0x0004 /* device 0004 */ > > > > The DbC (xHCI DeBug Capability) is an optional functionality in > some xHCI host controllers. It will present a super-speed debug > device through the debug port after it is enabled. > > The DbC register set defines an interface for system software > to specify the vendor id and product id of the debug device. > These two values will be presented by the debug device in its > device descriptor idVendor and idProduct fields. > > Microsoft Windows have a well established protocol for > debugging over DbC. And it assigns below values for its use. > > USB\VID_045E&PID_062D.DeviceDesc="Microsoft USB Debug Target" > > I'm going to use 0x1d6b/0x0004 value pair for DbC use in > Linux. Do you approve me to do so? No. Why can't you use the same ids as Windows? This is implementing the same protocol, right? If you have to use a OS-specific id, I can give you a new one, but 0004 is not ok to use for this. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
