On Thu, Nov 02, 2017 at 11:15:43AM +0200, Felipe Balbi wrote: > > Hi, > > Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> writes: > >> > 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? > > the protocol running on top is 100% vendor specific. More than likely, > we would just run kgdb on top of this, right? We really don't support > microsoft's debug architecture. Ah, I didn't know about the protocol specifics here, if it is vendor-specific, then yes, we need our own id. As the above text said "well established protocol", I assumed we implemented the same thing :) 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
