Hi, On 11/03/2017 12:51 AM, Greg Kroah-Hartman wrote: > On Thu, Nov 02, 2017 at 12:38:57PM +0200, Felipe Balbi wrote: >> > >> > Hi, >> > >> > Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> writes: >>>> > >> 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. >> > >> > Great, thanks :-) >> > >> > Let us know which one we're allowed to use and I'm sure Baolu can respin >> > the patch in no time. > Can I get a "full" description of what string this device id will > reference? Is it "Linux USB Debug Target" or something else? > Current manufacturer and product strings are set like this. +#define DBC_STRING_MANUFACTURER "Linux" +#define DBC_STRING_PRODUCT "Remote GDB" These are also place holders. We can change them to more meaningful strings. Best regards, Lu Baolu -- 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