From: Lu Baolu <baolu.lu@linux.intel.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Felipe Balbi <felipe.balbi@linux.intel.com>
Cc: "'Mathias Nyman'" <mathias.nyman@linux.intel.com>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 2/3] usb: xhci: Add DbC support in xHCI driver
Date: Fri, 3 Nov 2017 08:45:46 +0800 [thread overview]
Message-ID: <59FBBC3A.3040809@linux.intel.com> (raw)
In-Reply-To: <20171102165113.GB18566@kroah.com>
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@linuxfoundation.org> writes:
>>>> > >> Greg Kroah-Hartman <gregkh@linuxfoundation.org> 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@linux.intel.com>
>>>>>>> > >> >> > ---
>>>>>>> > >> >> > .../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
next prev parent reply other threads:[~2017-11-03 0:45 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-05 1:58 [PATCH v3 0/3] usb: xhci: Add debug capability support in xhci Lu Baolu
2017-09-05 1:58 ` [PATCH v3 1/3] usb: xhci: Make some static functions global Lu Baolu
2017-09-05 1:58 ` [PATCH v3 2/3] usb: xhci: Add DbC support in xHCI driver Lu Baolu
2017-10-24 17:03 ` Mathias Nyman
2017-10-25 2:15 ` Lu Baolu
2017-11-02 1:36 ` Lu Baolu
2017-11-02 8:17 ` Greg Kroah-Hartman
2017-11-02 9:15 ` Felipe Balbi
2017-11-02 9:32 ` Greg Kroah-Hartman
2017-11-02 10:38 ` Felipe Balbi
2017-11-02 16:51 ` Greg Kroah-Hartman
2017-11-03 0:45 ` Lu Baolu [this message]
2017-11-03 6:27 ` Greg Kroah-Hartman
2017-11-03 10:52 ` Felipe Balbi
2017-11-06 0:35 ` Lu Baolu
2017-11-06 8:00 ` Greg Kroah-Hartman
2017-11-07 2:32 ` Lu Baolu
2017-11-13 15:26 ` Mathias Nyman
2017-11-14 7:28 ` Felipe Balbi
2017-11-15 7:25 ` Lu Baolu
2017-09-05 1:59 ` [PATCH v3 3/3] usb: doc: Update document for USB3 debug port usage Lu Baolu
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