Hi Xenia, Thanks for looking into this. On Thu, May 29, 2014 at 6:31 PM, Xenia Ragiadakou <burzalodowa@xxxxxxxxx> wrote: > I misunderstood the following description regarding the slot id field of > Command Completion Event TRB: > > "The Slot ID field shall be updated by the xHC to reflect the slot > associated with the > command that generated the event, with the following exceptions: > - The Slot ID shall be cleared to ‘0’ for No Op, Set Latency Tolerance > Value, Get Port > Bandwidth, and Force Event Commands. > - The Slot ID shall be set to the ID of the newly allocated Device Slot for > the Enable Slot > Command. > - The value of Slot ID shall be vendor defined when generated by a vendor > defined command. > This value is used as an index in the Device Context Base Address Array to > select the Device > Context of the source device. If this Event is due to a Host Controller > Command, then this field > shall be cleared to ‘0’." > > The xhci spec rev1.0, for the Stop Endpoint Command, the Set TR Dequeue > Pointer Command and the Reset Endpoint Command, states explicitely that the > Command Completion Event placed on the Event Ring by the xHC shall have > initialized the Slot ID field to the value of the command’s Slot ID. > However, regarding the Reset Device Command it states that this field should > be cleared to zero. So, it was my mistake and your hardware is compatible > with the spec. > While the spec appears to be unambiguous about Slot ID for Reset Device event TRB (always 0), in the case of Set TR Dequeue Pointer Command, Section 4.6.10 says (in xHCI rev 1.1 - is rev 1.0 similar?): "To issue a Set TR Dequeue Pointer Command system software shall perform the following operations: ... Write the Host Controller Doorbell with DB Target = Host Controller Command ... When a Set TR Dequeue Pointer Command is executed by the xHC it shall perform the following operations: ... Slot ID = The value of the command?s Slot ID. ..." So, when xHC writes a Set TR Dequeue Pointer Command Completion Event on the ring, there seem to be two different, possibly contradictory, ways to do it: 1. Following 4.6.10, "Slot ID = The value of the command?s Slot ID." 2. Following your quoted block of text from 6.4.2.2, "If this Event is due to a Host Controller Command, then this (Slot ID) field shall be cleared to 0" Both statements use 'shall', which according Word Usage is the new 'must'. Is there a Section-wise precedence order for cases like this? The other two commands - Stop Endpoint Command and Reset Endpoint Command are also subject to the same conundrum, if indeed there is one. If I'm mistaken, the email + patch I sent yesterday should be ignored: http://www.spinics.net/lists/linux-usb/msg108566.html -- 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
