USB Protocol (2) Terminology

extensible-host-controler-interface-usb-xhci.pdf
Universal Serial Bus 3.0 Specification.pdf

xHCI
	eXtensible Host Controller Interface (xHCI) 
	可扩展的 主机 控制器 接口
	describes the register-level host controller interface for Universal Serial Bus (0) Revision 2.0 and above

Root Hub
	A (tier 1) Root Hub is always presented by the xHC. Refer to section 4.19 for more information.
	xHCAlways provide（第1层）根集线器.有关更多信息,请参阅第4.19节.
Root Hub Port
	The downstream port on a Root Hub.
	The downstream end of the root hub on.

Default Control Endpoint
	The Default Control Endpoint always exists once a USB
	device is powered, in order to provide access to the device's
	configuration, status, and control information. The Default
	Control Endpoint is always endpoint number '0'.
	一旦USB设备通电,Control the endpoint always there,In order to provide the equipment configuration、State and control the access of information.
	Control the endpoint is always the endpoint number“0”.

Device Context Base Address Array
	The Device Context Base Address Array contains 256
	entries and supports up to 255 USB devices or hubs, where
	each element in the array is a 64-bit pointer to the base
	address of a Device Context. Entry 0 is reserved.
	Of the device context array contains256个条目(数组),最多支持255个USBEquipment or hub.Each device has an array,(Each member of the array to store the different context of b)
	In which each element of the array is a64位指针,Pointing device context b
	条目0已保留. // 条目0 ??
	
Device Context
	A Device Context is a data structure that describes an
	individual USB device attached to the host controller. A
	Device Context is organized as an array of up to 32 context
	data structures, consisting of 1 Slot Context and up to 31
	Endpoint Context data structures.
	
	Device context is connected to the host controller of singleUSB设备的数据结构.
	
	Device context organization for as many as32A context data structure of the array,由1A slot context, and as many as31An endpoint context data structure.
	
	In the middle of each array up to32个成员.Each member to the structure of the body 为 32 个字节(该32个字节为 context data structure)

Dequeue Pointer
	The Dequeue Pointer is a pointer into a TRB Ring. It
	references the next TRB in a TRB Ring to be processed by
	the consumer of TRB Ring work items. The Dequeue
	Pointer for Transfer and Command Rings is NOT defined as
	a physical xHC register. A facsimile of this pointer is
	maintained internally by the xHC and system software to
	manage a respective ring.
	
	Dequeue pointer is pointing to theTRBA pointer to the ring.
	它引用TRBRing up toTRBRing work items users deal with the nextTRB.
	Transmission loop and command loop dequeue pointer is not defined as physicalxHC寄存器.
	xHCInternal maintenance and system software in the pointer fax,To manage the corresponding ring.

Enqueue Pointer
	The Enqueue Pointer is a pointer into a TRB Ring. It
	references the next TRB location available to producer for
	scheduling work items to the Ring. The Enqueue Pointer is
	NOT defined as a physical xHC register. A facsimile of this
	pointer is maintained internally by the xHC and system
	software to manage a respective ring.

	Queue pointer is pointing to theTRBA pointer to the ring.
	It refers to the producer can be used to the work item scheduling to ring the nextTRB位置.
	Queue pointer is not defined as physicalxHC寄存器.
	xHCInternal maintenance and system software in the pointer fax,To manage the corresponding ring.


Transfer Request Block(TRB)
	A TRB is a small, flexible data structure in memory that
	defines the characteristics of a single DMA operation
	executed by the xHC.

Transfer Ring
	A Transfer Ring is a TRB Ring associated with an Endpoint
	Context. Each Transfer Ring describes the scheduled work
	items for a single USB Endpoint.
Transfer Type
	Determines the characteristics of the data flow between a
	software client and its function. Four standard transfer
	types are defined: control, interrupt, bulk, and isochronous.

TRB Ring
	A TRB Ring is defined by three parameters: 
		a pointer to the TRB Ring data structure base address, 
		and Enqueue Pointers that define the “active” TRBs in the ring
		and Dequeue Pointers that define the “active” TRBs in the ring.

TBR 种类
	Event Data TRB
		A Normal Transfer TRB with its Event Data (ED) flag equal to ‘1’. Refer to section 4.11.5.2.
	Isoch TRB
		An Isochronous Transfer Request Block that is always the
		first TRB of an Isoch TD. They are only found on the
		Transfer Rings associated with Isoch Endpoints. Refer to
		section 4.11.2.3.

	Link TRB
		A Transfer Request Block that is always the last TRB of a
		TRB Ring Segment. Link TRBs are used to form large, non-
		contiguous Transfer Rings that cross Page boundaries.
		Refer to section 4.11.5.1.
	Normal TRB
		A Normal Transfer Request Block that is used on transfer
		Rings to define a single contiguous buffer for a data
		transfer. Normal TRBs may be “chained” to support
		scatter/gather or buffer concatenation operations. Refer to
		section 4.11.2.1.
	Setup Stage TRB
		A Setup Stage Transfer Request Block that is always the
		first TRB of a Setup Stage TD. They are only found on the
		Transfer Rings associated with Control Endpoints. Refer to
		section 4.11.2.2.