USB集线器类特定描述符-集线器类描述符

除过USB标准的描述符外，USB集线器也定义了一个特别的集线器类描述符。

BUSHOUND抓不到该描述符的请求。

USB集线器类描述符的结构体定义如下：

typedef struct _USB_HUB_DESCRIPTOR {
    UCHAR   bDescriptorLength;
    UCHAR   bDescriptorType;
    UCHAR   bNumberOfPorts;
    USHORT  wHubCharacteristics;
    UCHAR   bPowerOnToPowerGood;
    UCHAR   bHubControlCurrent[bNumberOfPorts];
    UCHAR   bRemoveAndPowerMask[64];
} USB_HUB_DESCRIPTOR, *PUSB_HUB_DESCRIPTOR;

• bDescriptorLength：描述符的总长度。
• bDescriptorType：描述符为类型，固定为0x29.
• bNumberOfPorts：USB集线器支持的下游端口数量。
• wHubCharacteristics：集线器HUB特性，详见后续。
• bPwrOn2PwrGood：从通电正常工作所需的时间，以2ms为单位。
• bHubControlCurrent：集线器正常工作所需的最大电流，以1mA为单位。

• DeviceRemovable:指定了各个端口是否可动态移除。0了可移除，1为不可移除。

  • BIT0:保留
  • BIT1:下游端口1是否可移除。
  • BIT2：下游端口2是否可移除。
    …
  • BITn：下游端口n是否可移除。n最大为255。

• PortPwrCtrlMask:为了兼容USB1.0所保留字段。各位应全为1，位数应是8的整数倍。

wHubCharacteristics

D1…D0: Logical Power Switching Mode
00: Ganged power switching (all ports’ power atonce)
01: Individual port power switching
1X: Reserved. Used only on 1.0 compliant hubs that implement no power switching

D2: Identifies a Compound Device
0: Hub is not part of a compound device.
1: Hub is part of a compound device.

D4…D3: Over-current Protection Mode
00: Global Over-current Protection. The hub reports over-current as a summation of all ports’ current draw, without a breakdown of individual port over-current status.
01: Individual Port Over-current Protection. The hub reports over-current on a per-port basis.
Each port has an over-current status.
1X: No Over-current Protection. This option is allowed only for bus-powered hubs that do not implement over-current protection.

D6…D5: TT Think TIme
00: TT requires at most 8 FS bit times of inter transaction gap on a full-/low-speed downstream bus.
01: TT requires at most 16 FS bit times.
10: TT requires at most 24 FS bit times.
11: TT requires at most 32 FS bit times.

D7: Port Indicators Supported
0: Port Indicators are not supported on its downstream facing ports and the PORT_INDICATOR request has no effect.
1: Port Indicators are supported on its downstream facing ports and the PORT_INDICATOR request controls the indicators. See Section 11.5.3.

D15…D8: Reserved

USB集线器类描述符示例

        ------------------- USB Hub Descriptor -----------------
bDescriptorLength        : 0x09 (9 bytes)
bDescriptorType          : 0x29 (Hub Descriptor)
bNumberOfPorts           : 0x04 (4 Ports)  Hint: Ports 0 does not exist
wHubCharacteristics      : 0x0000
 Power switching         : Ganged
 Compound device         : No
 Over-current protection : Global
 TT Think Time           : At most 8 FS bit times
 Port Indicators         : Not supported
bPowerOnToPowerGood      : 0x32 (100 ms)
bHubControlCurrent       : 0x64 (100 mA)
DeviceRemovable          : 0x00
 Bit 0                   : 0 (reserved, any value)
 Bit 1                   : 0 (Device at Port 1 is removable)
 Bit 2                   : 0 (Device at Port 2 is removable)
 Bit 3                   : 0 (Device at Port 3 is removable)
 Bit 4                   : 0 (Device at Port 4 is removable)
 Bit 5                   : 0 (unused, must be 0)
 Bit 6                   : 0 (unused, must be 0)
 Bit 7                   : 0 (unused, must be 0)
PowerControlMask         : 0xFF
Data (HexDump)           : 09 29 04 00 00 32 64 00 FF                        .)...2d..
HubIsBusPowered          : 0x00 (Self Powered)