/sys/kernel/debug/usb/devices解析

1.概述

USB设备通过debugfs导出/sys/kernel/debug/usb/devices显示内核已知的每个USB设备及其配置描述符。此文件对于用户模式下的状态查看
工具非常方便，可以扫描文本格式并忽略大部分文本。设备特定文件中提供了更详细的设备状态（包括类和供应商状态）。

此文件与poll()系统调用结合使用，还可用于检测何时添加或删除设备：

int fd;
struct pollfd pfd;

fd = open("/sys/kernel/debug/usb/devices", O_RDONLY);
pfd = { fd, POLLIN, 0 };
for (;;) {
    /* The first time through, this call will return immediately. */
    poll(&pfd, 1, -1);

    /* To see what's changed, compare the file's previous and current
       contents or scan the filesystem.  (Scanning is more precise.) */
}

请注意，此行为旨在用于信息获取和调试目的。例如，使用诸如udev或HAL之类的程序来初始化设备或启动用户模式助手程序会更合适。

2.文件格式
每个T：行（拓扑信息：Lev，Prnt，Port，Cnt）的前4列中的数字可用于构建USB拓扑图。
每行标记有该行的单字符ID：

T = Topology (etc.)
B = Bandwidth (applies only to USB host controllers, which are virtualized as root hubs)
D = Device descriptor info.
P = Product ID info. (from Device descriptor, but they won't fit together on one line)
S = String descriptors.
C = Configuration descriptor info. (* = active configuration)
I = Interface descriptor info.
E = Endpoint descriptor info.

历史遗留：d = 十进制数（可能有前导空格或0） x = 十六进制数（可能有前导空格或0） s = string

1）拓扑信息：

T:  Bus=dd Lev=dd Prnt=dd Port=dd Cnt=dd Dev#=ddd Spd=dddd MxCh=dd
|   |      |      |       |       |      |        |        |__MaxChildren
|   |      |      |       |       |      |        |__Device Speed in Mbps
|   |      |      |       |       |      |__DeviceNumber
|   |      |      |       |       |__Count of devices at this level
|   |      |      |       |__Connector/Port on Parent for this device
|   |      |      |__Parent DeviceNumber
|   |      |__Level in topology for this bus
|   |__Bus number
|__Topology info tag

Speed如下，插入端口4的设备将显示Port = 03。

1.5 Mbit/s for low speed USB
12  Mbit/s for full speed USB
480 Mbit/s for high speed USB (added for USB 2.0); also used for Wireless USB, which has no fixed speed
5000 Mbit/s for SuperSpeed USB (added for USB 3.0)

2）带宽信息：

B:  Alloc=ddd/ddd us (xx%), #Int=ddd, #Iso=ddd
|   |                       |         |__Number of isochronous requests
|   |                       |__Number of interrupt requests
|   |__Total Bandwidth allocated to this bus
|__Bandwidth info tag

3）设备描述符信息和产品ID信息：

D:  Ver=x.xx Cls=xx(s) Sub=xx Prot=xx MxPS=dd #Cfgs=dd
P:  Vendor=xxxx ProdID=xxxx Rev=xx.xx

D:  Ver=x.xx Cls=xx(sssss) Sub=xx Prot=xx MxPS=dd #Cfgs=dd
|   |        |             |      |       |       |__NumberConfigurations
|   |        |             |      |       |__MaxPacketSize of Default Endpoint
|   |        |             |      |__DeviceProtocol
|   |        |             |__DeviceSubClass
|   |        |__DeviceClass
|   |__Device USB version
|__Device info tag #1

P:  Vendor=xxxx ProdID=xxxx Rev=xx.xx
|   |           |           |__Product revision number
|   |           |__Product ID code
|   |__Vendor ID code
|__Device info tag #2

4）字符串描述符信息：

S:  Manufacturer=ssss
|   |__Manufacturer of this device as read from the device.
|      For USB host controller drivers (virtual root hubs) this may
|      be omitted, or (for newer drivers) will identify the kernel
|      version and the driver which provides this hub emulation.
|__String info tag

S:  Product=ssss
|   |__Product description of this device as read from the device.
|      For older USB host controller drivers (virtual root hubs) this
|      indicates the driver; for newer ones, it's a product (and vendor)
|      description that often comes from the kernel's PCI ID database.
|__String info tag

S:  SerialNumber=ssss
|   |__Serial Number of this device as read from the device.
|      For USB host controller drivers (virtual root hubs) this is
|      some unique ID, normally a bus ID (address or slot name) that
|      can't be shared with any other device.
|__String info tag

5）配置描述符信息：

C:* #Ifs=dd Cfg#=dd Atr=xx MPwr=dddmA
| | |       |       |      |__MaxPower in mA
| | |       |       |__Attributes
| | |       |__ConfiguratioNumber
| | |__NumberOfInterfaces
| |__ "*" indicates the active configuration (others are " ")
|__Config info tag

USB设备可能具有多种配置，每种配置的行为都不同。例如，总线供电的配置可能比自供电配置的能力低得多。一次只能激活一个设备配
置; 大多数设备只有一个配置。
每个配置都包含一个或多个接口。每个接口都提供不同的“功能”，通常绑定到不同的USB设备驱动程序。一个常见的例子是带有用于回放的
音频接口的USB扬声器，以及用于软件音量控制的HID接口。

:6）接口描述符信息：

I:* If#=dd Alt=dd #EPs=dd Cls=xx(sssss) Sub=xx Prot=xx Driver=ssss
| | |      |      |       |             |      |       |__Driver name
| | |      |      |       |             |      |          or "(none)"
| | |      |      |       |             |      |__InterfaceProtocol
| | |      |      |       |             |__InterfaceSubClass
| | |      |      |       |__InterfaceClass
| | |      |      |__NumberOfEndpoints
| | |      |__AlternateSettingNumber
| | |__InterfaceNumber
| |__ "*" indicates the active altsetting (others are " ")
|__Interface info tag

一个给定接口可以具有一个或多个“可选”设置。例如，默认设置可能不会使用少量的周期性带宽。要使用大部分总线带宽，驱动程序必须
选择非默认的altsetting。
一次只能有一个接口的设置处于活动状态，并且一次只能有一个驱动程序绑定到接口。大多数设备每个接口只有一个可用设置。

7）端点描述符信息：

E:  Ad=xx(s) Atr=xx(ssss) MxPS=dddd Ivl=dddss
|   |        |            |         |__Interval (max) between transfers
|   |        |            |__EndpointMaxPacketSize
|   |        |__Attributes(EndpointType)
|   |__EndpointAddress(I=In,O=Out)
|__Endpoint info tag

所有周期性（中断或等时）端点的间隔都是非零的。对于高速端点，传输间隔可以以微秒而不是毫秒来度量。
对于高速周期端点，EndpointMaxPacketSize反映了每微帧数据传输大小。对于“高带宽”端点，每个端点可以反映两个或三个数据包（每125
个用户最多3个字节）。
使用Linux-USB堆栈，定期带宽保留使用URB提供的传输间隔和大小，这可能小于端点描述符中的传输间隔和大小。

3.此文件的使用例子

例如，如果用户或脚本仅对拓扑信息感兴趣，请使用类似的内容

grep ^T: /sys/kernel/debug/usb/devices 仅用于拓扑行。
grep -i ^[tdp]: /sys/kernel/debug/usb/devices 这样的命令可用于仅列出以方括号中的字符开头的行，其中有效字符为TDPCIE。使用稍
微更强大的脚本，它可以显示任何选定的行（例如，只显示T，D和P行）并更改其输出格式。（procusb Perl脚本是这个想法的开始。它将
仅列出从/sys/kernel/debug/usb/devices中选择的行[从TBDPSCIE中选择]或“All”行。）

拓扑行可用于生成系统根集线器上USB设备的图形/图示。
接口行可用于确定每个设备使用的驱动程序，以及被激活的可选设置。
配置行可用于列出系统的USB设备正在使用的最大功率（以毫安为单位）。例如:/sys/kernel/debug/usb/devices.

eg:

T:  Bus=00 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12   MxCh= 2
B:  Alloc= 28/900 us ( 3%), #Int=  2, #Iso=  0
D:  Ver= 1.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=0000 ProdID=0000 Rev= 0.00
S:  Product=USB UHCI Root Hub
S:  SerialNumber=dce0
C:* #Ifs= 1 Cfg#= 1 Atr=40 MxPwr=  0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   8 Ivl=255ms

T:  Bus=00 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  2 Spd=12   MxCh= 4
D:  Ver= 1.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=0451 ProdID=1446 Rev= 1.00
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   1 Ivl=255ms

T:  Bus=00 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#=  3 Spd=1.5  MxCh= 0
D:  Ver= 1.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=04b4 ProdID=0001 Rev= 0.00
C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=01 Prot=02 Driver=mouse
E:  Ad=81(I) Atr=03(Int.) MxPS=   3 Ivl= 10ms

T:  Bus=00 Lev=02 Prnt=02 Port=02 Cnt=02 Dev#=  4 Spd=12   MxCh= 0
D:  Ver= 1.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=0565 ProdID=0001 Rev= 1.08
S:  Manufacturer=Peracom Networks, Inc.
S:  Product=Peracom USB to Serial Converter
C:* #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 3 Cls=00(>ifc ) Sub=00 Prot=00 Driver=serial
E:  Ad=81(I) Atr=02(Bulk) MxPS=  64 Ivl= 16ms
E:  Ad=01(O) Atr=02(Bulk) MxPS=  16 Ivl= 16ms
E:  Ad=82(I) Atr=03(Int.) MxPS=   8 Ivl=  8ms

从中选择仅T：和I：行（例如，使用procusb ti），我们有:

T:  Bus=00 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12   MxCh= 2
T:  Bus=00 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  2 Spd=12   MxCh= 4  接在父设备的0号端口上， 而且自己有4个下行端口
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
T:  Bus=00 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#=  3 Spd=1.5  MxCh= 0
I:  If#= 0 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=01 Prot=02 Driver=mouse
T:  Bus=00 Lev=02 Prnt=02 Port=02 Cnt=02 Dev#=  4 Spd=12   MxCh= 0 接在父设备的2号端口上，自己没有下行端口
I:  If#= 0 Alt= 0 #EPs= 3 Cls=00(>ifc ) Sub=00 Prot=00 Driver=serial

得出拓扑：

                    +------------------+
                    |  PC/root_hub (12)|   Dev# = 1
                    +------------------+   (nn) is Mbps.
  Level 0           |  CN.0   |  CN.1  |   [CN = connector/port #]
                    +------------------+
                        /
                       /
          +-----------------------+
Level 1   | Dev#2: 4-port hub (12)|
          +-----------------------+
          |CN.0 |CN.1 |CN.2 |CN.3 |
          +-----------------------+
              \           \____________________
               \_____                          \
                     \                          \
             +--------------------+      +--------------------+
Level 2      | Dev# 3: mouse (1.5)|      | Dev# 4: serial (12)|
             +--------------------+      +--------------------+

下面是我这个Renesas开发板的：

# cat /sys/kernel/debug/usb/devices 

T:  Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480  MxCh= 1
B:  Alloc=  0/800 us ( 0%), #Int=  0, #Iso=  0
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0002 Rev= 4.14
S:  Manufacturer=Linux 4.14.35 ehci_hcd
S:  Product=EHCI Host Controller
S:  SerialNumber=ee080100.usb
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=  0mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   4 Ivl=256ms

T:  Bus=02 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480  MxCh= 1
B:  Alloc=  0/800 us ( 0%), #Int=  0, #Iso=  0
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0002 Rev= 4.14
S:  Manufacturer=Linux 4.14.35 ehci_hcd
S:  Product=EHCI Host Controller
S:  SerialNumber=ee0a0100.usb
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=  0mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   4 Ivl=256ms

T:  Bus=03 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12   MxCh= 1
B:  Alloc=  0/900 us ( 0%), #Int=  0, #Iso=  0
D:  Ver= 1.10 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0001 Rev= 4.14
S:  Manufacturer=Linux 4.14.35 ohci_hcd
S:  Product=Generic Platform OHCI controller
S:  SerialNumber=ee080000.usb
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=  0mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   2 Ivl=255ms

T:  Bus=04 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12   MxCh= 1
B:  Alloc=  0/900 us ( 0%), #Int=  0, #Iso=  0
D:  Ver= 1.10 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0001 Rev= 4.14
S:  Manufacturer=Linux 4.14.35 ohci_hcd
S:  Product=Generic Platform OHCI controller
S:  SerialNumber=ee0a0000.usb
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=  0mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   2 Ivl=255ms

https://01.org/linuxgraphics/gfx-docs/drm/driver-api/usb/usb.html#dev-bus-usb-bbb-ddd

posted on 2018-08-04 16:02 Hello-World3 阅读(3705) 评论(0) 编辑收藏举报

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