linux usb简介

时间：2014-06-27 00:45:50 阅读：515 评论：0 收藏：0 [点我收藏+]

参考书：《linux device drivers》、《usb 2.0规范》《usb3.1规范》《usb白皮书》

以linux为例来说明usb系统。

先看一下usb蓝牙适配器的详细信息：

$ lsusb | grep Cambridge
Bus 001 Device 006: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)
$ sudo lsusb -s 001:006 -v
[sudo] password for host: 

Bus 001 Device 006: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass          224 Wireless
  bDeviceSubClass         1 Radio Frequency
  bDeviceProtocol         1 Bluetooth
  bMaxPacketSize0        64
  idVendor           0x0a12 Cambridge Silicon Radio, Ltd
  idProduct          0x0001 Bluetooth Dongle (HCI mode)
  bcdDevice           88.91
  iManufacturer           0 
  iProduct                2 CSR8510 A10
  iSerial                 0 
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength          177
    bNumInterfaces          2
    bConfigurationValue     1
    iConfiguration          0 
    bmAttributes         0xe0
      Self Powered
      Remote Wakeup
    MaxPower              100mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           3
      bInterfaceClass       224 Wireless
      bInterfaceSubClass      1 Radio Frequency
      bInterfaceProtocol      1 Bluetooth
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x02  EP 2 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x82  EP 2 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass       224 Wireless
      bInterfaceSubClass      1 Radio Frequency
      bInterfaceProtocol      1 Bluetooth
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0000  1x 0 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0000  1x 0 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       1
      bNumEndpoints           2
      bInterfaceClass       224 Wireless
      bInterfaceSubClass      1 Radio Frequency
      bInterfaceProtocol      1 Bluetooth
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0009  1x 9 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0009  1x 9 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       2
      bNumEndpoints           2
      bInterfaceClass       224 Wireless
      bInterfaceSubClass      1 Radio Frequency
      bInterfaceProtocol      1 Bluetooth
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0011  1x 17 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0011  1x 17 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       3
      bNumEndpoints           2
      bInterfaceClass       224 Wireless
      bInterfaceSubClass      1 Radio Frequency
      bInterfaceProtocol      1 Bluetooth
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0019  1x 25 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0019  1x 25 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       4
      bNumEndpoints           2
      bInterfaceClass       224 Wireless
      bInterfaceSubClass      1 Radio Frequency
      bInterfaceProtocol      1 Bluetooth
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0021  1x 33 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0021  1x 33 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       5
      bNumEndpoints           2
      bInterfaceClass       224 Wireless
      bInterfaceSubClass      1 Radio Frequency
      bInterfaceProtocol      1 Bluetooth
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0031  1x 49 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            1
          Transfer Type            Isochronous
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0031  1x 49 bytes
        bInterval               1
Device Status:     0x0001
  Self Powered

根据《linux device drivers》中的说明，一个设备可以有一个或者多个configuration（通常只有一个）,

一个configuration可以有一个或者多个interface,一个interface中可以有一个或者多个endpoint.

上面的蓝牙适配器有1个configuration,这个configuration有7个interface,每个interface有2个或者3个endpoint.

在linux驱动中usb设备驱动与interface相对应。

usb之间最基本的通信是通过endpoint完成的，endpoint之间只能向一个方向发送数据（主机到设备(即OUT endpoint)或者设备到主机(即IN endpoint))。

endpoint传输数据可以是下面四种类型之一：

(1) control endpoint: 用于存取usb设备的不通部分，可以配置设备、向设备发命令或者获取设备状态信息。

(2)interrupt endpoint: 主机向设备请求数据量较少时使用，例如键盘和鼠标

(3)bulk endpoint:用于大量数据传送。如果传送数据过大，则可能分成多个块传送

(4)isochronous endpoint:可以传送大量数据，通常用于能处理数据丢失以及固定速率传送数据的设备。

usb数据传输实际是通过packet来进行传输的，每个packet由SYNC(1个字节）、PID(1个字节）、CONTENT（不同PID可能有不同长度）和CRC(不同PID可能有不同长度）

详细的packet定义可以查看usb规范。

interface用于处理一种类型的usb连接，例如鼠标或者键盘等。前面的蓝牙适配器有多个interface,可以用来支持多个蓝牙设备。

interface还可能有alternate setting,　可以用来选择不同的interface参数值。

查看pci设备信息：

$ lspci
00:00.0 Host bridge: Intel Corporation 82G33/G31/P35/P31 Express DRAM Controller (rev 10)
00:02.0 VGA compatible controller: Intel Corporation 82G33/G31 Express Integrated Graphics Controller (rev 10)
00:1b.0 Audio device: Intel Corporation NM10/ICH7 Family High Definition Audio Controller (rev 01)
00:1c.0 PCI bridge: Intel Corporation NM10/ICH7 Family PCI Express Port 1 (rev 01)
00:1c.1 PCI bridge: Intel Corporation NM10/ICH7 Family PCI Express Port 2 (rev 01)
00:1c.2 PCI bridge: Intel Corporation NM10/ICH7 Family PCI Express Port 3 (rev 01)
00:1c.3 PCI bridge: Intel Corporation NM10/ICH7 Family PCI Express Port 4 (rev 01)
00:1d.0 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #1 (rev 01)
00:1d.1 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #2 (rev 01)
00:1d.2 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #3 (rev 01)
00:1d.3 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #4 (rev 01)
00:1d.7 USB controller: Intel Corporation NM10/ICH7 Family USB2 EHCI Controller (rev 01)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev e1)
00:1f.0 ISA bridge: Intel Corporation 82801GB/GR (ICH7 Family) LPC Interface Bridge (rev 01)
00:1f.1 IDE interface: Intel Corporation 82801G (ICH7 Family) IDE Controller (rev 01)
00:1f.2 IDE interface: Intel Corporation NM10/ICH7 Family SATA Controller [IDE mode] (rev 01)
00:1f.3 SMBus: Intel Corporation NM10/ICH7 Family SMBus Controller (rev 01)
04:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101E/RTL8102E PCI Express Fast Ethernet controller (rev 02)

安装tree:

sudo apt-get install tree

查看sysfs中所有usb设备文件：

$ tree /sys/bus/usb/devices/
/sys/bus/usb/devices/
├── 1-0:1.0 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1/1-0:1.0
├── 1-1 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1/1-1
├── 1-1:1.0 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1:1.0
├── 1-1.2 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.2
├── 1-1.2:1.0 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.2/1-1.2:1.0
├── 1-1.2:1.1 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.2/1-1.2:1.1
├── 1-1.3 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.3
├── 1-1.3:1.0 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.3/1-1.3:1.0
├── 1-1.3:1.1 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.3/1-1.3:1.1
├── 1-4 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1/1-4
├── 1-4:1.0 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1/1-4/1-4:1.0
├── 2-0:1.0 -> ../../../devices/pci0000:00/0000:00:1d.0/usb2/2-0:1.0
├── 2-2 -> ../../../devices/pci0000:00/0000:00:1d.0/usb2/2-2
├── 2-2:1.0 -> ../../../devices/pci0000:00/0000:00:1d.0/usb2/2-2/2-2:1.0
├── 3-0:1.0 -> ../../../devices/pci0000:00/0000:00:1d.1/usb3/3-0:1.0
├── 3-1 -> ../../../devices/pci0000:00/0000:00:1d.1/usb3/3-1
├── 3-1:1.0 -> ../../../devices/pci0000:00/0000:00:1d.1/usb3/3-1/3-1:1.0
├── 4-0:1.0 -> ../../../devices/pci0000:00/0000:00:1d.2/usb4/4-0:1.0
├── 5-0:1.0 -> ../../../devices/pci0000:00/0000:00:1d.3/usb5/5-0:1.0
├── usb1 -> ../../../devices/pci0000:00/0000:00:1d.7/usb1
├── usb2 -> ../../../devices/pci0000:00/0000:00:1d.0/usb2
├── usb3 -> ../../../devices/pci0000:00/0000:00:1d.1/usb3
├── usb4 -> ../../../devices/pci0000:00/0000:00:1d.2/usb4
└── usb5 -> ../../../devices/pci0000:00/0000:00:1d.3/usb5

本机蓝牙适配器连接到usb集线器，usb集线器连接到pc的一个usb口上。并且usb集线器还连接了其他的一些设备。

从上面的输出可以推测，1-1开头部分应该是usb集线器上连接的设备。

/sys/devices/pci0000\:00/0000\:00\:1d.7/usb1应该对应host controller设备，1-1对应struct usb_device.

1-1.2表示蓝牙适配器所在hub口，1-1.2:1.0和1-1.2:1.1可能分别表示蓝牙适配器的接口。

查看这两个接口的endpoint：

$ ls -d /sys/devices/pci0000\:00/0000\:00\:1d.7/usb1/1-1/1-1.2/1-1.2\:1.0/ep*
/sys/devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.2/1-1.2:1.0/ep_02  /sys/devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.2/1-1.2:1.0/ep_82
/sys/devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.2/1-1.2:1.0/ep_81

$ ls -d /sys/devices/pci0000\:00/0000\:00\:1d.7/usb1/1-1/1-1.2/1-1.2\:1.1/ep*
/sys/devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.2/1-1.2:1.1/ep_03  /sys/devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1.2/1-1.2:1.1/ep_83

1-1.2:1.0下有三个endpoint,对应与lsusb输出信息中的第一个interface中的3个endpoint.

1-1.2:1.1下有两个endpoint,对应于lsusb输出信息中的其他interface中的2个endpoint。

但是lsusb中总共有7个interface,最后6个interface只用一个interface就能表示，似乎看起来很奇怪。

仔细看上面的输出信息可以知道,最后6个interface确实是一个interface，只是使用了alterate setting,其bAlternateSetting的值分别是0-5，其它组成部分的值一模一样。

linux usb简介,布布扣,bubuko.com

linux usb简介

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原文地址：http://www.cnblogs.com/qiaoqiao2003/p/3807541.html

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