2.7 usb攝像頭之usb攝像頭描述符打印

學習目標：參考lsusb源碼，打印USB攝像頭的設備描述符、配置描述符、接口聯合描述符、端點描述符；

1、lsusb命令和源碼

使用命令lsusb能夠看看設備的id，並執行 # lsusb -v -d 0x1b3b:2977 命令查看usb攝像頭的描述符。

2、源碼

打印如下描述符：

程序主要正在probe執行printk函數進行打印：

  1 static int myuvc_probe(struct usb_interface *intf,
  2              const struct usb_device_id *id)
  3 {
  4     static int cnt = 0;
  5     struct usb_device *dev = interface_to_usbdev(intf);
  6     struct usb_device_descriptor *descriptor = &dev->descriptor;
  7     struct usb_host_config *hostconfig;
  8     struct usb_config_descriptor *config;
  9     struct usb_interface_assoc_descriptor *assoc_desc;
 10     struct usb_interface_descriptor    *interface;
 11     struct usb_endpoint_descriptor  *endpoint;
 12     int i, j, k, l, m;
 13     unsigned char *buffer;
 14     int buflen;
 15     int desc_len;
 16     int desc_cnt;
 17 
 18     printk("myuvc_probe : cnt = %d\n", cnt++);
 19 
 20     /* 打印設備描述符 */
 21     printk("Device Descriptor:\n"
 22            "  bLength             %5u\n"
 23            "  bDescriptorType     %5u\n"
 24            "  bcdUSB              %2x.%02x\n"
 25            "  bDeviceClass        %5u \n"
 26            "  bDeviceSubClass     %5u \n"
 27            "  bDeviceProtocol     %5u \n"
 28            "  bMaxPacketSize0     %5u\n"
 29            "  idVendor           0x%04x \n"
 30            "  idProduct          0x%04x \n"
 31            "  bcdDevice           %2x.%02x\n"
 32            "  iManufacturer       %5u\n"
 33            "  iProduct            %5u\n"
 34            "  iSerial             %5u\n"
 35            "  bNumConfigurations  %5u\n",
 36            descriptor->bLength, descriptor->bDescriptorType,
 37            descriptor->bcdUSB >> 8, descriptor->bcdUSB & 0xff,
 38            descriptor->bDeviceClass, 
 39            descriptor->bDeviceSubClass,
 40            descriptor->bDeviceProtocol, 
 41            descriptor->bMaxPacketSize0,
 42            descriptor->idVendor,  descriptor->idProduct,
 43            descriptor->bcdDevice >> 8, descriptor->bcdDevice & 0xff,
 44            descriptor->iManufacturer, 
 45            descriptor->iProduct, 
 46            descriptor->iSerialNumber, 
 47            descriptor->bNumConfigurations);
 48 
 49     for (i = 0; i < descriptor->bNumConfigurations; i++)
 50     {
 51         hostconfig = &dev->config[i]; //第i個配置
 52         config     = &hostconfig->desc;
 53         printk("  Configuration Descriptor %d:\n"
 54                "    bLength             %5u\n"
 55                "    bDescriptorType     %5u\n"
 56                "    wTotalLength        %5u\n"
 57                "    bNumInterfaces      %5u\n"
 58                "    bConfigurationValue %5u\n"
 59                "    iConfiguration      %5u\n"
 60                "    bmAttributes         0x%02x\n",
 61                i, 
 62                config->bLength, config->bDescriptorType,
 63                le16_to_cpu(config->wTotalLength),
 64                config->bNumInterfaces, config->bConfigurationValue,
 65                config->iConfiguration,
 66                config->bmAttributes);
 67         
 68         assoc_desc = hostconfig->intf_assoc[0]; //IAD 
 69         printk("    Interface Association:\n"
 70                "      bLength             %5u\n"
 71                "      bDescriptorType     %5u\n"
 72                "      bFirstInterface     %5u\n"
 73                "      bInterfaceCount     %5u\n"
 74                "      bFunctionClass      %5u\n"
 75                "      bFunctionSubClass   %5u\n"
 76                "      bFunctionProtocol   %5u\n"
 77                "      iFunction           %5u\n",
 78             assoc_desc->bLength,
 79             assoc_desc->bDescriptorType,
 80             assoc_desc->bFirstInterface,
 81             assoc_desc->bInterfaceCount,
 82             assoc_desc->bFunctionClass,
 83             assoc_desc->bFunctionSubClass,
 84             assoc_desc->bFunctionProtocol,
 85             assoc_desc->iFunction);    
 86 
 87             for (j = 0; j < intf->num_altsetting; j++)
 88             {
 89                 interface = &intf->altsetting[j].desc; //第j個設置的描述符  接口描述符
 90                 printk("    Interface Descriptor altsetting %d:\n"
 91                        "      bLength             %5u\n"
 92                        "      bDescriptorType     %5u\n"
 93                        "      bInterfaceNumber    %5u\n"
 94                        "      bAlternateSetting   %5u\n"
 95                        "      bNumEndpoints       %5u\n"
 96                        "      bInterfaceClass     %5u\n"
 97                        "      bInterfaceSubClass  %5u\n"
 98                        "      bInterfaceProtocol  %5u\n"
 99                        "      iInterface          %5u\n",
100                        j, 
101                        interface->bLength, interface->bDescriptorType, interface->bInterfaceNumber,
102                        interface->bAlternateSetting, interface->bNumEndpoints, interface->bInterfaceClass,
103                        interface->bInterfaceSubClass, interface->bInterfaceProtocol,
104                        interface->iInterface);
105                 /* 打印端點描述符 */
106                 for (m = 0; m < interface->bNumEndpoints; m++)
107                 {
108                     endpoint = &intf->altsetting[j].endpoint[m].desc;
109                     dump_endpoint(endpoint);
110                 }
111                 
112             }
113 　　　　　　　/*自定義描述符*/ 114             buffer = intf->cur_altsetting->extra;
115             buflen = intf->cur_altsetting->extralen;
116             printk("extra buffer of interface %d:\n", cnt-1);
117             k = 0;
118             desc_cnt = 0;
119             while (k < buflen)
120             {
121                 desc_len = buffer[k];
122                 printk("extra desc %d: ", desc_cnt);
123                 for (l = 0; l < desc_len; l++, k++)
124                 {
125                     printk("%02x ", buffer[k]);
126                 }
127                 desc_cnt++;
128                 printk("\n");
129             }
130 　　　　　　　　//模擬lsusb打印內核usb攝像頭信息
131             interface = &intf->cur_altsetting->desc;
132             if ((buffer[1] == USB_DT_CS_INTERFACE) && (interface->bInterfaceSubClass == 1))
133             {
134                 parse_videocontrol_interface(intf, buffer, buflen);
135             }
136             if ((buffer[1] == USB_DT_CS_INTERFACE) && (interface->bInterfaceSubClass == 2))
137             {
138                 parse_videostreaming_interface(intf, buffer, buflen);
139             }
140         
141     }
142     
143     
144     return 0;
145 }

分析：

1. VideoControl Interface的自定義描述符:

[318044.582155] extra buffer of interface 0:
[318044.582156] extra desc 0: 0d 24 01 00 01 4d 00 80 c3 c9 01 01 01 
[318044.582161] extra desc 1: 12 24 02 01 01 02 00 00 00 00 00 00 00 00 03 0e 00 00 
[318044.582166] extra desc 2: 09 24 03 02 01 01 00 04 00 
[318044.582170] extra desc 3: 0b 24 05 03 01 00 00 02 7f 14 00 
[318044.582174] extra desc 4: 1a 24 06 04 ad cc b1 c2 f6 ab b8 48 8e 37 32 d4 f3 a3 fe ec 08 01 03 01 3f 00 

解析：

extra buffer of interface 0:
extra desc 0: 0d 24   01  00 01 4d 00 80 c3 c9 01 01 01
                       VC_HEADER
extra desc 1: 12 24   02                 01 01 02 00 00 00 00 00 00 00 00 03 0e 00 00
                    VC_INPUT_TERMINAL  ID
extra desc 2: 09 24   03                 02 01 01          00             04         00
                      VC_OUTPUT_TERMINAL ID wTerminalType  bAssocTerminal bSourceID
extra desc 3: 0b 24   05                 03 01         00 00           02           7f 14      00   
                     VC_PROCESSING_UNIT ID bSourceID  wMaxMultiplier  bControlSize bmControls         --->UVC 1.5 Class specification 69頁

bControlSize =2表示，後面2個字節，支持哪些功能，該位設爲1表示爲支持此功能；

extra desc 4: 1a 24   06                 04 ad cc b1 c2 f6 ab b8 48 8e 37 32 d4 f3 a3 fe ec 08            01        03         01 3f 00
                      VC_EXTENSION_UNIT  ID GUID                                            bNumControls  bNrInPins baSourceID

從而可知數據流向：IT(01)  ===>  PU(03)  ===>  EU(04)  ===>  OT(02)

1）第1字節爲長度；

2）第2個字節表示爲自定義的；

3）第3個字節爲VC定義的子類：Video Class-Specific VC Interface Descriptor Subtypes 172頁
　　VC_DESCRIPTOR_UNDEFINED 0x00
　　VC_HEADER 0x01
　　VC_INPUT_TERMINAL 0x02
　　VC_OUTPUT_TERMINAL 0x03
　　VC_SELECTOR_UNIT 0x04
　　VC_PROCESSING_UNIT 0x05
　　VC_EXTENSION_UNIT 0x06
　　VC_ENCODING_UNIT 0x07

4）第4個字節爲bSourceID，來源

5）後面字節要根據手冊分析；

2. VideoStreaming Interface的自定義描述符:

[318044.582312] extra buffer of interface 1:
[318044.582313] extra desc 0: 0e 24 01 01 df 00 81 00 02 02 01 01 01 00 
[318044.582317] extra desc 1: 1b 24 04 01 05 59 55 59 32 00 00 10 00 80 00 00 aa 00 38 9b 71 10 01 00 00 00 00 
[318044.582325] extra desc 2: 1e 24 05 01 00 80 02 e0 01 00 00 ca 08 00 00 ca 08 00 60 09 00 15 16 05 00 01 15 16 05 00 
[318044.582333] extra desc 3: 1e 24 05 02 00 60 01 20 01 00 80 e6 02 00 80 e6 02 00 18 03 00 15 16 05 00 01 15 16 05 00 
[318044.582342] extra desc 4: 1e 24 05 03 00 40 01 f0 00 00 80 32 02 00 80 32 02 00 58 02 00 15 16 05 00 01 15 16 05 00 
[318044.582350] extra desc 5: 1e 24 05 04 00 b0 00 90 00 00 a0 b9 00 00 a0 b9 00 00 c6 00 00 15 16 05 00 01 15 16 05 00 
[318044.582358] extra desc 6: 1e 24 05 05 00 a0 00 78 00 00 a0 8c 00 00 a0 8c 00 00 96 00 00 15 16 05 00 01 15 16 05 00 
[318044.582367] extra desc 7: 1a 24 03 00 05 80 02 e0 01 60 01 20 01 40 01 f0 00 b0 00 90 00 a0 00 78 00 00 
[318044.582374] extra desc 8: 06 24 0d 01 01 04 

 分析：

 

第3個字節：數據來源

　　VS_INPUT_HEADER 0x01
　　VS_STILL_IMAGE_FRAME 0x03        // 表示支持靜態圖片，拍照功能
　　VS_FORMAT_UNCOMPRESSED 0x04  // 表示格式
　　VS_FRAME_UNCOMPRESSED 0x05  frame //表示一種格式下可支持多種分辨率 　　VS_COLORFORMAT 0x0D