学习目标：参考lsusb源码，打印USB摄像头的设备描述符、配置描述符、接口联合描述符、端点描述符；
一、lsusb命令和源码
使用命令lsusb可以看看设备的id，并执行 # lsusb -v -d 0x1b3b:2977 命令查看usb摄像头的描述符。
二、源码
打印以下描述符：
程序主要正在probe执行printk函数进行打印：
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 /* 打印设备描述符 */ 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个配置 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_des