第三阶段应用层——2.4 视频监控—从0写USB摄像头驱动（1）-描述符的分析与打印
2024-06-02 19:49:54
视频监控—从0写USB摄像头驱动（1）-描述符的分析与打印
- 硬件平台：韦东山嵌入式Linxu开发板（S3C2440.v3）
- 软件平台：运行于VMware Workstation 12 Player下UbuntuLTS16.04_x64 系统
- 参考资料：USB_Video_Example 1.5、UVC 1.5 Class specification
- 开发环境：Linux-4.13.0-41内核（虚拟机）、arm-linux-gcc-4.3.2工具链
- 源码仓库：https://gitee.com/d_1254436976/Embedded-Linux-Phase-3
目录
- 视频监控—从0写USB摄像头驱动（1）-描述符的分析与打印
- 一、描述符
- 1、什么是描述符
- 2、USB设备的描述符
- 3、UVC-Video类中的描述符
- 二、打印USB摄像头的描述符
- 1、代码的编写
- 2、Makefile编写
- 3、运行与分析
- 3.1 运行
- 3.2 分析
一、描述符
1、什么是描述符
关于这个概念也没有一个准确的定义，可以理解为与 “被描述物” 相关联的一组数据或数据结构，用来记录被描述物的 “属性”。
具体体现如下（举例说明，并非所有）：
- 数字，如Linux中的文件描述符，表示一个打开的文件
- 结构体，这个在C语言中比较常见，结构体中存储的成员变量的数据就是该设备的具体描述
- 类，这个在C++与Java中比较常见，其成员变量的数据就是该设备的具体描述
2、USB设备的描述符
对于usb描述符，用来描述该usb设备的属性，如：设备类型、设备型号、配置、容量大小等等
对于一个usb设备，其必有如下固定描述符：
- USB设备描述符（usb_device_descriptor）：描述该USB设备的一般信息，如厂家信息、协议信息、usb版本等，一个USB设备只有一个设备描述符
访问方式：USB设备结构体usb_device的descriptor成员变量中
struct usb_device_descriptor {__u8 bLength; //本描述符的size__u8 bDescriptorType; //描述符的类型，这里是设备描述符DEVICE__u16 bcdUSB; //指明usb的版本，比如usb2.0__u8 bDeviceClass; //类__u8 bDeviceSubClass; //子类__u8 bDeviceProtocol; //指定协议__u8 bMaxPacketSize0; //端点0对应的最大包大小__u16 idVendor; //厂家ID__u16 idProduct; //产品ID__u16 bcdDevice; //设备的发布号__u8 iManufacturer; //字符串描述符中厂家ID的索引__u8 iProduct; //字符串描述符中产品ID的索引__u8 iSerialNumber; //字符串描述符中设备序列号的索引__u8 bNumConfigurations; //配置描述符的个数,表示有多少个配置描述符
} __attribute__ ((packed));
- USB配置描述符（usb_config_descriptor）：描述有关特定设备配置的信息，主机获取到设备描述符之后，就会获取配置描述符，一个设置描述符可以有一个或多个配置描述符。
访问方式：USB设备结构体usb_device->config[ ]（所有配置）.desc
usb_device->actconfig（当前激活的配置）->desc
struct usb_config_descriptor { __u8 bLength; //描述符的长度__u8 bDescriptorType; //描述符类型的编号__le16 wTotalLength; //配置 所返回的所有数据的大小__u8 bNumInterfaces; //配置 所支持的接口个数, 表示有多少个接口描述符__u8 bConfigurationValue; //Set_Configuration命令需要的参数值__u8 iConfiguration; //描述该配置的字符串的索引值__u8 bmAttributes; //供电模式的选择__u8 bMaxPower; //设备从总线提取的最大电流} __attribute__ ((packed));
- USB接口描述符（usb_interface_descriptor）：描述配置中的特定接口，一个配置提供一个或多个接口（对于一个声卡设备，拥有音频输入接口与输出接口）
访问方式：usb_interface->cur_altsetting（当前激活的接口）->desc
usb_interface->altsetting[ ]（所有的接口）.desc
struct usb_interface_descriptor { __u8 bLength; //描述符的长度__u8 bDescriptorType; //描述符类型的编号__u8 bInterfaceNumber; //接口的编号__u8 bAlternateSetting; //备用的接口描述符编号,提供不同质量的服务参数.__u8 bNumEndpoints; //要使用的端点个数(不包括端点0), 表示有多少个端点描述符,比如鼠标就只有一个端点__u8 bInterfaceClass; //接口类型,与驱动的id_table__u8 bInterfaceSubClass; //接口子类型__u8 bInterfaceProtocol; //接口所遵循的协议__u8 iInterface; //描述该接口的字符串索引值
} __attribute__ ((packed)
- USB端点描述符（usb_endpoint_descriptor）：描述该接口中每个端点的带宽要求所需的信息。
访问方式：usb_interface->cur_altsetting（当前激活的接口）->endpoint[] （所有端点）.desc
struct usb_endpoint_descriptor {__u8 bLength; //描述符的长度__u8 bDescriptorType; //描述符类型的编号__u8 bEndpointAddress; //端点编号,比如端点1,就是1__u8 bmAttributes; //端点的属性, 比如中断传输类型,输入类型__le16 wMaxPacketSize; //一个端点的最大包大小,__u8 bInterval; //间隔时间,用在中断传输上,比如间隔时间查询鼠标的数据/* NOTE: these two are _only_ in audio endpoints. *//* use USB_DT_ENDPOINT*_SIZE in bLength, not sizeof. */__u8 bRefresh;__u8 bSynchAddress;
} __attribute__ ((packed));
四者的关系如下：
一个USB设备只有一个USB设备描述符
一个设置描述符可以有一个或多个配置描述符
一个配置描述符可以有一个或多个接口描述符
一个接口描述符可以有一个或多个端点描述符
3、UVC-Video类中的描述符
参考手册，得到如下图：其中白色底为固定的描述符，灰色底为此设备拓展的描述符。
二、打印USB摄像头的描述符
使用到的USB摄像头为百问网的usb-cmos二合一摄像头，参考libusb-1.0.16-rc10源码
1、代码的编写
/******************************************************************************** Copyleft (c) 2021 Kcode** @file myuvc.c* @brief 打印usb的设备、配置、IAD、接口、自定义、端点描述符并解析自定义描述符* @author K* @version 0.0.1* @date 2021-07-21* @license MulanPSL-1.0** 文件修改历史：* <时间> | <版本> | <作者> | <描述>* 2021-07-21 | v0.0.1 | Kcode | 打印并解析描述符* -----------------------------------------------------------------------------******************************************************************************/#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/videodev2.h>
#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <asm/atomic.h>
#include <asm/unaligned.h>#include <media/v4l2-common.h>/*!* 所支持的usb设备类*/
static struct usb_device_id myuvc_ids[] = {/* Generic USB Video Class */{ USB_INTERFACE_INFO(USB_CLASS_VIDEO, 1, 0) }, /**< VideoControl interface */{ USB_INTERFACE_INFO(USB_CLASS_VIDEO, 2, 0) }, /**< VideoStreaming interface */{}
};static const char *get_guid(const unsigned char *buf)
{static char guid[39];/* NOTE: see RFC 4122 for more information about GUID/UUID* structure. The first fields fields are historically big* endian numbers, dating from Apollo mc68000 workstations.*/sprintf(guid, "{%02x%02x%02x%02x""-%02x%02x""-%02x%02x""-%02x%02x""-%02x%02x%02x%02x%02x%02x}",buf[0], buf[1], buf[2], buf[3],buf[4], buf[5],buf[6], buf[7],buf[8], buf[9],buf[10], buf[11], buf[12], buf[13], buf[14], buf[15]);return guid;
}/*!* 解析VideoControl Interface接口的自定义描述符*/
static void parse_videocontrol_interface(struct usb_interface *intf,unsigned char *buf, int buflen)
{static const char * const ctrlnames[] = {"Brightness", "Contrast", "Hue", "Saturation", "Sharpness", "Gamma","White Balance Temperature", "White Balance Component", "Backlight Compensation","Gain", "Power Line Frequency", "Hue, Auto", "White Balance Temperature, Auto","White Balance Component, Auto", "Digital Multiplier", "Digital Multiplier Limit","Analog Video Standard", "Analog Video Lock Status"};static const char * const camctrlnames[] = {"Scanning Mode", "Auto-Exposure Mode", "Auto-Exposure Priority","Exposure Time (Absolute)", "Exposure Time (Relative)", "Focus (Absolute)","Focus (Relative)", "Iris (Absolute)", "Iris (Relative)", "Zoom (Absolute)","Zoom (Relative)", "PanTilt (Absolute)", "PanTilt (Relative)","Roll (Absolute)", "Roll (Relative)", "Reserved", "Reserved", "Focus, Auto","Privacy"};static const char * const stdnames[] = {"None", "NTSC - 525/60", "PAL - 625/50", "SECAM - 625/50","NTSC - 625/50", "PAL - 525/60" };unsigned int i, ctrls, stds, n, p, termt, freq;/*!* 打印所有的在VideoControl Interface接口下的自定义描述符*/while (buflen > 0) {if (buf[1] != USB_DT_CS_INTERFACE)printk(" Warning: Invalid descriptor\n");else if (buf[0] < 3)printk(" Warning: Descriptor too short\n");printk(" VideoControl Interface Descriptor:\n"" bLength %5u\n"" bDescriptorType %5u\n"" bDescriptorSubtype %5u ",buf[0], buf[1], buf[2]);switch (buf[2]) {case 0x01: /* HEADER */printk("(HEADER)\n");n = buf[11];if (buf[0] < 12+n)printk(" Warning: Descriptor too short\n");freq = buf[7] | (buf[8] << 8) | (buf[9] << 16) | (buf[10] << 24);printk(" bcdUVC %2x.%02x\n"" wTotalLength %5u\n"" dwClockFrequency %5u.%06uMHz\n"" bInCollection %5u\n",buf[4], buf[3], buf[5] | (buf[6] << 8), freq / 1000000,freq % 1000000, n);for (i = 0; i < n; i++)printk(" baInterfaceNr(%2u) %5u\n", i, buf[12+i]);break;case 0x02: /* INPUT_TERMINAL */printk("(INPUT_TERMINAL)\n");termt = buf[4] | (buf[5] << 8);n = termt == 0x0201 ? 7 : 0;if (buf[0] < 8 + n)printk(" Warning: Descriptor too short\n");printk(" bTerminalID %5u\n"" wTerminalType 0x%04x\n"" bAssocTerminal %5u\n",buf[3], termt, buf[6]);printk(" iTerminal %5u\n",buf[7]);if (termt == 0x0201) {n += buf[14];printk(" wObjectiveFocalLengthMin %5u\n"" wObjectiveFocalLengthMax %5u\n"" wOcularFocalLength %5u\n"" bControlSize %5u\n",buf[8] | (buf[9] << 8), buf[10] | (buf[11] << 8),buf[12] | (buf[13] << 8), buf[14]);ctrls = 0;for (i = 0; i < 3 && i < buf[14]; i++)ctrls = (ctrls << 8) | buf[8+n-i-1];printk(" bmControls 0x%08x\n", ctrls);for (i = 0; i < 19; i++)if ((ctrls >> i) & 1)printk(" %s\n", camctrlnames[i]);}break;case 0x03: /* OUTPUT_TERMINAL */printk("(OUTPUT_TERMINAL)\n");termt = buf[4] | (buf[5] << 8);if (buf[0] < 9)printk(" Warning: Descriptor too short\n");printk(" bTerminalID %5u\n"" wTerminalType 0x%04x\n"" bAssocTerminal %5u\n"" bSourceID %5u\n"" iTerminal %5u\n",buf[3], termt, buf[6], buf[7], buf[8]);break;case 0x04: /* SELECTOR_UNIT */printk("(SELECTOR_UNIT)\n");p = buf[4];if (buf[0] < 6+p)printk(" Warning: Descriptor too short\n");printk(" bUnitID %5u\n"" bNrInPins %5u\n",buf[3], p);for (i = 0; i < p; i++)printk(" baSource(%2u) %5u\n", i, buf[5+i]);printk(" iSelector %5u\n",buf[5+p]);break;case 0x05: /* PROCESSING_UNIT */printk("(PROCESSING_UNIT)\n");n = buf[7];if (buf[0] < 10+n)printk(" Warning: Descriptor too short\n");printk(" bUnitID %5u\n"" bSourceID %5u\n"" wMaxMultiplier %5u\n"" bControlSize %5u\n",buf[3], buf[4], buf[5] | (buf[6] << 8), n);ctrls = 0;for (i = 0; i < 3 && i < n; i++)ctrls = (ctrls << 8) | buf[8+n-i-1];printk(" bmControls 0x%08x\n", ctrls);for (i = 0; i < 18; i++)if ((ctrls >> i) & 1)printk(" %s\n", ctrlnames[i]);stds = buf[9+n];printk(" iProcessing %5u\n"" bmVideoStandards 0x%2x\n", buf[8+n], stds);for (i = 0; i < 6; i++)if ((stds >> i) & 1)printk(" %s\n", stdnames[i]);break;case 0x06: /* EXTENSION_UNIT */printk("(EXTENSION_UNIT)\n");p = buf[21];n = buf[22+p];if (buf[0] < 24+p+n)printk(" Warning: Descriptor too short\n");printk(" bUnitID %5u\n"" guidExtensionCode %s\n"" bNumControl %5u\n"" bNrPins %5u\n",buf[3], get_guid(&buf[4]), buf[20], buf[21]);for (i = 0; i < p; i++)printk(" baSourceID(%2u) %5u\n", i, buf[22+i]);printk(" bControlSize %5u\n", buf[22+p]);for (i = 0; i < n; i++)printk(" bmControls(%2u) 0x%02x\n", i, buf[23+p+i]);printk(" iExtension %5u\n",buf[23+p+n]);break;default:printk("(unknown)\n"" Invalid desc subtype:");break;}buflen -= buf[0];buf += buf[0];}
}/*!* 打印端点描述符*/
static void dump_endpoint(const struct usb_endpoint_descriptor *endpoint)
{static const char * const typeattr[] = {"Control","Isochronous","Bulk","Interrupt"};static const char * const syncattr[] = {"None","Asynchronous","Adaptive","Synchronous"};static const char * const usage[] = {"Data","Feedback","Implicit feedback Data","(reserved)"};static const char * const hb[] = { "1x", "2x", "3x", "(?\?)" };unsigned wmax = le16_to_cpu(endpoint->wMaxPacketSize);printk(" Endpoint Descriptor:\n"" bLength %5u\n"" bDescriptorType %5u\n"" bEndpointAddress 0x%02x EP %u %s\n"" bmAttributes %5u\n"" Transfer Type %s\n"" Synch Type %s\n"" Usage Type %s\n"" wMaxPacketSize 0x%04x %s %d bytes\n"" bInterval %5u\n",endpoint->bLength,endpoint->bDescriptorType,endpoint->bEndpointAddress,endpoint->bEndpointAddress & 0x0f,(endpoint->bEndpointAddress & 0x80) ? "IN" : "OUT",endpoint->bmAttributes,typeattr[endpoint->bmAttributes & 3],syncattr[(endpoint->bmAttributes >> 2) & 3],usage[(endpoint->bmAttributes >> 4) & 3],wmax, hb[(wmax >> 11) & 3], wmax & 0x7ff,endpoint->bInterval);/* only for audio endpoints */if (endpoint->bLength == 9)printk(" bRefresh %5u\n"" bSynchAddress %5u\n",endpoint->bRefresh, endpoint->bSynchAddress);}/*!* 解析VideoStreaming Interface接口的自定义描述符*/
static void parse_videostreaming_interface(struct usb_interface *intf, unsigned char *buf, int buflen)
{static const char * const colorPrims[] = { "Unspecified", "BT.709,sRGB","BT.470-2 (M)", "BT.470-2 (B,G)", "SMPTE 170M", "SMPTE 240M" };static const char * const transferChars[] = { "Unspecified", "BT.709","BT.470-2 (M)", "BT.470-2 (B,G)", "SMPTE 170M", "SMPTE 240M","Linear", "sRGB"};static const char * const matrixCoeffs[] = { "Unspecified", "BT.709","FCC", "BT.470-2 (B,G)", "SMPTE 170M (BT.601)", "SMPTE 240M" };unsigned int i, m, n, p, flags, len;/*!* 打印所有的在VideoSteaming Interface接口下的自定义描述符*/while (buflen > 0) {if (buf[1] != USB_DT_CS_INTERFACE)printk(" Warning: Invalid descriptor\n");else if (buf[0] < 3)printk(" Warning: Descriptor too short\n");printk(" VideoStreaming Interface Descriptor:\n"" bLength %5u\n"" bDescriptorType %5u\n"" bDescriptorSubtype %5u ",buf[0], buf[1], buf[2]);switch (buf[2]) {case 0x01: /* INPUT_HEADER */printk("(INPUT_HEADER)\n");p = buf[3];n = buf[12];if (buf[0] < 13+p*n)printk(" Warning: Descriptor too short\n");printk(" bNumFormats %5u\n"" wTotalLength %5u\n"" bEndPointAddress %5u\n"" bmInfo %5u\n"" bTerminalLink %5u\n"" bStillCaptureMethod %5u\n"" bTriggerSupport %5u\n"" bTriggerUsage %5u\n"" bControlSize %5u\n",p, buf[4] | (buf[5] << 8), buf[6], buf[7], buf[8],buf[9], buf[10], buf[11], n);for (i = 0; i < p; i++)printk(" bmaControls(%2u) %5u\n",i, buf[13+p*n]);break;case 0x02: /* OUTPUT_HEADER */printk("(OUTPUT_HEADER)\n");p = buf[3];n = buf[8];if (buf[0] < 9+p*n)printk(" Warning: Descriptor too short\n");printk(" bNumFormats %5u\n"" wTotalLength %5u\n"" bEndpointAddress %5u\n"" bTerminalLink %5u\n"" bControlSize %5u\n",p, buf[4] | (buf[5] << 8), buf[6], buf[7], n);for (i = 0; i < p; i++)printk(" bmaControls(%2u) %5u\n",i, buf[9+p*n]);break;case 0x03: /* STILL_IMAGE_FRAME */printk("(STILL_IMAGE_FRAME)\n");n = buf[4];m = buf[5+4*n];if (buf[0] < 6+4*n+m)printk(" Warning: Descriptor too short\n");printk(" bEndpointAddress %5u\n"" bNumImageSizePatterns %3u\n",buf[3], n);for (i = 0; i < n; i++)printk(" wWidth(%2u) %5u\n"" wHeight(%2u) %5u\n",i, buf[5+4*i] | (buf[6+4*i] << 8),i, buf[7+4*i] | (buf[8+4*i] << 8));printk(" bNumCompressionPatterns %3u\n", n);for (i = 0; i < m; i++)printk(" bCompression(%2u) %5u\n",i, buf[6+4*n+i]);break;case 0x04: /* FORMAT_UNCOMPRESSED */case 0x10: /* FORMAT_FRAME_BASED */if (buf[2] == 0x04) {printk("(FORMAT_UNCOMPRESSED)\n");len = 27;} else {printk("(FORMAT_FRAME_BASED)\n");len = 28;}if (buf[0] < len)printk(" Warning: Descriptor too short\n");flags = buf[25];printk(" bFormatIndex %5u\n"" bNumFrameDescriptors %5u\n"" guidFormat %s\n"" bBitsPerPixel %5u\n"" bDefaultFrameIndex %5u\n"" bAspectRatioX %5u\n"" bAspectRatioY %5u\n"" bmInterlaceFlags 0x%02x\n",buf[3], buf[4], get_guid(&buf[5]), buf[21], buf[22],buf[23], buf[24], flags);printk(" Interlaced stream or variable: %s\n",(flags & (1 << 0)) ? "Yes" : "No");printk(" Fields per frame: %u fields\n",(flags & (1 << 1)) ? 1 : 2);printk(" Field 1 first: %s\n",(flags & (1 << 2)) ? "Yes" : "No");printk(" Field pattern: ");switch ((flags >> 4) & 0x03) {case 0:printk("Field 1 only\n");break;case 1:printk("Field 2 only\n");break;case 2:printk("Regular pattern of fields 1 and 2\n");break;case 3:printk("Random pattern of fields 1 and 2\n");break;}printk(" bCopyProtect %5u\n", buf[26]);if (buf[2] == 0x10)printk(" bVariableSize %5u\n", buf[27]);break;case 0x05: /* FRAME UNCOMPRESSED */case 0x07: /* FRAME_MJPEG */case 0x11: /* FRAME_FRAME_BASED */if (buf[2] == 0x05) {printk("(FRAME_UNCOMPRESSED)\n");n = 25;} else if (buf[2] == 0x07) {printk("(FRAME_MJPEG)\n");n = 25;} else {printk("(FRAME_FRAME_BASED)\n");n = 21;}len = (buf[n] != 0) ? (26+buf[n]*4) : 38;if (buf[0] < len)printk(" Warning: Descriptor too short\n");flags = buf[4];printk(" bFrameIndex %5u\n"" bmCapabilities 0x%02x\n",buf[3], flags);printk(" Still image %ssupported\n",(flags & (1 << 0)) ? "" : "un");if (flags & (1 << 1))printk(" Fixed frame-rate\n");printk(" wWidth %5u\n"" wHeight %5u\n"" dwMinBitRate %9u\n"" dwMaxBitRate %9u\n",buf[5] | (buf[6] << 8), buf[7] | (buf[8] << 8),buf[9] | (buf[10] << 8) | (buf[11] << 16) | (buf[12] << 24),buf[13] | (buf[14] << 8) | (buf[15] << 16) | (buf[16] << 24));if (buf[2] == 0x11)printk(" dwDefaultFrameInterval %9u\n"" bFrameIntervalType %5u\n"" dwBytesPerLine %9u\n",buf[17] | (buf[18] << 8) | (buf[19] << 16) | (buf[20] << 24),buf[21],buf[22] | (buf[23] << 8) | (buf[24] << 16) | (buf[25] << 24));elseprintk(" dwMaxVideoFrameBufferSize %9u\n"" dwDefaultFrameInterval %9u\n"" bFrameIntervalType %5u\n",buf[17] | (buf[18] << 8) | (buf[19] << 16) | (buf[20] << 24),buf[21] | (buf[22] << 8) | (buf[23] << 16) | (buf[24] << 24),buf[25]);if (buf[n] == 0)printk(" dwMinFrameInterval %9u\n"" dwMaxFrameInterval %9u\n"" dwFrameIntervalStep %9u\n",buf[26] | (buf[27] << 8) | (buf[28] << 16) | (buf[29] << 24),buf[30] | (buf[31] << 8) | (buf[32] << 16) | (buf[33] << 24),buf[34] | (buf[35] << 8) | (buf[36] << 16) | (buf[37] << 24));elsefor (i = 0; i < buf[n]; i++)printk(" dwFrameInterval(%2u) %9u\n",i, buf[26+4*i] | (buf[27+4*i] << 8) |(buf[28+4*i] << 16) | (buf[29+4*i] << 24));break;case 0x06: /* FORMAT_MJPEG */printk("(FORMAT_MJPEG)\n");if (buf[0] < 11)printk(" Warning: Descriptor too short\n");flags = buf[5];printk(" bFormatIndex %5u\n"" bNumFrameDescriptors %5u\n"" bFlags %5u\n",buf[3], buf[4], flags);printk(" Fixed-size samples: %s\n",(flags & (1 << 0)) ? "Yes" : "No");flags = buf[9];printk(" bDefaultFrameIndex %5u\n"" bAspectRatioX %5u\n"" bAspectRatioY %5u\n"" bmInterlaceFlags 0x%02x\n",buf[6], buf[7], buf[8], flags);printk(" Interlaced stream or variable: %s\n",(flags & (1 << 0)) ? "Yes" : "No");printk(" Fields per frame: %u fields\n",(flags & (1 << 1)) ? 2 : 1);printk(" Field 1 first: %s\n",(flags & (1 << 2)) ? "Yes" : "No");printk(" Field pattern: ");switch ((flags >> 4) & 0x03) {case 0:printk("Field 1 only\n");break;case 1:printk("Field 2 only\n");break;case 2:printk("Regular pattern of fields 1 and 2\n");break;case 3:printk("Random pattern of fields 1 and 2\n");break;}printk(" bCopyProtect %5u\n", buf[10]);break;case 0x0a: /* FORMAT_MPEG2TS */printk("(FORMAT_MPEG2TS)\n");len = buf[0] < 23 ? 7 : 23;if (buf[0] < len)printk(" Warning: Descriptor too short\n");printk(" bFormatIndex %5u\n"" bDataOffset %5u\n"" bPacketLength %5u\n"" bStrideLength %5u\n",buf[3], buf[4], buf[5], buf[6]);if (len > 7)printk(" guidStrideFormat %s\n",get_guid(&buf[7]));break;case 0x0d: /* COLORFORMAT */printk("(COLORFORMAT)\n");if (buf[0] < 6)printk(" Warning: Descriptor too short\n");printk(" bColorPrimaries %5u (%s)\n",buf[3], (buf[3] <= 5) ? colorPrims[buf[3]] : "Unknown");printk(" bTransferCharacteristics %5u (%s)\n",buf[4], (buf[4] <= 7) ? transferChars[buf[4]] : "Unknown");printk(" bMatrixCoefficients %5u (%s)\n",buf[5], (buf[5] <= 5) ? matrixCoeffs[buf[5]] : "Unknown");break;default:printk(" Invalid desc subtype:");break;}buflen -= buf[0];buf += buf[0];}}static int myuvc_probe(struct usb_interface *intf,const struct usb_device_id *id)
{ unsigned char *buffer;int i, j, k, l, m;int buflen;int desc_len;int desc_cnt;static int cnt = 0;struct usb_device *dev = interface_to_usbdev(intf);struct usb_device_descriptor *descriptor = &dev->descriptor;struct usb_host_config *hostconfig;struct usb_config_descriptor *config;struct usb_interface_assoc_descriptor *assoc_desc;struct usb_interface_descriptor *interface;struct usb_endpoint_descriptor *endpoint;printk("myuvc_probe : cnt = %d\n", cnt++);/*!* 打印设备描述符*/printk("Device Descriptor:\n"" bLength %5u\n"" bDescriptorType %5u\n"" bcdUSB %2x.%02x\n"" bDeviceClass %5u \n"" bDeviceSubClass %5u \n"" bDeviceProtocol %5u \n"" bMaxPacketSize0 %5u\n"" idVendor 0x%04x \n"" idProduct 0x%04x \n"" bcdDevice %2x.%02x\n"" iManufacturer %5u\n"" iProduct %5u\n"" iSerial %5u\n"" bNumConfigurations %5u\n",descriptor->bLength, descriptor->bDescriptorType,descriptor->bcdUSB >> 8, descriptor->bcdUSB & 0xff,descriptor->bDeviceClass, descriptor->bDeviceSubClass,descriptor->bDeviceProtocol, descriptor->bMaxPacketSize0,descriptor->idVendor, descriptor->idProduct,descriptor->bcdDevice >> 8, descriptor->bcdDevice & 0xff,descriptor->iManufacturer, descriptor->iProduct, descriptor->iSerialNumber, descriptor->bNumConfigurations);/*!* 打印配置描述符*/for (i = 0; i < descriptor->bNumConfigurations; i++) {hostconfig = &dev->config[i];config = &hostconfig->desc;printk(" Configuration Descriptor %d:\n"" bLength %5u\n"" bDescriptorType %5u\n"" wTotalLength %5u\n"" bNumInterfaces %5u\n"" bConfigurationValue %5u\n"" iConfiguration %5u\n"" bmAttributes 0x%02x\n",i, config->bLength, config->bDescriptorType,le16_to_cpu(config->wTotalLength),config->bNumInterfaces, config->bConfigurationValue,config->iConfiguration,config->bmAttributes);/*!* 打印IAD描述符*/assoc_desc = hostconfig->intf_assoc[0];printk(" Interface Association:\n"" bLength %5u\n"" bDescriptorType %5u\n"" bFirstInterface %5u\n"" bInterfaceCount %5u\n"" bFunctionClass %5u\n"" bFunctionSubClass %5u\n"" bFunctionProtocol %5u\n"" iFunction %5u\n",assoc_desc->bLength,assoc_desc->bDescriptorType,assoc_desc->bFirstInterface,assoc_desc->bInterfaceCount,assoc_desc->bFunctionClass,assoc_desc->bFunctionSubClass,assoc_desc->bFunctionProtocol,assoc_desc->iFunction);/*!* 可能有多个接口，根据intf->num_altsetting数* 打印每一个接口的描述符*/for (j = 0; j < intf->num_altsetting; j++) {interface = &intf->altsetting[j].desc;printk(" Interface Descriptor altsetting %d:\n"" bLength %5u\n"" bDescriptorType %5u\n"" bInterfaceNumber %5u\n"" bAlternateSetting %5u\n"" bNumEndpoints %5u\n"" bInterfaceClass %5u\n"" bInterfaceSubClass %5u\n"" bInterfaceProtocol %5u\n"" iInterface %5u\n",j, interface->bLength, interface->bDescriptorType, interface->bInterfaceNumber, interface->bAlternateSetting, interface->bNumEndpoints, interface->bInterfaceClass,interface->bInterfaceSubClass, interface->bInterfaceProtocol,interface->iInterface);/*!* 打印端点描述符*/for (m = 0; m < interface->bNumEndpoints; m++) {endpoint = &intf->altsetting[j].endpoint[m].desc;dump_endpoint(endpoint);}}/*!* 打印设备本身自定义的描述符，二进制形式*/buffer = intf->cur_altsetting->extra;buflen = intf->cur_altsetting->extralen;printk("extra buffer of interface %d:\n", cnt-1);k = 0;desc_cnt = 0;while (k < buflen){desc_len = buffer[k];printk("extra desc %d: ", desc_cnt);for (l = 0; l < desc_len; l++, k++) {printk("%02x ", buffer[k]);}desc_cnt++;printk("\n");}interface = &intf->cur_altsetting->desc; /**< 获取接口描述符 *//*!* 解析VideoControl Interface接口下的自定义描述符*/if ((buffer[1] == USB_DT_CS_INTERFACE) && (interface->bInterfaceSubClass == 1))parse_videocontrol_interface(intf, buffer, buflen);/*!* 解析VideoStreaming Interface接口下的自定义描述符*/if ((buffer[1] == USB_DT_CS_INTERFACE) && (interface->bInterfaceSubClass == 2))parse_videostreaming_interface(intf, buffer, buflen); }return 0;
}static void myuvc_disconnect(struct usb_interface *intf)
{static int cnt = 0;printk("myuvc_disconnect : cnt = %d\n", cnt++);
}struct usb_driver myuvc_driver = {.name = "myuvcvideo",.probe = myuvc_probe,.disconnect = myuvc_disconnect,.id_table = myuvc_ids,
};static int myuvc_init(void)
{int result;result = usb_register(&myuvc_driver);if (result == 0)printk("USB register error!\n");return result;
}static void myuvc_cleanup(void)
{usb_deregister(&myuvc_driver);
}module_init(myuvc_init);
module_exit(myuvc_cleanup);
MODULE_LICENSE("GPL")
2、Makefile编写
KERN_DIR = /usr/src/linux-headers-4.13.0-41-genericall:make -C $(KERN_DIR) M=`pwd` modules clean:make -C $(KERN_DIR) M=`pwd` modules cleanrm -rf modules.orderobj-m += myuvc.o
3、运行与分析
3.1 运行
执行make，生成驱动文件并插入USB摄像头之后，卸载原先虚拟机的摄像头驱动sudo rmmod uvcvideo，装载新驱动sudo insmod myuvc.ko，后执行dmesg > dmesg.txt把信息输出到txt中。
3.2 分析
整理后的dmesg.txt信息如下：
由于代码中支持列表中填写了VideoControl Interface和VideoStreaming Interface，且摄像头都支持，所以会打印两次设备描述符（两次打印的是同一个设备描述符），实际使用只需要保留第一个
对于使用的摄像头
- 有一个配置： bDeviceProtocol 1
- 该配置下有4个接口：bNumInterfaces 4
- 打印所有接口下的端点信息
- 打印并解析了
VideoControl Interface和VideoStreaming Interface接口下的自定义配置
myuvc_disconnect : cnt = 0myuvc_disconnect : cnt = 1myuvc_probe : cnt = 0Device Descriptor:bLength 18bDescriptorType 1bcdUSB 2.00bDeviceClass 239 bDeviceSubClass 2 bDeviceProtocol 1 bMaxPacketSize0 64idVendor 0x1b3b idProduct 0x2977 bcdDevice 1.0aiManufacturer 0iProduct 0iSerial 0bNumConfigurations 1Configuration Descriptor 0:bLength 9bDescriptorType 2wTotalLength 492bNumInterfaces 4bConfigurationValue 1iConfiguration 0bmAttributes 0x80Interface Association:bLength 8bDescriptorType 11bFirstInterface 0bInterfaceCount 2bFunctionClass 14bFunctionSubClass 3bFunctionProtocol 0iFunction 0Interface Descriptor altsetting 0:bLength 9bDescriptorType 4bInterfaceNumber 0bAlternateSetting 0bNumEndpoints 1bInterfaceClass 14bInterfaceSubClass 1bInterfaceProtocol 0iInterface 0Endpoint Descriptor:bLength 7bDescriptorType 5bEndpointAddress 0x81 EP 1 INbmAttributes 3Transfer Type InterruptSynch Type NoneUsage Type DatawMaxPacketSize 0x0040 1x 64 bytesbInterval 6extra buffer of interface 0:extra desc 0: 0d 24 01 00 01 4d 00 80 8d 5b 00 01 01 extra desc 1: 12 24 02 01 01 02 00 00 01 00 03 00 01 00 03 80 2a 00 extra desc 2: 0b 24 05 03 01 00 00 02 3f 05 00 extra desc 3: 1a 24 06 04 3a ab 91 99 ef b2 c9 48 8f e9 8f e3 63 47 71 d0 08 01 03 01 0f 00 extra desc 4: 09 24 03 02 01 01 00 04 00 VideoControl Interface Descriptor:bLength 13bDescriptorType 36bDescriptorSubtype 1 (HEADER)bcdUVC 1.00wTotalLength 77dwClockFrequency 6.000000MHzbInCollection 1baInterfaceNr( 0) 1VideoControl Interface Descriptor:bLength 18bDescriptorType 36bDescriptorSubtype 2 (INPUT_TERMINAL)bTerminalID 1wTerminalType 0x0201bAssocTerminal 0iTerminal 0wObjectiveFocalLengthMin 1wObjectiveFocalLengthMax 3wOcularFocalLength 1bControlSize 3bmControls 0x00002a80Iris (Absolute)Zoom (Absolute)PanTilt (Absolute)Roll (Absolute)VideoControl Interface Descriptor:bLength 11bDescriptorType 36bDescriptorSubtype 5 (PROCESSING_UNIT)Warning: Descriptor too shortbUnitID 3bSourceID 1wMaxMultiplier 0bControlSize 2bmControls 0x0000053fBrightnessContrastHueSaturationSharpnessGammaBacklight CompensationPower Line FrequencyiProcessing 0bmVideoStandards 0x1aNTSC - 525/60SECAM - 625/50NTSC - 625/50VideoControl Interface Descriptor:bLength 26bDescriptorType 36bDescriptorSubtype 6 (EXTENSION_UNIT)bUnitID 4guidExtensionCode {3aab9199-efb2-c948-8fe9-8fe3634771d0}bNumControl 8bNrPins 1baSourceID( 0) 3bControlSize 1bmControls( 0) 0x0fiExtension 0VideoControl Interface Descriptor:bLength 9bDescriptorType 36bDescriptorSubtype 3 (OUTPUT_TERMINAL)bTerminalID 2wTerminalType 0x0101bAssocTerminal 0bSourceID 4iTerminal 0myuvc_probe : cnt = 1Device Descriptor:bLength 18bDescriptorType 1bcdUSB 2.00bDeviceClass 239 bDeviceSubClass 2 bDeviceProtocol 1 bMaxPacketSize0 64idVendor 0x1b3b idProduct 0x2977 bcdDevice 1.0aiManufacturer 0iProduct 0iSerial 0bNumConfigurations 1Configuration Descriptor 0:bLength 9bDescriptorType 2wTotalLength 492bNumInterfaces 4bConfigurationValue 1iConfiguration 0bmAttributes 0x80Interface Association:bLength 8bDescriptorType 11bFirstInterface 0bInterfaceCount 2bFunctionClass 14bFunctionSubClass 3bFunctionProtocol 0iFunction 0Interface Descriptor altsetting 0:bLength 9bDescriptorType 4bInterfaceNumber 1bAlternateSetting 0bNumEndpoints 0bInterfaceClass 14bInterfaceSubClass 2bInterfaceProtocol 0iInterface 0Interface Descriptor altsetting 1:bLength 9bDescriptorType 4bInterfaceNumber 1bAlternateSetting 1bNumEndpoints 1bInterfaceClass 14bInterfaceSubClass 2bInterfaceProtocol 0iInterface 0Endpoint Descriptor:bLength 7bDescriptorType 5bEndpointAddress 0x82 EP 2 INbmAttributes 5Transfer Type IsochronousSynch Type AsynchronousUsage Type DatawMaxPacketSize 0x0080 1x 128 bytesbInterval 1Interface Descriptor altsetting 2:bLength 9bDescriptorType 4bInterfaceNumber 1bAlternateSetting 2bNumEndpoints 1bInterfaceClass 14bInterfaceSubClass 2bInterfaceProtocol 0iInterface 0Endpoint Descriptor:bLength 7bDescriptorType 5bEndpointAddress 0x82 EP 2 INbmAttributes 5Transfer Type IsochronousSynch Type AsynchronousUsage Type DatawMaxPacketSize 0x0100 1x 256 bytesbInterval 1Interface Descriptor altsetting 3:bLength 9bDescriptorType 4bInterfaceNumber 1bAlternateSetting 3bNumEndpoints 1bInterfaceClass 14bInterfaceSubClass 2bInterfaceProtocol 0iInterface 0Endpoint Descriptor:bLength 7bDescriptorType 5bEndpointAddress 0x82 EP 2 INbmAttributes 5Transfer Type IsochronousSynch Type AsynchronousUsage Type DatawMaxPacketSize 0x0200 1x 512 bytesbInterval 1Interface Descriptor altsetting 4:bLength 9bDescriptorType 4bInterfaceNumber 1bAlternateSetting 4bNumEndpoints 1bInterfaceClass 14bInterfaceSubClass 2bInterfaceProtocol 0iInterface 0Endpoint Descriptor:bLength 7bDescriptorType 5bEndpointAddress 0x82 EP 2 INbmAttributes 5Transfer Type IsochronousSynch Type AsynchronousUsage Type DatawMaxPacketSize 0x0258 1x 600 bytesbInterval 1Interface Descriptor altsetting 5:bLength 9bDescriptorType 4bInterfaceNumber 1bAlternateSetting 5bNumEndpoints 1bInterfaceClass 14bInterfaceSubClass 2bInterfaceProtocol 0iInterface 0Endpoint Descriptor:bLength 7bDescriptorType 5bEndpointAddress 0x82 EP 2 INbmAttributes 5Transfer Type IsochronousSynch Type AsynchronousUsage Type DatawMaxPacketSize 0x0320 1x 800 bytesbInterval 1Interface Descriptor altsetting 6:bLength 9bDescriptorType 4bInterfaceNumber 1bAlternateSetting 6bNumEndpoints 1bInterfaceClass 14bInterfaceSubClass 2bInterfaceProtocol 0iInterface 0Endpoint Descriptor:bLength 7bDescriptorType 5bEndpointAddress 0x82 EP 2 INbmAttributes 5Transfer Type IsochronousSynch Type AsynchronousUsage Type DatawMaxPacketSize 0x03bc 1x 956 bytesbInterval 1extra buffer of interface 1:extra desc 0: 0e 24 01 01 79 00 82 00 02 00 00 01 01 00 extra desc 1: 0b 24 06 01 03 00 01 00 00 00 00 extra desc 2: 1e 24 07 01 01 80 02 e0 01 00 28 23 00 00 28 23 00 00 2c 01 00 15 16 05 00 01 15 16 05 00 extra desc 3: 1e 24 07 02 01 40 01 f0 00 00 ca 08 00 00 ca 08 00 00 4b 00 00 15 16 05 00 01 15 16 05 00 extra desc 4: 1e 24 07 03 01 a0 00 78 00 80 32 02 00 80 32 02 00 c0 12 00 00 15 16 05 00 01 15 16 05 00 extra desc 5: 06 24 0d 01 01 04 VideoStreaming Interface Descriptor:bLength 14bDescriptorType 36bDescriptorSubtype 1 (INPUT_HEADER)bNumFormats 1wTotalLength 121bEndPointAddress 130bmInfo 0bTerminalLink 2bStillCaptureMethod 0bTriggerSupport 0bTriggerUsage 1bControlSize 1bmaControls( 0) 11VideoStreaming Interface Descriptor:bLength 11bDescriptorType 36bDescriptorSubtype 6 (FORMAT_MJPEG)bFormatIndex 1bNumFrameDescriptors 3bFlags 0Fixed-size samples: NobDefaultFrameIndex 1bAspectRatioX 0bAspectRatioY 0bmInterlaceFlags 0x00Interlaced stream or variable: NoFields per frame: 1 fieldsField 1 first: NoField pattern: Field 1 onlybCopyProtect 0VideoStreaming Interface Descriptor:bLength 30bDescriptorType 36bDescriptorSubtype 7 (FRAME_MJPEG)bFrameIndex 1bmCapabilities 0x01Still image supportedwWidth 640wHeight 480dwMinBitRate 2304000dwMaxBitRate 2304000dwMaxVideoFrameBufferSize 76800dwDefaultFrameInterval 333333bFrameIntervalType 1dwFrameInterval( 0) 333333VideoStreaming Interface Descriptor:bLength 30bDescriptorType 36bDescriptorSubtype 7 (FRAME_MJPEG)bFrameIndex 2bmCapabilities 0x01Still image supportedwWidth 320wHeight 240dwMinBitRate 576000dwMaxBitRate 576000dwMaxVideoFrameBufferSize 19200dwDefaultFrameInterval 333333bFrameIntervalType 1dwFrameInterval( 0) 333333VideoStreaming Interface Descriptor:bLength 30bDescriptorType 36bDescriptorSubtype 7 (FRAME_MJPEG)bFrameIndex 3bmCapabilities 0x01Still image supportedwWidth 160wHeight 120dwMinBitRate 144000dwMaxBitRate 144000dwMaxVideoFrameBufferSize 4800dwDefaultFrameInterval 333333bFrameIntervalType 1dwFrameInterval( 0) 333333VideoStreaming Interface Descriptor:bLength 6bDescriptorType 36bDescriptorSubtype 13 (COLORFORMAT)bColorPrimaries 1 (BT.709,sRGB)bTransferCharacteristics 1 (BT.709)bMatrixCoefficients 4 (SMPTE 170M (BT.601))
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