Linux驱动编程 - UVC驱动分析
目录
简介：
一、UVC源码分析
1、uvc_probe() 分析
1.1 uvc_parse_control() 解析设备的控制描述符
uvc_parse_control(dev) 运行步骤：
1.2 V4L2设备注册
1.3 uvc_ctrl_init_device() 初始化uvc控制设备
1.4 uvc_scan_device 扫描设备查找video链
1.5 UVC video驱动注册
1.6 uvc_status_init() 状态初始化
2、总结
简介：
UVC全称为USB Video Class，即：USB视频类，是一种为USB视频捕获设备定义的协议标准。
Linux 已提供UVC设备驱动，因此符合UVC规格的硬件设备在不需要安装任何的驱动程序下即可在主机中正常运行。使用UVC技术的包括摄像头、数码相机等设备。
UVC设备其实就是基于USB框架的V4L2，在Linux系统中属于V4L2设备，它通过V4L2提供的统一API供上层应用进行调用及控制。所以一个UVC设备想要正常显示，必须满足以下几个条件：
- UVC Camera设备的硬件支持
- UVC驱动支持，包括USB设备驱动(UVC)及V4L2驱动的支持
- 上层的应用程序支持，调用V4L2相关的API
一、UVC源码分析
源码路径：drivers/media/usb/uvc/uvc_driver.c
struct uvc_driver uvc_driver = {
.driver = {
.name = "uvcvideo",
.probe = uvc_probe, //支持的usb video设备插入就会调用此probe函数
.disconnect = uvc_disconnect,
.suspend = uvc_suspend,
.resume = uvc_resume,
.reset_resume = uvc_reset_resume,
.id_table = uvc_ids,
.supports_autosuspend = https://img-home.csdnimg.cn/images/20230724024https%3A%2F%2Fimg-home.csdnimg.cn%2Fimages%2F20230724024159.png%3Forigin_url%3D1%26pos_id%3DtpXrtfpc59.png?origin_url=https%3A%2F%2Fimg-home.csdnimg.cn%2Fimages%2F20230724024159.png%3Forigin_url%3D1%26pos_id%3DtpXrtfpc&pos_id=tpXrtfpc,
},
};
// UVC驱动入口
static int __init uvc_init(void)
{
int ret;
uvc_debugfs_init();
//注册一个usb接口（interface）驱动
ret = usb_register(&uvc_driver.driver);
if (ret < 0) {
uvc_debugfs_cleanup();
return ret;
}
printk(KERN_INFO DRIVER_DESC " (" DRIVER_VERSION ")\n");
return 0;
}
// UVC驱动出口
static void __exit uvc_cleanup(void)
{
usb_deregister(&uvc_driver.driver);
uvc_debugfs_cleanup();
}
module_init(uvc_init);
module_exit(uvc_cleanup);insmod加载该驱动程序后，会在入口函数直接注册usb_drvier结构体，通过比较设备提供的Vendor ID（供应商ID）和Product ID（产品ID），和id_table比较，若匹配，则表明驱动支持该usb，或者匹配 USB_INTERFACE_INFO(USB_CLASS_VIDEO, 1, 0) 通用控制接口类。uvc驱动的 usb_device_id 如下所示：
static struct usb_device_id uvc_ids[] = {
/* LogiLink Wireless Webcam */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x0416,
.idProduct = 0xa91a,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
/* Genius eFace 2025 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x0458,
.idProduct = 0x706e,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
/* Microsoft Lifecam NX-6000 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x045e,
.idProduct = 0x00f8,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
/* Microsoft Lifecam NX-3000 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x045e,
.idProduct = 0x0721,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_DEF },
/* Microsoft Lifecam VX-7000 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x045e,
.idProduct = 0x0723,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
/* Logitech Quickcam Fusion */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x046d,
.idProduct = 0x08c1,
.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0 },
/* Logitech Quickcam Orbit MP */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x046d,
.idProduct = 0x08c2,
.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0 },
/* Logitech Quickcam Pro for Notebook */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x046d,
.idProduct = 0x08c3,
.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0 },
/* Logitech Quickcam Pro 5000 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x046d,
.idProduct = 0x08c5,
.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0 },
/* Logitech Quickcam OEM Dell Notebook */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x046d,
.idProduct = 0x08c6,
.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0 },
/* Logitech Quickcam OEM Cisco VT Camera II */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x046d,
.idProduct = 0x08c7,
.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0 },
/* Logitech HD Pro Webcam C920 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x046d,
.idProduct = 0x082d,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_RESTORE_CTRLS_ON_INIT },
/* Chicony CNF7129 (Asus EEE 100HE) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x04f2,
.idProduct = 0xb071,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_RESTRICT_FRAME_RATE },
/* Alcor Micro AU3820 (Future Boy PC USB Webcam) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x058f,
.idProduct = 0x3820,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
/* Dell XPS m1530 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x05a9,
.idProduct = 0x2640,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_DEF },
/* Dell SP2008WFP Monitor */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x05a9,
.idProduct = 0x2641,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_DEF },
/* Dell Alienware X51 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x05a9,
.idProduct = 0x2643,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_DEF },
/* Dell Studio Hybrid 140g (OmniVision webcam) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x05a9,
.idProduct = 0x264a,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_DEF },
/* Dell XPS M1330 (OmniVision OV7670 webcam) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x05a9,
.idProduct = 0x7670,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_DEF },
/* Apple Built-In iSight */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x05ac,
.idProduct = 0x8501,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX
| UVC_QUIRK_BUILTIN_ISIGHT },
/* Foxlink ("HP Webcam" on HP Mini 5103) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x05c8,
.idProduct = 0x0403,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_FIX_BANDWIDTH },
/* Genesys Logic USB 2.0 PC Camera */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x05e3,
.idProduct = 0x0505,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_STREAM_NO_FID },
/* Hercules Classic Silver */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x06f8,
.idProduct = 0x300c,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_FIX_BANDWIDTH },
/* ViMicro Vega */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x0ac8,
.idProduct = 0x332d,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_FIX_BANDWIDTH },
/* ViMicro - Minoru3D */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x0ac8,
.idProduct = 0x3410,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_FIX_BANDWIDTH },
/* ViMicro Venus - Minoru3D */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x0ac8,
.idProduct = 0x3420,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_FIX_BANDWIDTH },
/* Ophir Optronics - SPCAM 620U */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x0bd3,
.idProduct = 0x0555,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
/* MT6227 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x0e8d,
.idProduct = 0x0004,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX
| UVC_QUIRK_PROBE_DEF },
/* IMC Networks (Medion Akoya) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x13d3,
.idProduct = 0x5103,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_STREAM_NO_FID },
/* JMicron USB2.0 XGA WebCam */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x152d,
.idProduct = 0x0310,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
/* Syntek (HP Spartan) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x174f,
.idProduct = 0x5212,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_STREAM_NO_FID },
/* Syntek (Samsung Q310) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x174f,
.idProduct = 0x5931,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_STREAM_NO_FID },
/* Syntek (Packard Bell EasyNote MX52 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x174f,
.idProduct = 0x8a12,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_STREAM_NO_FID },
/* Syntek (Asus F9SG) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x174f,
.idProduct = 0x8a31,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_STREAM_NO_FID },
/* Syntek (Asus U3S) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x174f,
.idProduct = 0x8a33,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_STREAM_NO_FID },
/* Syntek (JAOtech Smart Terminal) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x174f,
.idProduct = 0x8a34,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_STREAM_NO_FID },
/* Miricle 307K */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x17dc,
.idProduct = 0x0202,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_STREAM_NO_FID },
/* Lenovo Thinkpad SL400/SL500 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x17ef,
.idProduct = 0x480b,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_STREAM_NO_FID },
/* Aveo Technology USB 2.0 Camera */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x1871,
.idProduct = 0x0306,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX
| UVC_QUIRK_PROBE_EXTRAFIELDS },
/* Aveo Technology USB 2.0 Camera (Tasco USB Microscope) */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x1871,
.idProduct = 0x0516,
.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0 },
/* Ecamm Pico iMage */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x18cd,
.idProduct = 0xcafe,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_EXTRAFIELDS },
/* Manta MM-353 Plako */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x18ec,
.idProduct = 0x3188,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
/* FSC WebCam V30S */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x18ec,
.idProduct = 0x3288,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
/* Arkmicro unbranded */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x18ec,
.idProduct = 0x3290,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_DEF },
/* The Imaging Source USB CCD cameras */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x199e,
.idProduct = 0x8102,
.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0 },
/* Bodelin ProScopeHR */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_DEV_HI
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x19ab,
.idProduct = 0x1000,
.bcdDevice_hi = 0x0126,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_STATUS_INTERVAL },
/* MSI StarCam 370i */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x1b3b,
.idProduct = 0x2951,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
/* SiGma Micro USB Web Camera */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x1c4f,
.idProduct = 0x3000,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX
| UVC_QUIRK_IGNORE_SELECTOR_UNIT },
/* Oculus VR Positional Tracker DK2 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
.idVendor = 0x2833,
.idProduct = 0x0201,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_FORCE_Y8 },
/* Generic USB Video Class */
{ USB_INTERFACE_INFO(USB_CLASS_VIDEO, 1, 0) },
{}
};USB_INTERFACE_INFO 宏定义在 include\linux\usb.h
/**
* USB_INTERFACE_INFO - macro used to describe a class of usb interfaces
* @cl: bInterfaceClass value
* @sc: bInterfaceSubClass value
* @pr: bInterfaceProtocol value
*
* This macro is used to create a struct usb_device_id that matches a
* specific class of interfaces.
*/
#define USB_INTERFACE_INFO(cl, sc, pr) \
.match_flags = USB_DEVICE_ID_MATCH_INT_INFO, \
.bInterfaceClass = (cl), \
.bInterfaceSubClass = (sc), \
.bInterfaceProtocol = (pr)当有对应的UVC摄像头插入时，会调用 .probe函数。 uvc_probe中实现V4L2的那一套流程应该就能正常工作了。
1）分配 video_device 结构体
2）配置 video_device 结构体，设置 fops、ioctl_ops 操作集
3）video_register_device() 注册 video_device 结构体
USB描述符结构体参考：Linux子系统 - USB描述符结构体-CSDN博客
1、uvc_probe() 分析
当一个USB设备插入系统被响应后，最先是通用usb驱动进行初步识别，确认是一个usb设备后，再通过读取配置描述符，进一步确认该设备是那种usb class device(如HID、MassStorage、UVC等)。 一旦通过配置信息知道属于那种设备类后，将会进行调用对应的usb interface driver进行匹配设备驱动。如果是UVC设备被匹配成功后将会调用对应的接口驱动的probe函数进行设备注册功能。
uvc_probe() 主要做了几件事情：
（1）分配一个dev
（2）设置dev参数，如：dev->udev = usb_get_dev(udev)
（3）调用 uvc_parse_control() 解析设备的控制描述符
（4）调用 v4l2_device_register() 初始化v4l2_dev
（5）调用 uvc_ctrl_init_device() 初始化uvc控制设备
（6）调用 uvc_register_chains() 注册所有通道（注册 video_device）
（7）调用 uvc_status_init() 初始化uvc状态
static int uvc_probe(struct usb_interface *intf,
const struct usb_device_id *id)
{
struct usb_device *udev = interface_to_usbdev(intf); //通过usb_interface 获取 usb_device
struct uvc_device *dev;
int ret;
/* 打印VID 和 PID信息 */
if (id->idVendor && id->idProduct)
uvc_trace(UVC_TRACE_PROBE, "Probing known UVC device %s "
"(%04x:%04x)\n", udev->devpath, id->idVendor,
id->idProduct);
else
uvc_trace(UVC_TRACE_PROBE, "Probing generic UVC device %s\n",
udev->devpath);
/* https://img-home.csdnimg.cn/images/20230724024https%3A%2F%2Fimg-home.csdnimg.cn%2Fimages%2F20230724024159.png%3Forigin_url%3D1%26pos_id%3DtpXrtfpc59.png?origin_url=https%3A%2F%2Fimg-home.csdnimg.cn%2Fimages%2F20230724024159.png%3Forigin_url%3D1%26pos_id%3DtpXrtfpc&pos_id=tpXrtfpc.分配 uvc_device */
if ((dev = kzalloc(sizeof *dev, GFP_KERNEL)) == NULL)
return -ENOMEM;
/* ... ... */
/* 2.配置 uvc_device */
dev->udev = usb_get_dev(udev); //udev
dev->intf = usb_get_intf(intf);
dev->intfnum = intf->cur_altsetting->desc.bInterfaceNumber;
dev->quirks = (uvc_quirks_param == -https://img-home.csdnimg.cn/images/20230724024https%3A%2F%2Fimg-home.csdnimg.cn%2Fimages%2F20230724024159.png%3Forigin_url%3D1%26pos_id%3DtpXrtfpc59.png?origin_url=https%3A%2F%2Fimg-home.csdnimg.cn%2Fimages%2F20230724024159.png%3Forigin_url%3D1%26pos_id%3DtpXrtfpc&pos_id=tpXrtfpc)
? id->driver_info : uvc_quirks_param;
if (udev->product != NULL)
strlcpy(dev->name, udev->product, sizeof dev->name);
else
snprintf(dev->name, sizeof dev->name,
"UVC Camera (%04x:%04x)",
lehttps://img-home.csdnimg.cn/images/20230724024https%3A%2F%2Fimg-home.csdnimg.cn%2Fimages%2F20230724024159.png%3Forigin_url%3D1%26pos_id%3DtpXrtfpc59.png?origin_url=https%3A%2F%2Fimg-home.csdnimg.cn%2Fimages%2F20230724024159.png%3Forigin_url%3D1%26pos_id%3DtpXrtfpc&pos_id=tpXrtfpc6_to_cpu(udev->descriptor.idVendor),
lehttps://img-home.csdnimg.cn/images/20230724024https%3A%2F%2Fimg-home.csdnimg.cn%2Fimages%2F20230724024159.png%3Forigin_url%3D1%26pos_id%3DtpXrtfpc59.png?origin_url=https%3A%2F%2Fimg-home.csdnimg.cn%2Fimages%2F20230724024159.png%3Forigin_url%3D1%26pos_id%3DtpXrtfpc&pos_id=tpXrtfpc6_to_cpu(udev->descriptor.idProduct));
/* 3.解析Video Class的控制描述符 */
/* Parse the Video Class control descriptor. */
if (uvc_parse_control(dev) < 0) {
uvc_trace(UVC_TRACE_PROBE, "Unable to parse UVC "
"descriptors.\n");
goto error;
}
/* 4.初始化v4l2_device */
if (v4l2_device_register(&intf->dev, &dev->vdev) < 0)
goto error;
/* 5.初始化UVC控制设备 */
/* Initialize controls. */
if (uvc_ctrl_init_device(dev) < 0)
goto error;
/* Scan the device for video chains. */
if (uvc_scan_device(dev) < 0)
goto error;
/* 6.注册所有通道 */
/* Register video device nodes. */
if (uvc_register_chains(dev) < 0)
goto error;
/* Save our data pointer in the interface data. */
usb_set_intfdata(intf, dev);
/* 7.初始化UVC状态，UVC状态的处理由中断端点来控制处理 */
/* Initialize the interrupt URB. */
if ((ret = uvc_status_init(dev)) < 0) {
uvc_printk(KERN_INFO, "Unable to initialize the status "
"endpoint (%d), status interrupt will not be "
"supported.\n", ret);
}
uvc_trace(UVC_TRACE_PROBE, "UVC device initialized.\n");
usb_enable_autosuspend(udev);
return 0;
error:
uvc_unregister_video(dev);
return -ENODEV;
}1.1 uvc_parse_control() 解析设备的控制描述符
uvc_parse_control(dev) 运行步骤：
uvc_parse_control(dev)
--->uvc_parse_standard_control(dev, buffer, buflen)// 解析类特定视频控制描述符，并找到视频流接口描述符
--->--->uvc_parse_streaming(dev, intf) // 解析视频流接口描述符及类特定视频流接口描述符
--->--->--->uvc_parse_format() // 解析format和frameuvc_parse_control 分析
static int uvc_parse_control(struct uvc_device *dev)
{
// 首先，拿到当前使用的interface descriptor接口描述符
struct usb_host_interface *alts = dev->intf->cur_altsetting;
// 其次，拿到扩展描述符信息。 alts->extra存放的是类特定描述符，此处为类特定视频控制接口描述符class-specific VC interface descriptor
unsigned char *buffer = alts->extra;
int buflen = alts->extralen;
int ret;
/* Parse the default alternate setting only, as the UVC specification
* defines a single alternate setting, the default alternate setting
* zero.
*/
while (buflen > 2) {
if (uvc_parse_vendor_control(dev, buffer, buflen) ||
buffer[1] != USB_DT_CS_INTERFACE)
goto next_descriptor;
// 开始逐个解析类特定视频控制接口描述符class-specific VC interface descriptor，主要解析所有的video function：
// UVC_VC_HEADER\UVC_VC_INPUT_TERMINAL\UVC_VC_OUTPUT_TERMINAL\UVC_VC_SELECTOR_UNIT
// UVC_VC_PROCESSING_UNITUVC_VC_EXTENSION_UNIT
if ((ret = uvc_parse_standard_control(dev, buffer, buflen)) < 0)
return ret;
next_descriptor:
buflen -= buffer[0];
buffer += buffer[0];
}
/* Check if the optional status endpoint is present. Built-in iSight
* webcams have an interrupt endpoint but spit proprietary data that
* don't conform to the UVC status endpoint messages. Don't try to
* handle the interrupt endpoint for those cameras.
*/
if (alts->desc.bNumEndpoints == 1 &&
!(dev->quirks & UVC_QUIRK_BUILTIN_ISIGHT)) {
struct usb_host_endpoint *ep = &alts->endpoint[0];
struct usb_endpoint_descriptor *desc = &ep->desc;
if (usb_endpoint_is_int_in(desc) &&
le16_to_cpu(desc->wMaxPacketSize) >= 8 &&
desc->bInterval != 0) {
uvc_trace(UVC_TRACE_DESCR, "Found a Status endpoint "
"(addr %02x).\n", desc->bEndpointAddress);
dev->int_ep = ep;
}
}
return 0;
}
uvc_parse_standard_control() 主要是对类特定的视频控制接口所描述的所有video function进行解析。主要分析 UVC_VC_HEADER的解析流程
static int uvc_parse_standard_control(struct uvc_device *dev,
const unsigned char *buffer, int buflen)
{
struct usb_device *udev = dev->udev;
struct uvc_entity *unit, *term;
struct usb_interface *intf;
struct usb_host_interface *alts = dev->intf->cur_altsetting;
unsigned int i, n, p, len;
__u16 type;
// 由前面我们知道，这个buffer是存放类特定视频控制描述符的。 它的布局通常第一个存放的就是VC_HEADER.
switch (buffer[2]) {
case UVC_VC_HEADER:
// 得到当前的UVC设备，有多少个VS视频流接口Video Streaming Interface数量
n = buflen >= 12 ? buffer[11] : 0;
if (buflen < 12 + n) {
uvc_trace(UVC_TRACE_DESCR, "device %d videocontrol "
"interface %d HEADER error\n", udev->devnum,
alts->desc.bInterfaceNumber);
return -EINVAL;
}
// 根据VC_HEADER描述符提取相应的字段
dev->uvc_version = get_unaligned_le16(&buffer[3]);
dev->clock_frequency = get_unaligned_le32(&buffer[7]);
/* Parse all USB Video Streaming interfaces. */
// 根据得到的视频流接口个数，依次遍历解析所有的VS视频流接口
for (i = 0; i < n; ++i) {
// 根据指定的视频流接口号'baInterfaceNr[i]'，获取对应的接口信息描述符
intf = usb_ifnum_to_if(udev, buffer[12+i]);
if (intf == NULL) {
uvc_trace(UVC_TRACE_DESCR, "device %d "
"interface %d doesn't exists\n",
udev->devnum, i);
continue;
}
// 解析video streaming interface描述符，主要是从类特定视频流接口描述符中解析。
uvc_parse_streaming(dev, intf);
}
break;
case UVC_VC_INPUT_TERMINAL:
...
break;
case UVC_VC_OUTPUT_TERMINAL:
...
break;
case UVC_VC_SELECTOR_UNIT:
...
break;
case UVC_VC_PROCESSING_UNIT:
...
break;
case UVC_VC_EXTENSION_UNIT:
...
break;
default:
uvc_trace(UVC_TRACE_DESCR, "Found an unknown CS_INTERFACE "
"descriptor (%u)\n", buffer[2]);
break;
}
return 0;
}
uvc_parse_streaming(dev, intf) 主要是从Video Streaming Interface Descriptor中与之相关的类特定视频流接口描述符 (Class-Specific VS Interface Descriptors)里面进行解析与视频流有关的Input and Output Header Descriptor，并从它们中解析出视频格式(Format Descriptor)和帧格式(Frame Descriptor)。
//函数传进来的intf就是一个usb_interface数据结构，它包含了一个视频流接口描述符video streaming interface，即usb_host_interface
static int uvc_parse_streaming(struct uvc_device *dev,
struct usb_interface *intf)
{
struct uvc_streaming *streaming = NULL;
struct uvc_format *format;
struct uvc_frame *frame;
// 得到一个视频流接口描述符
struct usb_host_interface *alts = &intf->altsetting[0];
// 得到当前视频流接口描述符与之对应的类特定视频流接口描述符
unsigned char *_buffer, *buffer = alts->extra;
int _buflen, buflen = alts->extralen;
unsigned int nformats = 0, nframes = 0, nintervals = 0;
unsigned int size, i, n, p;
__u32 *interval;
__u16 psize;
int ret = -EINVAL;
// 判断该接口是否是视频流接口描述符
if (intf->cur_altsetting->desc.bInterfaceSubClass
!= UVC_SC_VIDEOSTREAMING) {
uvc_trace(UVC_TRACE_DESCR, "device %d interface %d isn't a "
"video streaming interface\n", dev->udev->devnum,
intf->altsetting[0].desc.bInterfaceNumber);
return -EINVAL;
}
if (usb_driver_claim_interface(&uvc_driver.driver, intf, dev)) {
uvc_trace(UVC_TRACE_DESCR, "device %d interface %d is already "
"claimed\n", dev->udev->devnum,
intf->altsetting[0].desc.bInterfaceNumber);
return -EINVAL;
}
// uvc_streaming数据结构，很重要，包含了该设备所有的视频流接口信息，大部分参数都是存在里面，如支持有多少帧格式、支持的帧信息等
streaming = kzalloc(sizeof *streaming, GFP_KERNEL);
if (streaming == NULL) {
usb_driver_release_interface(&uvc_driver.driver, intf);
return -EINVAL;
}
mutex_init(&streaming->mutex);
streaming->dev = dev;
streaming->intf = usb_get_intf(intf);
// 当前接口的接口号
streaming->intfnum = intf->cur_altsetting->desc.bInterfaceNumber;
/* The Pico iMage webcam has its class-specific interface descriptors
* after the endpoint descriptors.
*/
if (buflen == 0) {
for (i = 0; i < alts->desc.bNumEndpoints; ++i) {
struct usb_host_endpoint *ep = &alts->endpoint[i];
if (ep->extralen == 0)
continue;
if (ep->extralen > 2 &&
ep->extra[1] == USB_DT_CS_INTERFACE) {
uvc_trace(UVC_TRACE_DESCR, "trying extra data "
"from endpoint %u.\n", i);
buffer = alts->endpoint[i].extra;
buflen = alts->endpoint[i].extralen;
break;
}
}
}
/* Skip the standard interface descriptors. */
while (buflen > 2 && buffer[1] != USB_DT_CS_INTERFACE /* 0x24 */) {
buflen -= buffer[0];
buffer += buffer[0];
}
if (buflen <= 2) {
uvc_trace(UVC_TRACE_DESCR, "no class-specific streaming "
"interface descriptors found.\n");
goto error;
}
/* Parse the header descriptor. */
switch (buffer[2]) {
case UVC_VS_OUTPUT_HEADER:
streaming->type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
size = 9;
break;
// 对应UVC相机设备，是一个输入设备Capture
case UVC_VS_INPUT_HEADER:
streaming->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
// INPUT_HEADER能确定的固定大小是13
size = 13;
break;
default:
uvc_trace(UVC_TRACE_DESCR, "device %d videostreaming interface "
"%d HEADER descriptor not found.\n", dev->udev->devnum,
alts->desc.bInterfaceNumber);
goto error;
}
// 此接口支持的帧格式数量
p = buflen >= 4 ? buffer[3] : 0;
// 获取‘bControlSize’字段的大小
n = buflen >= size ? buffer[size-1] : 0;
if (buflen < size + p*n) {
uvc_trace(UVC_TRACE_DESCR, "device %d videostreaming "
"interface %d HEADER descriptor is invalid.\n",
dev->udev->devnum, alts->desc.bInterfaceNumber);
goto error;
}
// 此接口支持的帧格式个数
streaming->header.bNumFormats = p;
streaming->header.bEndpointAddress = buffer[6];
// 根据Input header descriptor获取相应字段信息
if (buffer[2] == UVC_VS_INPUT_HEADER) {
streaming->header.bmInfo = buffer[7];
streaming->header.bTerminalLink = buffer[8];
streaming->header.bStillCaptureMethod = buffer[9];
streaming->header.bTriggerSupport = buffer[10];
streaming->header.bTriggerUsage = buffer[11];
} else {
streaming->header.bTerminalLink = buffer[7];
}
streaming->header.bControlSize = n;
streaming->header.bmaControls = kmemdup(&buffer[size], p * n,
GFP_KERNEL);
if (streaming->header.bmaControls == NULL) {
ret = -ENOMEM;
goto error;
}
// 跳过 Input Header Descpritor, 后面一般紧跟着的就是format和frame的描述符
buflen -= buffer[0];
buffer += buffer[0];
// 临时变量，为变量出有多少个format和frame临时设置
_buffer = buffer;
_buflen = buflen;
/* Count the format and frame descriptors. */
while (_buflen > 2 && _buffer[1] == USB_DT_CS_INTERFACE) {
switch (_buffer[2]) {
case UVC_VS_FORMAT_UNCOMPRESSED:
case UVC_VS_FORMAT_MJPEG:
case UVC_VS_FORMAT_FRAME_BASED:
nformats++;
break;
case UVC_VS_FORMAT_DV:
/* DV format has no frame descriptor. We will create a
* dummy frame descriptor with a dummy frame interval.
*/
nformats++;
nframes++;
nintervals++;
break;
case UVC_VS_FORMAT_MPEG2TS:
case UVC_VS_FORMAT_STREAM_BASED:
uvc_trace(UVC_TRACE_DESCR, "device %d videostreaming "
"interface %d FORMAT %u is not supported.\n",
dev->udev->devnum,
alts->desc.bInterfaceNumber, _buffer[2]);
break;
case UVC_VS_FRAME_UNCOMPRESSED:
case UVC_VS_FRAME_MJPEG:
nframes++;
if (_buflen > 25)
nintervals += _buffer[25] ? _buffer[25] : 3;
break;
case UVC_VS_FRAME_FRAME_BASED:
nframes++;
if (_buflen > 21)
nintervals += _buffer[21] ? _buffer[21] : 3;
break;
}
_buflen -= _buffer[0];
_buffer += _buffer[0];
}
if (nformats == 0) {
uvc_trace(UVC_TRACE_DESCR, "device %d videostreaming interface "
"%d has no supported formats defined.\n",
dev->udev->devnum, alts->desc.bInterfaceNumber);
goto error;
}
// 上面的while循环是依次遍历当前接口包含多少Format及frame描述符，然后进行资源分配
size = nformats * sizeof *format + nframes * sizeof *frame
+ nintervals * sizeof *interval;
format = kzalloc(size, GFP_KERNEL);
if (format == NULL) {
ret = -ENOMEM;
goto error;
}
frame = (struct uvc_frame *)&format[nformats];
interval = (__u32 *)&frame[nframes];
streaming->format = format;
streaming->nformats = nformats;
/* Parse the format descriptors. */
// 依次遍历解析该接口所有的format descriptor
// 此刻的buffer是指向Input Header descriptor的下一个描述符，即Format Descriptor
while (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE) {
switch (buffer[2]) {
case UVC_VS_FORMAT_UNCOMPRESSED:
case UVC_VS_FORMAT_MJPEG:
case UVC_VS_FORMAT_DV:
case UVC_VS_FORMAT_FRAME_BASED:
format->frame = frame;
// 解析format descriptor
ret = uvc_parse_format(dev, streaming, format,
&interval, buffer, buflen);
if (ret < 0)
goto error;
frame += format->nframes;
format++;
buflen -= ret;
buffer += ret;
continue;
default:
break;
}
buflen -= buffer[0];
buffer += buffer[0];
}
if (buflen)
uvc_trace(UVC_TRACE_DESCR, "device %d videostreaming interface "
"%d has %u bytes of trailing descriptor garbage.\n",
dev->udev->devnum, alts->desc.bInterfaceNumber, buflen);
/* Parse the alternate settings to find the maximum bandwidth. */
for (i = 0; i < intf->num_altsetting; ++i) {
struct usb_host_endpoint *ep;
alts = &intf->altsetting[i];
ep = uvc_find_endpoint(alts,
streaming->header.bEndpointAddress);
if (ep == NULL)
continue;
psize = le16_to_cpu(ep->desc.wMaxPacketSize);
psize = (psize & 0x07ff) * (1 + ((psize >> 11) & 3));
if (psize > streaming->maxpsize)
streaming->maxpsize = psize;
}
// 最后将streaming添加到streams链表中
list_add_tail(&streaming->list, &dev->streams);
return 0;
error:
usb_driver_release_interface(&uvc_driver.driver, intf);
usb_put_intf(intf);
kfree(streaming->format);
kfree(streaming->header.bmaControls);
kfree(streaming);
return ret;
}
uvc_parse_format() 函数，它主要是解析Format Descriptor信息后，在解析对应的frame descriptor信息并分别记录到对应的format和frame数据结构中，然后让streaming统一管理，为后续使用准备
/* ------------------------------------------------------------------------
* Descriptors parsing
*/
static int uvc_parse_format(struct uvc_device *dev,
struct uvc_streaming *streaming, struct uvc_format *format,
__u32 **intervals, unsigned char *buffer, int buflen)
{
struct usb_interface *intf = streaming->intf;
struct usb_host_interface *alts = intf->cur_altsetting;
struct uvc_format_desc *fmtdesc;
struct uvc_frame *frame;
const unsigned char *start = buffer;
unsigned int width_multiplier = 1;
unsigned int interval;
unsigned int i, n;
__u8 ftype;
// 传进来的buffer一定是一个Format Descriptor，要根据不同的format查看对应的payload document
format->type = buffer[2];
format->index = buffer[3];
// 进行匹配对应的formt，并提取对应字段，没什么比较简单
switch (buffer[2]) {
case UVC_VS_FORMAT_UNCOMPRESSED:
case UVC_VS_FORMAT_FRAME_BASED:
n = buffer[2] == UVC_VS_FORMAT_UNCOMPRESSED ? 27 : 28;
if (buflen < n) {
uvc_trace(UVC_TRACE_DESCR, "device %d videostreaming "
"interface %d FORMAT error\n",
dev->udev->devnum,
alts->desc.bInterfaceNumber);
return -EINVAL;
}
/* Find the format descriptor from its GUID. */
fmtdesc = uvc_format_by_guid(&buffer[5]);
if (fmtdesc != NULL) {
strlcpy(format->name, fmtdesc->name,
sizeof format->name);
format->fcc = fmtdesc->fcc;
} else {
uvc_printk(KERN_INFO, "Unknown video format %pUl\n",
&buffer[5]);
snprintf(format->name, sizeof(format->name), "%pUl\n",
&buffer[5]);
format->fcc = 0;
}
format->bpp = buffer[21];
/* Some devices report a format that doesn't match what they
* really send.
*/
if (dev->quirks & UVC_QUIRK_FORCE_Y8) {
if (format->fcc == V4L2_PIX_FMT_YUYV) {
strlcpy(format->name, "Greyscale 8-bit (Y8 )",
sizeof(format->name));
format->fcc = V4L2_PIX_FMT_GREY;
format->bpp = 8;
width_multiplier = 2;
}
}
if (buffer[2] == UVC_VS_FORMAT_UNCOMPRESSED) {
ftype = UVC_VS_FRAME_UNCOMPRESSED;
} else {
ftype = UVC_VS_FRAME_FRAME_BASED;
if (buffer[27])
format->flags = UVC_FMT_FLAG_COMPRESSED;
}
break;
case UVC_VS_FORMAT_MJPEG:
if (buflen < 11) {
uvc_trace(UVC_TRACE_DESCR, "device %d videostreaming "
"interface %d FORMAT error\n",
dev->udev->devnum,
alts->desc.bInterfaceNumber);
return -EINVAL;
}
strlcpy(format->name, "MJPEG", sizeof format->name);
format->fcc = V4L2_PIX_FMT_MJPEG;
format->flags = UVC_FMT_FLAG_COMPRESSED;
format->bpp = 0;
ftype = UVC_VS_FRAME_MJPEG;
break;
case UVC_VS_FORMAT_DV:
...
break;
case UVC_VS_FORMAT_MPEG2TS:
case UVC_VS_FORMAT_STREAM_BASED:
/* Not supported yet. */
default:
uvc_trace(UVC_TRACE_DESCR, "device %d videostreaming "
"interface %d unsupported format %u\n",
dev->udev->devnum, alts->desc.bInterfaceNumber,
buffer[2]);
return -EINVAL;
}
uvc_trace(UVC_TRACE_DESCR, "Found format %s.\n", format->name);
// 指向下一个描述符
buflen -= buffer[0];
buffer += buffer[0];
/* Parse the frame descriptors. Only uncompressed, MJPEG and frame
* based formats have frame descriptors.
*/
// 匹配当前format下的所有frame
while (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE &&
buffer[2] == ftype) {
frame = &format->frame[format->nframes];
...
...
...
// format下的frame，实际上是支持多少中分辨率
format->nframes++;
buflen -= buffer[0];
buffer += buffer[0];
}
...
...
...
return buffer - start;
}
解析完了之后所有的视频流信息都被记录到了struct uvc_device结构体中
struct uvc_device {
struct usb_device *udev;
struct usb_interface *intf;
unsigned long warnings;
__u32 quirks;
int intfnum;
char name[32];
enum uvc_device_state state;
struct mutex lock; /* Protects users */
unsigned int users;
atomic_t nmappings;
/* Video control interface */
#ifdef CONFIG_MEDIA_CONTROLLER
struct media_device mdev;
#endif
struct v4l2_device vdev;
__u16 uvc_version;
__u32 clock_frequency;
struct list_head entities;
struct list_head chains;
/* Video Streaming interfaces */
struct list_head streams;
atomic_t nstreams;
/* Status Interrupt Endpoint */
struct usb_host_endpoint *int_ep;
struct urb *int_urb;
__u8 *status;
struct input_dev *input;
char input_phys[64];
};1.2 V4L2设备注册
v4l2_device_register() 初始化v4l2_dev->subdevs子设备实例的链表，然后设置名字和设置dev->driver_data
int v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev)
{
INIT_LIST_HEAD(&v4l2_dev->subdevs);//用来管理v4l2_device 下的subdevs实例
spin_lock_init(&v4l2_dev->lock);
v4l2_prio_init(&v4l2_dev->prio);
kref_init(&v4l2_dev->ref);
get_device(dev);
v4l2_dev->dev = dev;
if (!v4l2_dev->name[0])
snprintf(v4l2_dev->name, sizeof(v4l2_dev->name), "%s %s",
dev->driver->name, dev_name(dev));
if (!dev_get_drvdata(dev))//dev->driver_data 域 为 NULL
dev_set_drvdata(dev, v4l2_dev);//就将其指向 v4l2_dev
return 0;
}
1.3 uvc_ctrl_init_device() 初始化uvc控制设备
uvc_ctrl_init_device() 初始化控制参数，里面就会遍历uvc设备实体entities链表，然后设置位图和位域大小。调用uvc_ctrl_init_ctrl() 设置背光，色温等等
int uvc_ctrl_init_device(struct uvc_device *dev)
{
/* ... ... */
list_for_each_entry(entity, &dev->entities, list) {
bmControls = entity->extension.bmControls; //控制位图
bControlSize = entity->extension.bControlSize; //控制位域大小
entity->controls = kcalloc(ncontrols, sizeof(*ctrl),
GFP_KERNEL); //分配ncontrols个uvc控制内存
if (entity->controls == NULL)
return -ENOMEM;
entity->ncontrols = ncontrols; //设置uvc控制个数
/* Initialize all supported controls */
ctrl = entity->controls; //指向uvc控制数组
for (i = 0; i < bControlSize * 8; ++i) {
if (uvc_test_bit(bmControls, i) == 0) //跳过控制位域设置0的
continue;
ctrl->entity = entity;
ctrl->index = i; //设置控制位域索引
uvc_ctrl_init_ctrl(dev, ctrl); //初始化uvc控件
ctrl++; //uvc控制 指向下一个uvc控制数组项
}
}
}1.4 uvc_scan_device 扫描设备查找video链
扫描设备以查找video链并注册video设备
static int uvc_scan_device(struct uvc_device *dev)
{
struct uvc_video_chain *chain;
struct uvc_entity *term;
list_for_each_entry(term, &dev->entities, list) {
if (!UVC_ENTITY_IS_OTERM(term))
continue;
/* If the terminal is already included in a chain, skip it.
* This can happen for chains that have multiple output
* terminals, where all output terminals beside the first one
* will be inserted in the chain in forward scans.
*/
if (term->chain.next || term->chain.prev)
continue;
chain = kzalloc(sizeof(*chain), GFP_KERNEL);
if (chain == NULL)
return -ENOMEM;
INIT_LIST_HEAD(&chain->entities);
mutex_init(&chain->ctrl_mutex);
chain->dev = dev;
v4l2_prio_init(&chain->prio);
term->flags |= UVC_ENTITY_FLAG_DEFAULT;
if (uvc_scan_chain(chain, term) < 0) {
kfree(chain);
continue;
}
uvc_trace(UVC_TRACE_PROBE, "Found a valid video chain (%s).\n",
uvc_print_chain(chain));
list_add_tail(&chain->list, &dev->chains); //dev->chains添加 video 设备
}
if (list_empty(&dev->chains)) {
uvc_printk(KERN_INFO, "No valid video chain found.\n");
return -https://img-home.csdnimg.cn/images/20230724024https://img-home.csdnimg.cn/images/20230724024159.png?origin_url=1&pos_id=tpXrtfpc59.png?origin_url=https://img-home.csdnimg.cn/images/20230724024159.png?origin_url=1&pos_id=tpXrtfpc&pos_id=tpXrtfpc;
}
return 0;
}1.5 UVC video驱动注册
uvc_register_chains() 运行过程
uvc_register_chains
uvc_register_terms(dev, chain)
uvc_stream_by_id
uvc_register_video
uvc_mc_register_entities(chain)uvc_register_chains() 函数
static int uvc_register_chains(struct uvc_device *dev)
{
struct uvc_video_chain *chain;
int ret;
/* 轮询 dev->chains */
list_for_each_entry(chain, &dev->chains, list) {
ret = uvc_register_terms(dev, chain);
if (ret < 0)
return ret;
#ifdef CONFIG_MEDIA_CONTROLLER
ret = uvc_mc_register_entities(chain);
if (ret < 0) {
uvc_printk(KERN_INFO, "Failed to register entites "
"(%d).\n", ret);
}
#endif
}
return 0;
}uvc_register_terms() 注册所有chains中的 video 设备
static int uvc_register_terms(struct uvc_device *dev,
struct uvc_video_chain *chain)
{
struct uvc_streaming *stream;
struct uvc_entity *term;
int ret;
list_for_each_entry(term, &chain->entities, chain) {
if (UVC_ENTITY_TYPE(term) != UVC_TT_STREAMING)
continue;
stream = uvc_stream_by_id(dev, term->id);
if (stream == NULL) {
uvc_printk(KERN_INFO, "No streaming interface found "
"for terminal %u.", term->id);
continue;
}
stream->chain = chain;
ret = uvc_register_video(dev, stream);
if (ret < 0)
return ret;
term->vdev = &stream->vdev;
}
return 0;
}
uvc_stream_by_id() 会通过函数传入的id和dev->streams链表的header.bTerminalLink匹配，寻找到stream。
uvc_register_video() 注册匹配的stream
static int uvc_register_video(struct uvc_device *dev,
struct uvc_streaming *stream)
{
/*... ... */
struct video_device *vdev = &stream->vdev;
ret = uvc_queue_init(&stream->queue, stream->type, !uvc_no_drop_param);//初始化队列
ret = uvc_video_init(stream); //初始化
uvc_debugfs_init_stream(stream);
vdev->v4l2_dev = &dev->vdev;
vdev->fops = &uvc_fops; //v4l2操作函数集
vdev->ioctl_ops = &uvc_ioctl_ops; //设置真正的ioctl操作集
vdev->release = uvc_release;
vdev->prio = &stream->chain->prio;
strlcpy(vdev->name, dev->name, sizeof vdev->name);
video_set_drvdata(vdev, stream); //将uvc视频流作为v4l2设备的驱动数据
ret = video_register_device(vdev, VFL_TYPE_GRABBER, -1); //注册 video_device
return 0;
}
这里就是V4L2注册 video 设备的那套流程，它注册uvc driver驱动。video_register_device() 中创建字符设备，生成uvc节点：/dev/videoX
1.6 uvc_status_init() 状态初始化
int uvc_status_init(struct uvc_device *dev)
{
/* ... ... */
struct usb_host_endpoint *ep = dev->int_ep; //获取usb_host_endpoint
uvc_input_init(dev); //初始化uvc输入设备,里面注册input设备
dev->status = kzalloc(UVC_MAX_STATUS_SIZE, GFP_KERNEL); //分配urb设备状态内存
dev->int_urb = usb_alloc_urb(0, GFP_KERNEL); //分配urb
pipe = usb_rcvintpipe(dev->udev, ep->desc.bEndpointAddress);//中断输入端点
usb_fill_int_urb(dev->int_urb, dev->udev, pipe,
dev->status, UVC_MAX_STATUS_SIZE, uvc_status_complete,
dev, interval); //填充中断urb
return 0;
}
2、总结
（1）uvc_probe()中最重要的其实还是 V4L2子系统注册 video_device 那一套流程
（2）若要自己手撸UVC驱动，v4l2_ioctl_ops 和 v4l2_file_operations 操作集参考 drivers\media\usb\uvc\uvc_v4l2.c 中的内容
const struct v4l2_ioctl_ops uvc_ioctl_ops = {
.vidioc_querycap = uvc_ioctl_querycap,
.vidioc_enum_fmt_vid_cap = uvc_ioctl_enum_fmt_vid_cap,
.vidioc_enum_fmt_vid_out = uvc_ioctl_enum_fmt_vid_out,
.vidioc_g_fmt_vid_cap = uvc_ioctl_g_fmt_vid_cap,
.vidioc_g_fmt_vid_out = uvc_ioctl_g_fmt_vid_out,
.vidioc_s_fmt_vid_cap = uvc_ioctl_s_fmt_vid_cap,
.vidioc_s_fmt_vid_out = uvc_ioctl_s_fmt_vid_out,
.vidioc_try_fmt_vid_cap = uvc_ioctl_try_fmt_vid_cap,
.vidioc_try_fmt_vid_out = uvc_ioctl_try_fmt_vid_out,
.vidioc_reqbufs = uvc_ioctl_reqbufs,
.vidioc_querybuf = uvc_ioctl_querybuf,
.vidioc_qbuf = uvc_ioctl_qbuf,
.vidioc_dqbuf = uvc_ioctl_dqbuf,
.vidioc_create_bufs = uvc_ioctl_create_bufs,
.vidioc_streamon = uvc_ioctl_streamon,
.vidioc_streamoff = uvc_ioctl_streamoff,
.vidioc_enum_input = uvc_ioctl_enum_input,
.vidioc_g_input = uvc_ioctl_g_input,
.vidioc_s_input = uvc_ioctl_s_input,
.vidioc_queryctrl = uvc_ioctl_queryctrl,
.vidioc_query_ext_ctrl = uvc_ioctl_query_ext_ctrl,
.vidioc_g_ctrl = uvc_ioctl_g_ctrl,
.vidioc_s_ctrl = uvc_ioctl_s_ctrl,
.vidioc_g_ext_ctrls = uvc_ioctl_g_ext_ctrls,
.vidioc_s_ext_ctrls = uvc_ioctl_s_ext_ctrls,
.vidioc_try_ext_ctrls = uvc_ioctl_try_ext_ctrls,
.vidioc_querymenu = uvc_ioctl_querymenu,
.vidioc_g_selection = uvc_ioctl_g_selection,
.vidioc_g_parm = uvc_ioctl_g_parm,
.vidioc_s_parm = uvc_ioctl_s_parm,
.vidioc_enum_framesizes = uvc_ioctl_enum_framesizes,
.vidioc_enum_frameintervals = uvc_ioctl_enum_frameintervals,
.vidioc_subscribe_event = uvc_ioctl_subscribe_event,
.vidioc_unsubscribe_event = v4l2_event_unsubscribe,
.vidioc_default = uvc_ioctl_default,
};
const struct v4l2_file_operations uvc_fops = {
.owner = THIS_MODULE,
.open = uvc_v4l2_open,
.release = uvc_v4l2_release,
.unlocked_ioctl = video_ioctl2,
#ifdef CONFIG_COMPAT
.compat_ioctl32 = uvc_v4l2_compat_ioctl32,
#endif
.read = uvc_v4l2_read,
.mmap = uvc_v4l2_mmap,
.poll = uvc_v4l2_poll,
#ifndef CONFIG_MMU
.get_unmapped_area = uvc_v4l2_get_unmapped_area,
#endif
};