linux uvc 驱动架构,UVC 驱动调用过程与驱动框架的简单分析

/*打开设备描述符*/

1. open:

uvc_v4l2_open/*查询设备属性*/

2. VIDIOC_QUERYCAPif (video->streaming->type ==V4L2_BUF_TYPE_VIDEO_CAPTURE)

cap->capabilities =V4L2_CAP_VIDEO_CAPTURE|V4L2_CAP_STREAMING;elsecap->capabilities =V4L2_CAP_VIDEO_OUTPUT|V4L2_CAP_STREAMING;/*枚举设备支持的格式*/

3. VIDIOC_ENUM_FMT

format= &video->streaming->format[fmt->index];/*得到设备当前所使用的 format 与 frame*/

4. VIDIOC_G_FMT

uvc_v4l2_get_formatstruct uvc_format *format = video->streaming->cur_format;struct uvc_frame *frame = video->streaming->cur_frame;/*Check if the hardware supports the requested format.*/

5. VIDIOC_TRY_FMT

uvc_v4l2_try_format/*设置数据，此时并没有真正的设置，而是在启动视频流时将数据发送给设备*/

6. VIDIOC_S_FMT

uvc_v4l2_set_format

uvc_v4l2_try_format

video->streaming->cur_format =format;

video->streaming->cur_frame =frame;/*分配视频缓冲区*/

7. VIDIOC_REQBUFS

uvc_alloc_buffersfor (; nbuffers > 0; --nbuffers) {

mem= vmalloc_32(nbuffers *bufsize);if (mem !=NULL)break;

}/*查询并获取到分配的缓冲区信息*/

8. VIDIOC_QUERYBUF

uvc_query_buffer

__uvc_query_buffer/*映射缓冲区地址到用户空间*/

9. mmap

uvc_v4l2_mmap/*将 V4L2 信息块放入队列*/

10. VIDIOC_QBUF

uvc_queue_buffer

list_add_tail(&buf->queue, &queue->irqqueue);

list_add_tail(&buf->stream, &queue->mainqueue);/*设置设备并启动视频流*/

11. VIDIOC_STREAMON

uvc_video_enable(video,1)/*Commit the streaming parameters.*/uvc_commit_video/*设置 format, frame*/uvc_set_video_ctrl/*启动：Initialize isochronous/bulk URBs and allocate transfer buffers.*/uvc_init_video(video, GFP_KERNEL);

uvc_init_video_isoc/uvc_init_video_bulk

usb_submit_urb/*休眠等待数据*/

12. poll

uvc_v4l2_poll

uvc_queue_poll

poll_wait(file,&buf->wait, wait);/*取出信息块*/

13. VIDIOC_DQBUF

uvc_dequeue_buffer

list_del(&buf->stream);/*关闭视频流*/

14. VIDIOC_STREAMOFF

uvc_video_enable(video,0);

usb_kill_urb(urb);

usb_free_urb(urb);

驱动分析，首先找到 UVC 驱动的入口点：struct uvc_driver uvc_driver ={

.driver={

.name= "uvcvideo",

.probe=uvc_probe,

.disconnect=uvc_disconnect,

.suspend=uvc_suspend,

.resume=uvc_resume,

.reset_resume=uvc_reset_resume,

.id_table=uvc_ids,

.supports_autosuspend= 1,

},

};

usb_register(&uvc_driver.driver);