如何在linux下，实现ov5640之类的cmos摄像头的驱动？
使用5.1系统的kernel，rk3288-reload开发板，在linux下开发使用内核自带的摄像头驱动，写了一个测试程序，但是把申请的缓冲区放入队列时失败了，查找了原因，是在：
1. for (i = 0; i < NB_BUFFER; i++) {
2. memset(&tV4l2Buf, 0, sizeof(struct v4l2_buffer));
3. tV4l2Buf.index = i;
4. tV4l2Buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
5. tV4l2Buf.memory = V4L2_MEMORY_MMAP;
6. tV4l2Buf.flags = 0;
7. iRet = ioctl(v4l2_fd, VIDIOC_QUERYBUF, &tV4l2Buf);
8. if (iRet < 0) {
9. DWrite("Unable to query buffer.\n");
10. goto end;
11. }
12.
13. printf("length: 0x%x offset: 0x%x\n", tV4l2Buf.length, tV4l2Buf.m.offset);
14.
15. pucVideoBuf = (unsigned char *)mmap(0, /* start anywhere */
16. tV4l2Buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, v4l2_fd,
17. tV4l2Buf.m.offset);
18. if (pucVideoBuf == MAP_FAILED) {
19. DWrite("Unable to map buffer\n");
20. goto end;
21. }
22. printf("length: 0x%x offset: 0x%x\n", tV4l2Buf.length, tV4l2Buf.m.offset);
23. 打印出来的结果是：
24. length: 0xeb000 offset: 0x0
25. length: 0xeb000 offset: 0xeb000
26. length: 0xeb000 offset: 0x1d6000
27. length: 0xeb000 offset: 0x2c1000
随后通过映射的地址加入缓冲队列 调用
ioctl(v4l2_fd, VIDIOC_QBUF, &tV4l2Buf);
返回-1失败提示通过 fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno));
打印 error 22, Invalid argument” 问题解决了吗
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