从cimutils到内核-(3)VIDIOC_QBUF(buffer进入视频缓存队列)

应用层：

 

case IO_METHOD_MMAP:

for (i=0; i

struct v4l2_buffer buf;

CLEAR(buf);

buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

buf.memory = V4L2_MEMORY_MMAP;

buf.index = i; //i = 0,1

if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))

errno_exit("VIDIOC_QBUF");

}

type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))

errno_exit("VIDIOC_STREAMON");

break;

 

 

------------------------------------------------------------------------------------------------------------------------------------------------------------

 

内核:

 

(1)

drivers/media/v4l2-core/v4l2-ioctl.c

IOCTL_INFO_FNC(VIDIOC_QBUF, v4l_qbuf, v4l_print_buffer, INFO_FL_QUEUE)

 

static int v4l_qbuf(const struct v4l2_ioctl_ops *ops,

struct file *file, void *fh, void *arg)

{

struct v4l2_buffer *p = arg;

int ret = check_fmt(file, p->type);

return ret ? ret : ops->vidioc_qbuf(file, fh, p); //strtuct file对应 应用层打开的/dev/vedio0 的文件描述符fd

}

 

(2)

drivers/media/platform/soc_camera/soc_camera.c

static int soc_camera_qbuf(struct file *file, void *priv,

struct v4l2_buffer *p)

{

struct soc_camera_device *icd = file->private_data;

struct soc_camera_host *ici = to_soc_camera_host(icd->parent);

WARN_ON(priv != file->private_data);

if (icd->streamer != file)

return -EBUSY;

if (ici->ops->init_videobuf)

return videobuf_qbuf(&icd->vb_vidq, p);

else

return vb2_qbuf(&icd->vb2_vidq, p);

}

 

int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)

{

/*

* Add to the queued buffers list, a buffer will stay on it until

* dequeued in dqbuf.

*/

list_add_tail(&vb->queued_entry, &q->queued_list);

vb->state = VB2_BUF_STATE_QUEUED; //把buffer[0] 和 buffer[1]加入链表queued_list，一直存在，直到在dqbuf的时候dequeued一个buffer

 

if (q->streaming)

__enqueue_in_driver(vb); //执行完streamon后才进入

 

/* Fill buffer information for the userspace */

__fill_v4l2_buffer(vb, b);

}