通达信接口官网-v4l2 poll驱动唤醒应用等待队列_ 股票程序化软件自动交易接口

int sync_wait(int fd, int timeout) { struct pollfd fds; int ret; if (fd < 0) { errno = EINVAL; return -1; } fds.fd = fd; fds.events = POLLIN; do { ret = poll(&fds, 1, timeout); if (ret > 0) { if (fds.revents & (POLLERR | POLLNVAL)) { errno = EINVAL; return -1; } return 0; } else if (ret == 0) { errno = ETIME; return -1; } } while (ret == -1 && (errno == EINTR || errno == EAGAIN)); return ret; }

poll调用到驱动实现的字符设备poll接口

static const struct v4l2_file_operations video_file_ops = {
	.owner = THIS_MODULE,
	.unlocked_ioctl = video_ioctl2,
	.open = video_open,
	.release = video_release,
	.poll = vb2_fop_poll,
	.mmap = vb2_fop_mmap,
	.read = vb2_fop_read,
};

vb2_fop_poll
--vb2_poll
----vb2_core_poll
------poll_wait

	if (list_empty(&q->done_list)) {
		/*
		 * If the last buffer was dequeued from a capture queue,
		 * return immediately. DQBUF will return -EPIPE.
		 */
		if (q->last_buffer_dequeued)
			return POLLIN | POLLRDNORM;

		poll_wait(file, &q->done_wq, wait);
	}

等待q->done_wq唤醒

vb2_buffer_done

--
	switch (state) {
	case VB2_BUF_STATE_QUEUED:
		return;
	case VB2_BUF_STATE_REQUEUEING:
		if (q->start_streaming_called)
			__enqueue_in_driver(vb);
		return;
	default:
		/* Inform any processes that may be waiting for buffers */
		wake_up(&q->done_wq);
		break;
	}

--

实现的驱动会调用vb2_buffer_done，唤醒q->done_wq的等待队列，此时应用即可DQBUF。

文章为作者独立观点，不代表股票程序化软件自动交易接口观点