ssize_t ptp_read()

in ptp_chardev.c [443:505]

• 47 lines of code
• 11 McCabe index (conditional complexity)

ssize_t ptp_read(struct posix_clock *pc,
		 uint rdflags, char __user *buf, size_t cnt)
{
	struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
	struct timestamp_event_queue *queue = &ptp->tsevq;
	struct ptp_extts_event *event;
	unsigned long flags;
	size_t qcnt, i;
	int result;

	if (cnt % sizeof(struct ptp_extts_event) != 0)
		return -EINVAL;

	if (cnt > EXTTS_BUFSIZE)
		cnt = EXTTS_BUFSIZE;

	cnt = cnt / sizeof(struct ptp_extts_event);

	if (mutex_lock_interruptible(&ptp->tsevq_mux))
		return -ERESTARTSYS;

	if (wait_event_interruptible(ptp->tsev_wq,
				     ptp->defunct || queue_cnt(queue))) {
		mutex_unlock(&ptp->tsevq_mux);
		return -ERESTARTSYS;
	}

	if (ptp->defunct) {
		mutex_unlock(&ptp->tsevq_mux);
		return -ENODEV;
	}

	event = kmalloc(EXTTS_BUFSIZE, GFP_KERNEL);
	if (!event) {
		mutex_unlock(&ptp->tsevq_mux);
		return -ENOMEM;
	}

	spin_lock_irqsave(&queue->lock, flags);

	qcnt = queue_cnt(queue);

	if (cnt > qcnt)
		cnt = qcnt;

	for (i = 0; i < cnt; i++) {
		event[i] = queue->buf[queue->head];
		queue->head = (queue->head + 1) % PTP_MAX_TIMESTAMPS;
	}

	spin_unlock_irqrestore(&queue->lock, flags);

	cnt = cnt * sizeof(struct ptp_extts_event);

	mutex_unlock(&ptp->tsevq_mux);

	result = cnt;
	if (copy_to_user(buf, event, cnt))
		result = -EFAULT;

	kfree(event);
	return result;
}