static ssize_t uio_read()

in uio.c [565:618]

• 45 lines of code
• 9 McCabe index (conditional complexity)

static ssize_t uio_read(struct file *filep, char __user *buf,
			size_t count, loff_t *ppos)
{
	struct uio_listener *listener = filep->private_data;
	struct uio_device *idev = listener->dev;
	DECLARE_WAITQUEUE(wait, current);
	ssize_t retval = 0;
	s32 event_count;

	if (count != sizeof(s32))
		return -EINVAL;

	add_wait_queue(&idev->wait, &wait);

	do {
		mutex_lock(&idev->info_lock);
		if (!idev->info || !idev->info->irq) {
			retval = -EIO;
			mutex_unlock(&idev->info_lock);
			break;
		}
		mutex_unlock(&idev->info_lock);

		set_current_state(TASK_INTERRUPTIBLE);

		event_count = atomic_read(&idev->event);
		if (event_count != listener->event_count) {
			__set_current_state(TASK_RUNNING);
			if (copy_to_user(buf, &event_count, count))
				retval = -EFAULT;
			else {
				listener->event_count = event_count;
				retval = count;
			}
			break;
		}

		if (filep->f_flags & O_NONBLOCK) {
			retval = -EAGAIN;
			break;
		}

		if (signal_pending(current)) {
			retval = -ERESTARTSYS;
			break;
		}
		schedule();
	} while (1);

	__set_current_state(TASK_RUNNING);
	remove_wait_queue(&idev->wait, &wait);

	return retval;
}