static inline int __vringh_need_notify()

in vringh.c [481:526]

• 35 lines of code
• 5 McCabe index (conditional complexity)

static inline int __vringh_need_notify(struct vringh *vrh,
				       int (*getu16)(const struct vringh *vrh,
						     u16 *val,
						     const __virtio16 *p))
{
	bool notify;
	u16 used_event;
	int err;

	/* Flush out used index update. This is paired with the
	 * barrier that the Guest executes when enabling
	 * interrupts. */
	virtio_mb(vrh->weak_barriers);

	/* Old-style, without event indices. */
	if (!vrh->event_indices) {
		u16 flags;
		err = getu16(vrh, &flags, &vrh->vring.avail->flags);
		if (err) {
			vringh_bad("Failed to get flags at %p",
				   &vrh->vring.avail->flags);
			return err;
		}
		return (!(flags & VRING_AVAIL_F_NO_INTERRUPT));
	}

	/* Modern: we know when other side wants to know. */
	err = getu16(vrh, &used_event, &vring_used_event(&vrh->vring));
	if (err) {
		vringh_bad("Failed to get used event idx at %p",
			   &vring_used_event(&vrh->vring));
		return err;
	}

	/* Just in case we added so many that we wrap. */
	if (unlikely(vrh->completed > 0xffff))
		notify = true;
	else
		notify = vring_need_event(used_event,
					  vrh->last_used_idx + vrh->completed,
					  vrh->last_used_idx);

	vrh->last_used_idx += vrh->completed;
	vrh->completed = 0;
	return notify;
}