mac80211 TID selection?

Why is it that mac80211 determines the tid as

tid = skb->priority & IEEE80211_QOS_CTL_TAG1D_MASK;

?

Since the latter value is 0x7, that can only fill TIDs 0 through 7
instead of o through 15, shouldn't we be able to use the full space
somehow? Or if not, shouldn't we reduce tid_to_tx_q to have just 8
entries instead of 16?

johannes