Tracing Association code

Hi All, I am tracing the association code in linux-wireless. I understand that association request has to be triggered from station side (userspace-wpa_supplicant) and has to be sent to the AP (userspace-hostapd). In the process of tracing, I found the function ieee80211_assoc(...) in net/mac80211/cfg.c and also I found that a timer is scheduled to execute the timer function. My Questions are 1. Who is initiating the timer function, my guess is it should be the driver & How ? 2. On the AP side how is the association request taken from driver -> mac80211 -> hostapd. Appreciate your help. Thanks, Prabhu