Chapter 8. Beacon filter support

Table of Contents

ieee80211_beacon_loss — inform hardware does not receive beacons

Some hardware have beacon filter support to reduce host cpu wakeups which will reduce system power consumption. It usuallly works so that the firmware creates a checksum of the beacon but omits all constantly changing elements (TSF, TIM etc). Whenever the checksum changes the beacon is forwarded to the host, otherwise it will be just dropped. That way the host will only receive beacons where some relevant information (for example ERP protection or WMM settings) have changed.

Beacon filter support is informed with IEEE80211_HW_BEACON_FILTER flag. The driver needs to enable beacon filter support whenever power save is enabled, that is IEEE80211_CONF_PS is set. When power save is enabled, the stack will not check for beacon miss at all and the driver needs to notify about complete loss of beacons with ieee80211_beacon_loss.