• Johannes Berg's avatar
    mac80211: async station powersave handling · af818581
    Johannes Berg authored
    Some devices require that all frames to a station
    are flushed when that station goes into powersave
    mode before being able to send frames to that
    station again when it wakes up or polls -- all in
    order to avoid reordering and too many or too few
    frames being sent to the station when it polls.
    Normally, this is the case unless the station
    goes to sleep and wakes up very quickly again.
    But in that case, frames for it may be pending
    on the hardware queues, and thus races could
    happen in the case of multiple hardware queues
    used for QoS/WMM. Normally this isn't a problem,
    but with the iwlwifi mechanism we need to make
    sure the race doesn't happen.
    This makes mac80211 able to cope with the race
    with driver help by a new WLAN_STA_PS_DRIVER
    per-station flag that can be controlled by the
    driver and tells mac80211 whether it can transmit
    frames or not. This flag must be set according to
    very specific rules outlined in the documentation
    for the function that controls it.
    When we buffer new frames for the station, we
    normally set the TIM bit right away, but while
    the driver has blocked transmission to that sta
    we need to avoid that as well since we cannot
    respond to the station if it wakes up due to the
    TIM bit. Once the driver unblocks, we can set
    the TIM bit.
    Similarly, when the station just wakes up, we
    need to wait until all other frames are flushed
    before we can transmit frames to that station,
    so the same applies here, we need to wait for
    the driver to give the OK.
    Signed-off-by: default avatarJohannes Berg <johannes@sipsolutions.net>
    Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
mac80211.h 87 KB