From c99445b14054e0c4ed4715df1dad1fc608cbab46 Mon Sep 17 00:00:00 2001 From: Kalle Valo Date: Thu, 14 Jan 2010 13:09:21 +0200 Subject: mac80211: improve powersave documentation There has been some confusion how drivers should implement powersave support. Improve the documentation a bit to make it more clear what drivers need to do. Also mention about U-APSD. Signed-off-by: Kalle Valo Signed-off-by: John W. Linville --- include/net/mac80211.h | 75 ++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 54 insertions(+), 21 deletions(-) (limited to 'include/net/mac80211.h') diff --git a/include/net/mac80211.h b/include/net/mac80211.h index bbfa4750092e..c90047de4428 100644 --- a/include/net/mac80211.h +++ b/include/net/mac80211.h @@ -569,7 +569,13 @@ struct ieee80211_rx_status { * @IEEE80211_CONF_MONITOR: there's a monitor interface present -- use this * to determine for example whether to calculate timestamps for packets * or not, do not use instead of filter flags! - * @IEEE80211_CONF_PS: Enable 802.11 power save mode (managed mode only) + * @IEEE80211_CONF_PS: Enable 802.11 power save mode (managed mode only). + * This is the power save mode defined by IEEE 802.11-2007 section 11.2, + * meaning that the hardware still wakes up for beacons, is able to + * transmit frames and receive the possible acknowledgment frames. + * Not to be confused with hardware specific wakeup/sleep states, + * driver is responsible for that. See the section "Powersave support" + * for more. * @IEEE80211_CONF_IDLE: The device is running, but idle; if the flag is set * the driver should be prepared to handle configuration requests but * may turn the device off as much as possible. Typically, this flag will @@ -1138,18 +1144,24 @@ ieee80211_get_alt_retry_rate(const struct ieee80211_hw *hw, * * mac80211 has support for various powersave implementations. * - * First, it can support hardware that handles all powersaving by - * itself, such hardware should simply set the %IEEE80211_HW_SUPPORTS_PS - * hardware flag. In that case, it will be told about the desired - * powersave mode depending on the association status, and the driver - * must take care of sending nullfunc frames when necessary, i.e. when - * entering and leaving powersave mode. The driver is required to look at - * the AID in beacons and signal to the AP that it woke up when it finds - * traffic directed to it. This mode supports dynamic PS by simply - * enabling/disabling PS. - * - * Additionally, such hardware may set the %IEEE80211_HW_SUPPORTS_DYNAMIC_PS - * flag to indicate that it can support dynamic PS mode itself (see below). + * First, it can support hardware that handles all powersaving by itself, + * such hardware should simply set the %IEEE80211_HW_SUPPORTS_PS hardware + * flag. In that case, it will be told about the desired powersave mode + * with the %IEEE80211_CONF_PS flag depending on the association status. + * The hardware must take care of sending nullfunc frames when necessary, + * i.e. when entering and leaving powersave mode. The hardware is required + * to look at the AID in beacons and signal to the AP that it woke up when + * it finds traffic directed to it. + * + * %IEEE80211_CONF_PS flag enabled means that the powersave mode defined in + * IEEE 802.11-2007 section 11.2 is enabled. This is not to be confused + * with hardware wakeup and sleep states. Driver is responsible for waking + * up the hardware before issueing commands to the hardware and putting it + * back to sleep at approriate times. + * + * When PS is enabled, hardware needs to wakeup for beacons and receive the + * buffered multicast/broadcast frames after the beacon. Also it must be + * possible to send frames and receive the acknowledment frame. * * Other hardware designs cannot send nullfunc frames by themselves and also * need software support for parsing the TIM bitmap. This is also supported @@ -1157,14 +1169,35 @@ ieee80211_get_alt_retry_rate(const struct ieee80211_hw *hw, * %IEEE80211_HW_PS_NULLFUNC_STACK flags. The hardware is of course still * required to pass up beacons. The hardware is still required to handle * waking up for multicast traffic; if it cannot the driver must handle that - * as best as it can, mac80211 is too slow. - * - * Dynamic powersave mode is an extension to normal powersave mode in which - * the hardware stays awake for a user-specified period of time after sending - * a frame so that reply frames need not be buffered and therefore delayed - * to the next wakeup. This can either be supported by hardware, in which case - * the driver needs to look at the @dynamic_ps_timeout hardware configuration - * value, or by the stack if all nullfunc handling is in the stack. + * as best as it can, mac80211 is too slow to do that. + * + * Dynamic powersave is an extension to normal powersave in which the + * hardware stays awake for a user-specified period of time after sending a + * frame so that reply frames need not be buffered and therefore delayed to + * the next wakeup. It's compromise of getting good enough latency when + * there's data traffic and still saving significantly power in idle + * periods. + * + * Dynamic powersave is supported by simply mac80211 enabling and disabling + * PS based on traffic. Driver needs to only set %IEEE80211_HW_SUPPORTS_PS + * flag and mac80211 will handle everything automatically. Additionally, + * hardware having support for the dynamic PS feature may set the + * %IEEE80211_HW_SUPPORTS_DYNAMIC_PS flag to indicate that it can support + * dynamic PS mode itself. The driver needs to look at the + * @dynamic_ps_timeout hardware configuration value and use it that value + * whenever %IEEE80211_CONF_PS is set. In this case mac80211 will disable + * dynamic PS feature in stack and will just keep %IEEE80211_CONF_PS + * enabled whenever user has enabled powersave. + * + * Driver informs U-APSD client support by enabling + * %IEEE80211_HW_SUPPORTS_UAPSD flag. The mode is configured through the + * uapsd paramater in conf_tx() operation. Hardware needs to send the QoS + * Nullfunc frames and stay awake until the service period has ended. To + * utilize U-APSD, dynamic powersave is disabled for voip AC and all frames + * from that AC are transmitted with powersave enabled. + * + * Note: U-APSD client mode is not yet supported with + * %IEEE80211_HW_PS_NULLFUNC_STACK. */ /** -- cgit v1.2.2