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mac80211: improve powersave documentation

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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 <kalle.valo@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Kalle Valo 2010-01-14 13:09:21 +02:00 committed by John W. Linville
parent 9d173fc5df
commit c99445b140
1 changed files with 52 additions and 19 deletions
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71
include/net/mac80211.h
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@ -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.
* 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.
*
* Additionally, such hardware may set the %IEEE80211_HW_SUPPORTS_DYNAMIC_PS
* flag to indicate that it can support dynamic PS mode itself (see below).
* %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.
* as best as it can, mac80211 is too slow to do that.
*
* 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.
* 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.
*/
/**