Man page 9 : struct_ieee80211_ops

struct_ieee80211_ops - callbacks from mac80211 to the driver

tx
    Handler that 802.11 module calls for each transmitted frame. skb contains the buffer starting from the IEEE 802.11 header. The low-level driver should send the frame out based on configuration in the TX control data. This handler should, preferably, never fail and stop queues appropriately. Must be atomic.

start
    Called before the first netdevice attached to the hardware is enabled. This should turn on the hardware and must turn on frame reception (for possibly enabled monitor interfaces.) Returns negative error codes, these may be seen in userspace, or zero. When the device is started it should not have a MAC address to avoid acknowledging frames before a non-monitor device is added. Must be implemented and can sleep.

stop
    Called after last netdevice attached to the hardware is disabled. This should turn off the hardware (at least it must turn off frame reception.) May be called right after add_interface if that rejects an interface. If you added any work onto the mac80211 workqueue you should ensure to cancel it on this callback. Must be implemented and can sleep.

suspend
    Suspend the device; mac80211 itself will quiesce before and stop transmitting and doing any other configuration, and then ask the device to suspend. This is only invoked when WoWLAN is configured, otherwise the device is deconfigured completely and reconfigured at resume time. The driver may also impose special conditions under which it wants to use the « normal » suspend (deconfigure), say if it only supports WoWLAN when the device is associated. In this case, it must return 1 from this function.

resume
    If WoWLAN was configured, this indicates that mac80211 is now resuming its operation, after this the device must be fully functional again. If this returns an error, the only way out is to also unregister the device. If it returns 1, then mac80211 will also go through the regular complete restart on resume.

set_wakeup
    Enable or disable wakeup when WoWLAN configuration is modified. The reason is that device_set_wakeup_enable is supposed to be called when the configuration changes, not only in suspend.

add_interface
    Called when a netdevice attached to the hardware is enabled. Because it is not called for monitor mode devices, start and stop must be implemented. The driver should perform any initialization it needs before the device can be enabled. The initial configuration for the interface is given in the conf parameter. The callback may refuse to add an interface by returning a negative error code (which will be seen in userspace.) Must be implemented and can sleep.

change_interface
    Called when a netdevice changes type. This callback is optional, but only if it is supported can interface types be switched while the interface is UP. The callback may sleep. Note that while an interface is being switched, it will not be found by the interface iteration callbacks.

remove_interface
    Notifies a driver that an interface is going down. The stop callback is called after this if it is the last interface and no monitor interfaces are present. When all interfaces are removed, the MAC address in the hardware must be cleared so the device no longer acknowledges packets, the mac_addr member of the conf structure is, however, set to the MAC address of the device going away. Hence, this callback must be implemented. It can sleep.

config
    Handler for configuration requests. IEEE 802.11 code calls this function to change hardware configuration, e.g., channel. This function should never fail but returns a negative error code if it does. The callback can sleep.

bss_info_changed
    Handler for configuration requests related to BSS parameters that may vary during BSSAqs lifespan, and may affect low level driver (e.g. assoc/disassoc status, erp parameters). This function should not be used if no BSS has been set, unless for association indication. The changed parameter indicates which of the bss parameters has changed when a call is made. The callback can sleep.

start_ap
    Start operation on the AP interface, this is called after all the information in bss_conf is set and beacon can be retrieved. A channel context is bound before this is called. Note that if the driver uses software scan or ROC, this (and stop_ap) isnAqt called when the AP is just « paused » for scanning/ROC, which is indicated by the beacon being disabled/enabled via bss_info_changed.

stop_ap
    Stop operation on the AP interface.

prepare_multicast
    Prepare for multicast filter configuration. This callback is optional, and its return value is passed to configure_filter. This callback must be atomic.

configure_filter
    Configure the deviceAqs RX filter. See the section « Frame filtering » for more information. This callback must be implemented and can sleep.

set_multicast_list
    Configure the deviceAqs interface specific RX multicast filter. This callback is optional. This callback must be atomic.

set_tim
    Set TIM bit. mac80211 calls this function when a TIM bit must be set or cleared for a given STA. Must be atomic.

set_key
    See the section « Hardware crypto acceleration » This callback is only called between add_interface and remove_interface calls, i.e. while the given virtual interface is enabled. Returns a negative error code if the key canAqt be added. The callback can sleep.

update_tkip_key
    See the section « Hardware crypto acceleration » This callback will be called in the context of Rx. Called for drivers which set IEEE80211_KEY_FLAG_TKIP_REQ_RX_P1_KEY. The callback must be atomic.

set_rekey_data
    If the device supports GTK rekeying, for example while the host is suspended, it can assign this callback to retrieve the data necessary to do GTK rekeying, this is the KEK, KCK and replay counter. After rekeying was done it should (for example during resume) notify userspace of the new replay counter using ieee80211_gtk_rekey_notify.

set_default_unicast_key
    Set the default (unicast) key index, useful for WEP when the device sends data packets autonomously, e.g. for ARP offloading. The index can be 0-3, or -1 for unsetting it.

hw_scan
    Ask the hardware to service the scan request, no need to start the scan state machine in stack. The scan must honour the channel configuration done by the regulatory agent in the wiphyAqs registered bands. The hardware (or the driver) needs to make sure that power save is disabled. The req ie/ie_len members are rewritten by mac80211 to contain the entire IEs after the SSID, so that drivers need not look at these at all but just send them after the SSID -- mac80211 includes the (extended) supported rates and HT information (where applicable). When the scan finishes, ieee80211_scan_completed must be called; note that it also must be called when the scan cannot finish due to any error unless this callback returned a negative error code. The callback can sleep.

cancel_hw_scan
    Ask the low-level tp cancel the active hw scan. The driver should ask the hardware to cancel the scan (if possible), but the scan will be completed only after the driver will call ieee80211_scan_completed. This callback is needed for wowlan, to prevent enqueueing a new scan_work after the low-level driver was already suspended. The callback can sleep.

sched_scan_start
    Ask the hardware to start scanning repeatedly at specific intervals. The driver must call the ieee80211_sched_scan_results function whenever it finds results. This process will continue until sched_scan_stop is called.

sched_scan_stop
    Tell the hardware to stop an ongoing scheduled scan.

sw_scan_start
    Notifier function that is called just before a software scan is started. Can be NULL, if the driver doesnAqt need this notification. The callback can sleep.

sw_scan_complete
    Notifier function that is called just after a software scan finished. Can be NULL, if the driver doesnAqt need this notification. The callback can sleep.

get_stats
    Return low-level statistics. Returns zero if statistics are available. The callback can sleep.

get_tkip_seq
    If your device implements TKIP encryption in hardware this callback should be provided to read the TKIP transmit IVs (both IV32 and IV16) for the given key from hardware. The callback must be atomic.

set_frag_threshold
    Configuration of fragmentation threshold. Assign this if the device does fragmentation by itself; if this callback is implemented then the stack will not do fragmentation. The callback can sleep.

set_rts_threshold
    Configuration of RTS threshold (if device needs it) The callback can sleep.

sta_add
    Notifies low level driver about addition of an associated station, AP, IBSS/WDS/mesh peer etc. This callback can sleep.

sta_remove
    Notifies low level driver about removal of an associated station, AP, IBSS/WDS/mesh peer etc. This callback can sleep.

sta_add_debugfs
    Drivers can use this callback to add debugfs files when a station is added to mac80211Aqs station list. This callback and sta_remove_debugfs should be within a CONFIG_MAC80211_DEBUGFS conditional. This callback can sleep.

sta_remove_debugfs
    Remove the debugfs files which were added using sta_add_debugfs. This callback can sleep.

sta_notify
    Notifies low level driver about power state transition of an associated station, AP, IBSS/WDS/mesh peer etc. For a VIF operating in AP mode, this callback will not be called when the flag IEEE80211_HW_AP_LINK_PS is set. Must be atomic.

sta_state
    Notifies low level driver about state transition of a station (which can be the AP, a client, IBSS/WDS/mesh peer etc.) This callback is mutually exclusive with sta_add/sta_remove. It must not fail for down transitions but may fail for transitions up the list of states. The callback can sleep.

sta_rc_update
    Notifies the driver of changes to the bitrates that can be used to transmit to the station. The changes are advertised with bits from enum ieee80211_rate_control_changed and the values are reflected in the station data. This callback should only be used when the driver uses hardware rate control (IEEE80211_HW_HAS_RATE_CONTROL) since otherwise the rate control algorithm is notified directly. Must be atomic.

conf_tx
    Configure TX queue parameters (EDCF (aifs, cw_min, cw_max), bursting) for a hardware TX queue. Returns a negative error code on failure. The callback can sleep.

get_tsf
    Get the current TSF timer value from firmware/hardware. Currently, this is only used for IBSS mode BSSID merging and debugging. Is not a required function. The callback can sleep.

set_tsf
    Set the TSF timer to the specified value in the firmware/hardware. Currently, this is only used for IBSS mode debugging. Is not a required function. The callback can sleep.

reset_tsf
    Reset the TSF timer and allow firmware/hardware to synchronize with other STAs in the IBSS. This is only used in IBSS mode. This function is optional if the firmware/hardware takes full care of TSF synchronization. The callback can sleep.

tx_last_beacon
    Determine whether the last IBSS beacon was sent by us. This is needed only for IBSS mode and the result of this function is used to determine whether to reply to Probe Requests. Returns non-zero if this device sent the last beacon. The callback can sleep.

ampdu_action
    Perform a certain A-MPDU action The RA/TID combination determines the destination and TID we want the ampdu action to be performed for. The action is defined through ieee80211_ampdu_mlme_action. Starting sequence number (ssn) is the first frame we expect to perform the action on. Notice that TX/RX_STOP can pass NULL for this parameter. The buf_size parameter is only valid when the action is set to IEEE80211_AMPDU_TX_OPERATIONAL and indicates the peerAqs reorder buffer size (number of subframes) for this session -- the driver may neither send aggregates containing more subframes than this nor send aggregates in a way that lost frames would exceed the buffer size. If just limiting the aggregate size, this would be

get_survey
    Return per-channel survey information

rfkill_poll
    Poll rfkill hardware state. If you need this, you also need to set wiphy->rfkill_poll to true before registration, and need to call wiphy_rfkill_set_hw_state in the callback. The callback can sleep.

set_coverage_class
    Set slot time for given coverage class as specified in IEEE 802.11-2007 section 17.3.8.6 and modify ACK timeout accordingly. This callback is not required and may sleep.

testmode_cmd
    Implement a cfg80211 test mode command. The callback can sleep.

testmode_dump
    Implement a cfg80211 test mode dump. The callback can sleep.

flush
    Flush all pending frames from the hardware queue, making sure that the hardware queues are empty. The queues parameter is a bitmap of queues to flush, which is useful if different virtual interfaces use different hardware queues; it may also indicate all queues. If the parameter drop is set to true, pending frames may be dropped. The callback can sleep.

channel_switch
    Drivers that need (or want) to offload the channel switch operation for CSAs received from the AP may implement this callback. They must then call ieee80211_chswitch_done to indicate completion of the channel switch.

napi_poll
    Poll Rx queue for incoming data frames.

set_antenna
    Set antenna configuration (tx_ant, rx_ant) on the device. Parameters are bitmaps of allowed antennas to use for TX/RX. Drivers may reject TX/RX mask combinations they cannot support by returning -EINVAL (also see nl80211.h NL80211_ATTR_WIPHY_ANTENNA_TX).

get_antenna
    Get current antenna configuration from device (tx_ant, rx_ant).

remain_on_channel
    Starts an off-channel period on the given channel, must call back to ieee80211_ready_on_channel when on that channel. Note that normal channel traffic is not stopped as this is intended for hw offload. Frames to transmit on the off-channel channel are transmitted normally except for the IEEE80211_TX_CTL_TX_OFFCHAN flag. When the duration (which will always be non-zero) expires, the driver must call ieee80211_remain_on_channel_expired. Note that this callback may be called while the device is in IDLE and must be accepted in this case. This callback may sleep.

cancel_remain_on_channel
    Requests that an ongoing off-channel period is aborted before it expires. This callback may sleep.

set_ringparam
    Set tx and rx ring sizes.

get_ringparam
    Get tx and rx ring current and maximum sizes.

tx_frames_pending
    Check if there is any pending frame in the hardware queues before entering power save.

set_bitrate_mask
    Set a mask of rates to be used for rate control selection when transmitting a frame. Currently only legacy rates are handled. The callback can sleep.

rssi_callback
    Notify driver when the average RSSI goes above/below thresholds that were registered previously. The callback can sleep.

allow_buffered_frames
    Prepare device to allow the given number of frames to go out to the given station. The frames will be sent by mac80211 via the usual TX path after this call. The TX information for frames released will also have the IEEE80211_TX_CTL_NO_PS_BUFFER flag set and the last one will also have IEEE80211_TX_STATUS_EOSP set. In case frames from multiple TIDs are released and the driver might reorder them between the TIDs, it must set the IEEE80211_TX_STATUS_EOSP flag on the last frame and clear it on all others and also handle the EOSP bit in the QoS header correctly. Alternatively, it can also call the ieee80211_sta_eosp function. The tids parameter is a bitmap and tells the driver which TIDs the frames will be on; it will at most have two bits set. This callback must be atomic.

release_buffered_frames
    Release buffered frames according to the given parameters. In the case where the driver buffers some frames for sleeping stations mac80211 will use this callback to tell the driver to release some frames, either for PS-poll or uAPSD. Note that if the more_data paramter is false the driver must check if there are more frames on the given TIDs, and if there are more than the frames being released then it must still set the more-data bit in the frame. If the more_data parameter is true, then of course the more-data bit must always be set. The tids parameter tells the driver which TIDs to release frames from, for PS-poll it will always have only a single bit set. In the case this is used for a PS-poll initiated release, the num_frames parameter will always be 1 so code can be shared. In this case the driver must also set IEEE80211_TX_STATUS_EOSP flag on the TX status (and must report TX status) so that the PS-poll period is properly ended. This is used to avoid sending multiple responses for a retried PS-poll frame. In the case this is used for uAPSD, the num_frames parameter may be bigger than one, but the driver may send fewer frames (it must send at least one, however). In this case it is also responsible for setting the EOSP flag in the QoS header of the frames. Also, when the service period ends, the driver must set IEEE80211_TX_STATUS_EOSP on the last frame in the SP. Alternatively, it may call the function ieee80211_sta_eosp to inform mac80211 of the end of the SP. This callback must be atomic.

get_et_sset_count
    Ethtool API to get string-set count.

get_et_stats
    Ethtool API to get a set of u64 stats.

get_et_strings
    Ethtool API to get a set of strings to describe stats and perhaps other supported types of ethtool data-sets.

get_rssi
    Get current signal strength in dBm, the function is optional and can sleep.

mgd_prepare_tx
    Prepare for transmitting a management frame for association before associated. In multi-channel scenarios, a virtual interface is bound to a channel before it is associated, but as it isnAqt associated yet it need not necessarily be given airtime, in particular since any transmission to a P2P GO needs to be synchronized against the GOAqs powersave state. mac80211 will call this function before transmitting a management frame prior to having successfully associated to allow the driver to give it channel time for the transmission, to get a response and to be able to synchronize with the GO. The callback will be called before each transmission and upon return mac80211 will transmit the frame right away. The callback is optional and can (should!) sleep.

add_chanctx
    Notifies device driver about new channel context creation.

remove_chanctx
    Notifies device driver about channel context destruction.

change_chanctx
    Notifies device driver about channel context changes that may happen when combining different virtual interfaces on the same channel context with different settings

assign_vif_chanctx
    Notifies device driver about channel context being bound to vif. Possible use is for hw queue remapping.

unassign_vif_chanctx
    Notifies device driver about channel context being unbound from vif.

restart_complete
    Called after a call to ieee80211_restart_hw, when the reconfiguration has completed. This can help the driver implement the reconfiguration step. Also called when reconfiguring because the driverAqs resume function returned 1, as this is just like an « inline » hardware restart. This callback may sleep.

ipv6_addr_change
    IPv6 address assignment on the given interface changed. Currently, this is only called for managed or P2P client interfaces. This callback is optional; it must not sleep.

This structure contains various callbacks that the driver may handle or, in some cases, must handle, for example to configure the hardware to a new channel or to transmit a frame.

- TX: 1.....7 - RX: 2....7 (lost frame #1) - TX: 8..1... which is invalid since #1 was now re-transmitted well past the buffer size of 8. Correct ways to retransmit #1 would be: - TX: 1 or 18 or 81 Even « 189 » would be wrong since 1 could be lost again.

Returns a negative error code on failure. The callback can sleep.

Johannes Berg <>
    Author.