cfg80211_chandef_dfs_usable(9)

💅 cfg80211_chandef_dfs_usable(9)

okay so bestie, welcome to the Kernel API Manual ✨ — this one's a little function with a big job and honestly? it's giving gatekeeper energy. let's get into it 🎀

✨ NAME ✨

cfg80211_chandef_dfs_usable — checks if chandef is DFS usable and we can/need start CAC on such channel 🦋

like, it's literally the vibe check for whether a channel definition is DFS-usable and whether we can or need to start CAC on that channel, iykyk 💅

🌸 SYNOPSIS 🌸

bool cfg80211_chandef_dfs_usable (struct wiphy *wiphy , const struct
       cfg80211_chan_def *chandef );

returns a bool, takes two pointers, no cap 🫶

👑 ARGUMENTS 👑

wiphy — the wiphy to validate against 🔥 like, this is the thing we're checking everything against, the main character, the reference point
chandef — the channel definition to check 💖 the actual channel sitch you're asking about

⭐ RETURN ⭐

true if all channels available and at least one channel requires CAC (NL80211_DFS_USABLE) 💀✨

so like — all channels gotta be available, and at least one of them has to require CAC. both. together. that's the combo that gets you a true, periodt 👑

careful bestie: it's not true for just anything — the all-channels-available part AND the at-least-one-requires-CAC part both have to be true. that's literally the whole point of the function 🙈

that's part 1, more incoming 🌈

✨ SEE ALSO ✨

okay bestie, so this is the part where the page shows you everyone else in the friend group 💅 and no, I'm not gonna skip any of them, because there are literally like 359 of these and each one is a real cross-reference you might actually need. every single name below is written exactly how it appears, (9) and all — that's just how these are spelled here, don't come for me 🫶

the header itself lives at Kernel file ./include/net/cfg80211.h, and the soft intro pages are Introduction(9) and Device registration(9) — start there if you're brand new, no cap.

🎀 the channel / band / rate besties

enum ieee80211_channel_flags(9), struct ieee80211_channel(9), enum ieee80211_rate_flags(9), enum ieee80211_bss_type(9), enum ieee80211_privacy(9), struct ieee80211_rate(9), struct ieee80211_he_obss_pd(9), struct cfg80211_he_bss_color(9)
struct ieee80211_sta_ht_cap(9), struct ieee80211_sta_vht_cap(9), struct ieee80211_sta_he_cap(9), struct ieee80211_eht_mcs_nss_supp(9), struct ieee80211_sta_eht_cap(9), struct ieee80211_sta_uhr_cap(9), struct ieee80211_sband_iftype_data(9), enum ieee80211_edmg_bw_config(9), struct ieee80211_edmg(9), struct ieee80211_sta_s1g_cap(9), struct ieee80211_supported_band(9)
_ieee80211_set_sband_iftype_data(9), ieee80211_set_sband_iftype_data(9), for_each_sband_iftype_data(9), ieee80211_get_sband_iftype_data(9), ieee80211_get_he_iftype_cap(9), ieee80211_get_he_6ghz_capa(9), ieee80211_get_eht_iftype_cap(9), ieee80211_get_uhr_iftype_cap(9), wiphy_read_of_freq_limits(9)

yes, _ieee80211_set_sband_iftype_data(9) really does have that little underscore in front. it's not a typo, it's just the shy one 🙈

🌸 actions & configuration era

Actions and configuration(9), struct vif_params(9), struct key_params(9), struct cfg80211_chan_def(9), struct cfg80211_tid_cfg(9), struct cfg80211_tid_config(9), struct cfg80211_fils_aad(9), struct cfg80211_set_hw_timestamp(9)

💜 the whole chandef cinematic universe

cfg80211_get_chandef_type(9), cfg80211_chandef_create(9), cfg80211_chandef_identical(9), cfg80211_chandef_is_edmg(9), cfg80211_chandef_is_s1g(9), cfg80211_chandef_compatible(9), nl80211_chan_width_to_mhz(9), cfg80211_chandef_get_width(9), cfg80211_chandef_valid(9), cfg80211_chandef_usable(9), cfg80211_chandef_dfs_required(9), cfg80211_chandef_dfs_cac_time(9), cfg80211_chandef_primary(9), cfg80211_chandef_npca_valid(9), cfg80211_chandef_add_npca(9), cfg80211_chandef_add_dbe(9), nl80211_send_chandef(9), ieee80211_chandef_max_power(9), cfg80211_chandef_s1g_pri_width(9), cfg80211_any_usable_channels(9)

like, that's the family this page belongs to fr fr — you literally saw cfg80211_chandef_usable(9) up in the synopsis and now here's all its siblings 💖

🦋 survey, AP, beacons & friends

enum survey_info_flags(9), struct survey_info(9), struct cfg80211_crypto_settings(9), struct cfg80211_mbssid_config(9), struct cfg80211_mbssid_elems(9), struct cfg80211_rnr_elems(9), struct cfg80211_beacon_data(9), struct cfg80211_acl_data(9), struct cfg80211_fils_discovery(9), struct cfg80211_unsol_bcast_probe_resp(9), struct cfg80211_s1g_short_beacon(9), struct cfg80211_ap_settings(9), struct cfg80211_ap_update(9), struct cfg80211_csa_settings(9), struct cfg80211_color_change_settings(9), struct iface_combination_params(9)

⭐ station, rates & stats

enum station_parameters_apply_mask(9), struct sta_txpwr(9), struct link_station_parameters(9), struct link_station_del_parameters(9), struct cfg80211_ttlm_params(9), struct station_parameters(9), struct station_del_parameters(9), enum cfg80211_station_type(9), cfg80211_check_station_change(9), enum rate_info_flags(9), enum rate_info_bw(9), struct rate_info(9), enum bss_param_flags(9), struct sta_bss_parameters(9), struct cfg80211_txq_stats(9), struct cfg80211_tid_stats(9), struct link_station_info(9), struct station_info(9)

🍓 SAR, monitor, mesh, OCB & txq

struct cfg80211_sar_sub_specs(9), struct cfg80211_sar_specs(9), struct cfg80211_sar_freq_ranges(9), struct cfg80211_sar_capa(9), cfg80211_get_station(9), enum monitor_flags(9), enum mpath_info_flags(9), struct mpath_info(9), enum wiphy_bss_param_flags(9), struct bss_parameters(9), struct mesh_config(9), struct mesh_setup(9), struct ocb_setup(9), struct ieee80211_txq_params(9)

🧚 scanning & BSS list handling (a whole moment)

Scanning and BSS list handling(9), struct cfg80211_ssid(9), struct cfg80211_scan_info(9), struct cfg80211_scan_6ghz_params(9), struct cfg80211_scan_request(9), struct cfg80211_match_set(9), struct cfg80211_sched_scan_plan(9), struct cfg80211_bss_select_adjust(9), struct cfg80211_sched_scan_request(9), enum cfg80211_signal_type(9), struct cfg80211_inform_bss(9), struct cfg80211_bss_ies(9), struct cfg80211_bss(9), ieee80211_bss_get_elem(9), ieee80211_bss_get_ie(9)

🎀 auth, assoc & connect structs

struct cfg80211_auth_request(9), struct cfg80211_assoc_link(9), struct cfg80211_ml_reconf_req(9), enum cfg80211_assoc_req_flags(9), struct cfg80211_assoc_request(9), struct cfg80211_deauth_request(9), struct cfg80211_disassoc_request(9), struct cfg80211_ibss_params(9), struct cfg80211_bss_selection(9), struct cfg80211_connect_params(9), enum cfg80211_connect_params_changed(9), enum wiphy_params_flags(9), struct cfg80211_pmksa(9)

💅 patterns, wowlan, coalesce & qos

struct cfg80211_pkt_pattern(9), struct cfg80211_wowlan_tcp(9), struct cfg80211_wowlan(9), struct cfg80211_coalesce_rules(9), struct cfg80211_coalesce(9), struct cfg80211_wowlan_nd_match(9), struct cfg80211_wowlan_nd_info(9), struct cfg80211_wowlan_wakeup(9), struct cfg80211_gtk_rekey_data(9), struct cfg80211_update_ft_ies_params(9), struct cfg80211_mgmt_tx_params(9), struct cfg80211_dscp_exception(9), struct cfg80211_dscp_range(9), struct cfg80211_qos_map(9)

🔥 NAN (Neighbor Awareness Networking) corner

Neighbor Awareness Networking (NAN)(9), struct cfg80211_nan_band_config(9), struct cfg80211_nan_conf(9), struct cfg80211_nan_channel(9), struct cfg80211_nan_local_sched(9), struct cfg80211_nan_peer_map(9), struct cfg80211_nan_peer_sched(9), enum cfg80211_nan_conf_changes(9), struct cfg80211_nan_func_filter(9), struct cfg80211_nan_func(9)

🫶 PMK, external auth, FTM/PMSR & OWE

struct cfg80211_pmk_conf(9), struct cfg80211_external_auth_params(9), struct cfg80211_ftm_responder_stats(9), struct cfg80211_pmsr_ftm_result(9), struct cfg80211_pmsr_result(9), struct cfg80211_pmsr_ftm_request_peer(9), struct cfg80211_pmsr_request_peer(9), struct cfg80211_pmsr_request(9), struct cfg80211_update_owe_info(9), struct mgmt_frame_regs(9)

👑 ops, wiphy capabilities & combinations

struct cfg80211_ops(9), enum wiphy_flags(9), struct ieee80211_iface_limit(9), struct ieee80211_iface_combination(9), enum wiphy_wowlan_support_flags(9), struct wiphy_wowlan_support(9), struct wiphy_coalesce_support(9), enum wiphy_vendor_command_flags(9), enum wiphy_opmode_flag(9), struct sta_opmode_info(9), struct wiphy_vendor_command(9), struct wiphy_iftype_ext_capab(9), cfg80211_get_iftype_ext_capa(9), struct cfg80211_pmsr_capabilities(9), struct wiphy_iftype_akm_suites(9), struct wiphy_radio_cfg(9), struct wiphy_radio_freq_range(9), struct wiphy_radio(9), enum wiphy_nan_flags(9), struct wiphy_nan_capa(9)

🌈 the wiphy lifecycle & locking girlies

struct wiphy(9), wiphy_priv(9), priv_to_wiphy(9), set_wiphy_dev(9), wiphy_dev(9), wiphy_name(9), wiphy_new_nm(9), wiphy_new(9), wiphy_register(9), rcu_dereference_wiphy(9), wiphy_dereference(9), get_wiphy_regdom(9), wiphy_unregister(9), wiphy_free(9), wiphy_lock(9), wiphy_unlock(9)
wiphy_work_queue(9), wiphy_work_cancel(9), wiphy_work_flush(9), wiphy_delayed_work_queue(9), wiphy_delayed_work_cancel(9), wiphy_delayed_work_flush(9), wiphy_delayed_work_pending(9), wiphy_hrtimer_work_queue(9), wiphy_hrtimer_work_cancel(9), wiphy_hrtimer_work_flush(9), wiphy_hrtimer_work_pending(9), enum ieee80211_ap_reg_power(9)

💜 wireless_dev trio

struct wireless_dev(9), wdev_priv(9), wdev_chandef(9)

__cfg80211_get_bss(9) has two underscores up front, and yes that means it's the lowkey internal one, respect the naming convention 😌

🔥 mlme notifications & failures

cfg80211_rx_mlme_mgmt(9), cfg80211_auth_timeout(9), struct cfg80211_rx_assoc_resp_data(9), cfg80211_rx_assoc_resp(9), struct cfg80211_assoc_failure(9), cfg80211_assoc_failure(9), cfg80211_tx_mlme_mgmt(9), cfg80211_rx_unprot_mlme_mgmt(9), cfg80211_michael_mic_failure(9), cfg80211_ibss_joined(9), cfg80211_notify_new_peer_candidate(9)

💀 rfkill, vendor commands & test mode

RFkill integration(9), wiphy_rfkill_set_hw_state_reason(9), wiphy_rfkill_start_polling(9), wiphy_rfkill_stop_polling(9), Vendor commands(9), cfg80211_vendor_cmd_alloc_reply_skb(9), cfg80211_vendor_cmd_reply(9), cfg80211_vendor_cmd_get_sender(9), cfg80211_vendor_event_alloc(9), cfg80211_vendor_event_alloc_ucast(9), cfg80211_vendor_event(9), Test mode(9), cfg80211_testmode_alloc_reply_skb(9), cfg80211_testmode_reply(9), cfg80211_testmode_alloc_event_skb(9), cfg80211_testmode_event(9)

⭐ connect / roam / disconnect results

struct cfg80211_fils_resp_params(9), struct cfg80211_connect_resp_params(9), cfg80211_connect_done(9), cfg80211_connect_bss(9), cfg80211_connect_result(9), cfg80211_connect_timeout(9), struct cfg80211_roam_info(9), cfg80211_roamed(9), cfg80211_port_authorized(9), cfg80211_disconnected(9), cfg80211_ready_on_channel(9), cfg80211_remain_on_channel_expired(9), cfg80211_tx_mgmt_expired(9)

🫶 station add/del & tid stats

cfg80211_sinfo_alloc_tid_stats(9), cfg80211_link_sinfo_alloc_tid_stats(9), cfg80211_sinfo_release_content(9), cfg80211_new_sta(9), cfg80211_del_sta_sinfo(9), cfg80211_del_sta(9), cfg80211_conn_failed(9), struct cfg80211_rx_info(9), cfg80211_rx_mgmt_ext(9), cfg80211_rx_mgmt_khz(9), cfg80211_rx_mgmt(9), struct cfg80211_tx_status(9), cfg80211_mgmt_tx_status_ext(9), cfg80211_mgmt_tx_status(9), cfg80211_control_port_tx_status(9), cfg80211_rx_control_port(9)

🌈 the notify-everyone section (cqm, radar, cac & co.)

cfg80211_cqm_rssi_notify(9), cfg80211_cqm_pktloss_notify(9), cfg80211_cqm_txe_notify(9), cfg80211_cqm_beacon_loss_notify(9), __cfg80211_radar_event(9), cfg80211_sta_opmode_change_notify(9), cfg80211_cac_event(9), cfg80211_background_cac_abort(9), cfg80211_gtk_rekey_notify(9), cfg80211_pmksa_candidate_notify(9), cfg80211_rx_spurious_frame(9), cfg80211_rx_unexpected_4addr_frame(9), cfg80211_probe_status(9), cfg80211_report_obss_beacon_khz(9), cfg80211_report_obss_beacon(9), struct cfg80211_beaconing_check_config(9)

and that's literally where this part stops — the list just keeps going in the next chunk, so don't go anywhere 🧚‍♀️

...and the list just keeps going, bestie. Like genuinely, the see-also section here is doing the absolute most 💅 so here's the whole rest of the crew, in order, no skips:

cfg80211_reg_check_beaconing(9) — checking if beaconing is even allowed, the pre-flight vibe check 🦋
cfg80211_reg_can_beacon(9) — the classic "can I beacon here" question
cfg80211_reg_can_beacon_relax(9) — same question, but with the rules loosened a lil bit
cfg80211_ch_switch_notify(9) — channel switch went through, tell everyone
cfg80211_ch_switch_started_notify(9) — channel switch just started, also tell everyone
ieee80211_operating_class_to_band(9) — operating class in, band out
ieee80211_operating_class_to_chandef(9) — operating class in, channel definition out
ieee80211_chandef_to_operating_class(9) — the reverse, obviously
ieee80211_chandef_to_khz(9) — channel definition, but make it kilohertz ✨
cfg80211_tdls_oper_request(9) — TDLS operation requests, very niche, very iconic
cfg80211_calculate_bitrate(9) — math time, let's compute a bitrate
cfg80211_unregister_wdev(9) — yeeting a wireless device registration
cfg80211_register_netdevice(9) — registering a netdevice instead
cfg80211_unregister_netdevice(9) — and un-registering it, the circle of life 🫶
struct cfg80211_ft_event_params(9) — the struct holding FT event params
cfg80211_ft_event(9) — the fast-transition event itself
cfg80211_get_p2p_attr(9) — grabbing a P2P attribute
ieee80211_ie_split_ric(9) — splitting information elements with RIC handling
ieee80211_ie_split(9) — splitting IEs, no RIC drama
ieee80211_fragment_element(9) — chopping an element into fragments 🔥
cfg80211_report_wowlan_wakeup(9) — WoWLAN woke up, here's the report
cfg80211_crit_proto_stopped(9) — critical protocol just said bye
ieee80211_get_num_supported_channels(9) — how many channels we got, counting time
cfg80211_check_combinations(9) — checking if your channel/interface combo even works
cfg80211_iter_combinations(9) — iterating over all the combos
cfg80211_get_radio_idx_by_chan(9) — which radio owns this channel, enquiring minds
cfg80211_stop_link(9) — stopping a single link
cfg80211_stop_iface(9) — stopping the whole interface
cfg80211_shutdown_all_interfaces(9) — stopping everything, nuclear option 💀
wiphy_ext_feature_set(9) — setting an extended wiphy feature bit
wiphy_ext_feature_isset(9) — asking if that bit is set
cfg80211_free_nan_func(9) — freeing a NAN function, clean up after yourself
struct cfg80211_nan_match_params(9) — the struct for NAN match params
cfg80211_nan_match(9) — NAN match happened
cfg80211_nan_func_terminated(9) — NAN function is done
cfg80211_nan_sched_update_done(9) — NAN schedule update finished
cfg80211_external_auth_request(9) — external auth, please advise
cfg80211_pmsr_report(9) — PMSR measurement report incoming
cfg80211_pmsr_complete(9) — PMSR run is complete
cfg80211_iftype_allowed(9) — is this interface type even permitted
cfg80211_assoc_comeback(9) — the assoc comeback timer situation
cfg80211_update_owe_info_event(9) — OWE info event, pushing updates
cfg80211_bss_flush(9) — flushing the BSS list, out with the old
cfg80211_bss_color_notify(9) — BSS color notification
cfg80211_obss_color_collision_notify(9) — oop, OBSS color collision, notify the world 😭
cfg80211_color_change_started_notify(9) — color change started
cfg80211_color_change_aborted_notify(9) — color change aborted, we don't talk about it
cfg80211_color_change_notify(9) — color change, done and dusted
cfg80211_6ghz_power_type(9) — 6 GHz power type stuff, very new-school
cfg80211_links_removed(9) — links got removed
struct cfg80211_mlo_reconf_done_data(9) — the struct for MLO reconfig done data
cfg80211_mlo_reconf_add_done(9) — MLO reconfig add finished
cfg80211_schedule_channels_check(9) — scheduling a channels check
cfg80211_epcs_changed(9) — EPCS changed, noting it
cfg80211_next_nan_dw_notif(9) — next NAN discovery window notification
cfg80211_nan_cluster_joined(9) — you joined a NAN cluster, slay
cfg80211_nan_ulw_update(9) — NAN ULW update
cfg80211_nan_channel_evac(9) — NAN channel evacuation, everybody out 🏃‍♀️
wiphy_locked_debugfs_read(9) — debugfs read while holding the wiphy lock
wiphy_locked_debugfs_write(9) — and the write counterpart
cfg80211_s1g_get_start_freq_khz(9) — S1G start frequency in kHz
cfg80211_s1g_get_end_freq_khz(9) — S1G end frequency in kHz
cfg80211_s1g_get_primary_sibling(9) — the S1G primary sibling, as one does
cfg80211_incumbent_signal_notify(9) — incumbent signal spotted, notify the appropriate people 📡

okay that's literally the whole page, bestie, we made it 🎀 Take a sip of water, you've earned it.

This one's shipped straight out of ./include/net, dated October 2026, and it's the cfg80211_chandef_dfs_usable(9) page — go forth and check those DFS channel definitions responsibly, iykyk 💜

📦 where this page comes from

nixpkgs unstable: linux-manual 7.3.1
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms

cfg80211_chandef_dfs_usable(9)