Re: [PATCH wireless-next v2 09/18] wifi: cfg80211: document wiphy mutex for radar/CAC events

[Brian Norris <briannorris@chromium.org>]

On Mon, Oct 05, 2026 at 12:03:36PM +0200, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@intel.com>
> 
> The DFS state of channels and the CAC state of the wdev is
> protected by the wiphy mutex, so the radar and CAC events
> must be reported by drivers with the wiphy mutex held. In
> mac80211 we do this, but some drivers don't yet:
>  - mwifiex/nxpwifi have an event handling worker,

FWIW, one of the two contexts that call cfg80211_cac_event() in mwifiex
does *not* (by inspection) seem to hold this. Is this something you'd
prefer individual driver users/maintainers resolve?

>  - qtnfmac also does it from event processing, and
>  - mt7915 and mt7996 don't acquire a mutex for background
>    radar events.
> 
> Document the requirement.
> 
> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
> ---
>  include/net/cfg80211.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
> index 9cb536fc8cb8..eb376a54a07f 100644
> --- a/include/net/cfg80211.h
> +++ b/include/net/cfg80211.h
> @@ -9794,6 +9794,7 @@ void cfg80211_cqm_beacon_loss_notify(struct net_device *dev, gfp_t gfp);
>   * @gfp: context flags
>   *
>   * This function is called when a radar is detected on the current chanenl.
> + * Must be called with the wiphy mutex held.
>   */
>  void __cfg80211_radar_event(struct wiphy *wiphy,
>  			    struct cfg80211_chan_def *chandef,
> @@ -9839,7 +9840,7 @@ void cfg80211_sta_opmode_change_notify(struct net_device *dev, const u8 *mac,
>   *
>   * This function is called when a Channel availability check (CAC) is finished
>   * or aborted. This must be called to notify the completion of a CAC process,
> - * also by full-MAC drivers.
> + * also by full-MAC drivers. Must be called with the wiphy mutex held.
>   */
>  void cfg80211_cac_event(struct net_device *netdev,
>  			const struct cfg80211_chan_def *chandef,

Should we add an assert to this API?

	lockdep_assert_wiphy(wiphy);

> -- 
> 2.55.0
> 
>