Re: [PATCH wireless-next 1/2] wifi: nl80211: Add NL80211_ATTR_MAX_CH_SWITCH_TIME attribute

[Johannes Berg <johannes@sipsolutions.net>]

On Mon, 2026-05-18 at 16:01 +0530, Shashikala Prabhu wrote:
> From: Chandru Gopi <cgopi@qti.qualcomm.com>
> 
> IEEE Std 802.11-2024 subclause 9.4.2.216 (Max Channel Switch Time element)
> defines a Switch Time field in the Channel Switch Announcement (CSA)
> element that indicates the time delta between the time the last beacon
> is transmitted by the AP in the current channel and the expected time
> of the first beacon transmitted by the AP in the new channel.
> 
> Add a new u32 nl80211 attribute, NL80211_ATTR_MAX_CH_SWITCH_TIME,
> to carry this value in the NL80211_CMD_CH_SWITCH_STARTED_NOTIFY
> event. Userspace can use this information to decide whether to
> remain connected or disconnect before the AP moves to the new
> channel.

This really confused me a lot because that event is used on both sides
... don't include the new netlink attribute when it's on the AP side.

Also bad split with the patches - make one cfg/nl80211 API patch, and
one mac80211 patch.

>  	NL80211_ATTR_NPCA_PUNCT_BITMAP,
>  
> +	NL80211_ATTR_MAX_CH_SWITCH_TIME,
>  	/* add attributes here, update the policy in nl80211.c */

nit: looks odd without the blank line

> +++ b/net/wireless/nl80211.c
> @@ -1093,6 +1093,7 @@ static const struct nla_policy nl80211_policy[NUM_NL80211_ATTR] = {
>  	[NL80211_ATTR_NPCA_PRIMARY_FREQ] = { .type = NLA_U32 },
>  	[NL80211_ATTR_NPCA_PUNCT_BITMAP] =
>  		NLA_POLICY_FULL_RANGE(NLA_U32, &nl80211_punct_bitmap_range),
> +	[NL80211_ATTR_MAX_CH_SWITCH_TIME] = { .type = NLA_U32 },

That seems wrong since it's output only, it shouldn't even be accepted
on input.

johannes