Re: [PATCH wireless-next v2 02/16] wifi: nl80211: Add kernel interfaces for Seamless Mobility Domain setup

[Johannes Berg <johannes@sipsolutions.net>]

On Thu, 2026-09-24 at 08:10 +0530, Pooventhiran G wrote:
> 
> +++ b/include/uapi/linux/nl80211.h
> @@ -3190,6 +3190,12 @@ enum nl80211_commands {
>   *	known station to transmit a frame. This is relevant to know whether
>   *	MLD address translation happened or to disable it when sending a frame.
>   *
> + * @NL80211_ATTR_SMD_PARAMS: Nested attribute to indicate support for Seamless
> + *	Mobility Domain (SMD); it contains parameters to define capabilities of
> + *	an AP managed by an SMD-ME. Valid if the driver supports
> + *	%NL80211_EXT_FEATURE_SMD.
> + *	Used with %NL80211_CMD_START_AP. See &enum nl80211_smd_params_attrs.

"Valid if the driver supports" doesn't make sense - it should clearly be
arranged to be "valid if present" (which doesn't even need to be
stated). Then you can get rid of patch 1 entirely, though my request for
documentation still stands.

> +/**
> + * enum nl80211_smd_type - Type of the SMD
> + *
> + * @NL80211_SMD_TYPE_PER_AP_MLD_MAC_SAP: Separate MAC SAP is used per AP MLD.
> + * @NL80211_SMD_TYPE_PER_SMD_MAC_SAP: one MAC SAP is used in the SMD.
> + * @NUM_NL80211_SMD_TYPES: internal.
> + * @NL80211_SMD_TYPE_MAX: Max type of the SMD.
> + *
> + * This value represents the data path models between the non-AP MLD and DS.
> + * DS mapping for the non-AP MLD is updated if
> + * %NL80211_SMD_TYPE_PER_AP_MLD_MAC_SAP is used.
> + *
> + * All AP MLDs within an SMD shall indicate the same SMD type (refer
> + * IEEE P802.11bn/D2.0, Aug 2026, subclause 37.16.1.2).
> + */
> +enum nl80211_smd_type {
> +	NL80211_SMD_TYPE_PER_AP_MLD_MAC_SAP,
> +	NL80211_SMD_TYPE_PER_SMD_MAC_SAP,
> +
> +	NUM_NL80211_SMD_TYPES,
> +	NL80211_SMD_TYPE_MAX = NUM_NL80211_SMD_TYPES - 1,
> +};

I don't think this makes sense, any given driver might be able to
implement both.

> +/**
> + * enum nl80211_smd_ptk_mode - PTK Mode used in the SMD
> + *
> + * @NL80211_SMD_PTK_MODE_PER_SMD_PTK: one PTK is used by all AP MLDs in the SMD.
> + * @NL80211_SMD_PTK_MODE_PER_AP_MLD_PTK: Separate PTK is used per AP MLD.
> + * @NUM_NL80211_SMD_PTK_MODES: internal.
> + * @NL80211_SMD_PTK_MODE_MAX: Max type of PTK mode.
> + *
> + * This value represents the security mode of the SMD that dictates the PTK used
> + * in current and target AP MLDs to protect communications with the non-AP MLD
> + * (refer IEEE P802.11bn/D2.0, Aug 2026, subclause 37.16.1.3.2)
> + */
> +enum nl80211_smd_ptk_mode {
> +	NL80211_SMD_PTK_MODE_PER_SMD_PTK,
> +	NL80211_SMD_PTK_MODE_PER_AP_MLD_PTK,
> +
> +	NUM_NL80211_SMD_PTK_MODES,
> +	NL80211_SMD_PTK_MODE_MAX = NUM_NL80211_SMD_PTK_MODES - 1,
> +};

Same here.

> +/**
> + * enum nl80211_smd_params_attrs - SMD Domain parameters
> + *
> + * @NL80211_SMD_PARAMS_ATTR_UNSPEC: Invalid attribute.
> + * @NL80211_SMD_PARAMS_ATTR_IDENTIFIER: Required (binary) attribute of ETH_ALEN
> + *	bytes used to define the unique identifier for the SMD.

What? Surely you're not asking the driver to advertise the SMD ID vs.
hostapd just setting it, so I don't see how this makes sense?

> + * @NL80211_SMD_PARAMS_ATTR_TIMEOUT: Required (u16) attribute to define the SMD
> + *	Preparation timeout (in 64 TUs, values 0 and 1 are reserved) for
> + *	the target AP MLD.

Doesn't make sense either - if anything the driver might need to set a
minimum or something?

> + * @NL80211_SMD_PARAMS_ATTR_DL_DATA_FORWARDING: Flag attribute to indicate that
> + *	the device supports forwarding of buffered DL data packets.

What am I reading ... please get someone else to review this code first.

> + * @NL80211_SMD_PARAMS_ATTR_MAX_PEER_APMLDS: Required (u8) attribute to define
> + *	the maximum number of AP MLDs a non-AP MLD can prepare with. Value is
> + *	the maximum number of AP MLDs - 1. A value of 0 means that the non-AP
> + *	MLD can prepare with 1 AP MLD.

That doesn't make sense at the driver level at all, each individual
driver should have no notion of how many others a peer prepared with?

> + * @NL80211_SMD_PARAMS_ATTR_TYPE: Required (u8) attribute to indicate the
> + *	SMD Type (&enum nl80211_smd_type).
> + * @NL80211_SMD_PARAMS_ATTR_PTK_MODE: Required (u8) attribute to indicate the
> + *	PTK mode used for protection (&enum nl80211_smd_ptk_mode).

See above.

johannes