[PATCH wireless-next v3 01/21] wifi: nl80211: define Seamless Mobility Domain (SMD) device capability

[Pooventhiran G]

Per IEEE P802.11bn/D2.0, Aug 2026, subclause 37.16, an AP MLD can be
managed by a Seamless Mobility Domain Management Entity (SMD-ME) along
with partner AP MLDs to enable seamless transition of an associated
non-AP MLD from the current AP MLD to a target AP MLD. A non-AP MLD
advertising SMD supports association to an SMD-ME and SMD BSS
Transition between AP MLDs within an SMD.

Userspace needs a way to be aware of the driver's SMD capabilities so that
it can enable SMD configuration and operation only on capable devices.
Define nl80211 and wiphy flag interfaces to advertise SMD support to
userspace.

Co-developed-by: Rohan Dutta <drohan@xxxxxxxxxxxxxxxx>
Signed-off-by: Rohan Dutta <drohan@xxxxxxxxxxxxxxxx>
Signed-off-by: Pooventhiran G <pooventhiran.g@xxxxxxxxxxxxxxxx>
---
 include/net/cfg80211.h       |  3 +++
 include/uapi/linux/nl80211.h | 25 +++++++++++++++++++++++++
 net/wireless/nl80211.c       |  7 +++++++
 3 files changed, 35 insertions(+)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 46ba0fb27b14..b4f384ade47a 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -5796,6 +5796,8 @@ struct cfg80211_ops {
  *	STA) basis for station and P2P client interfaces.
  *	(Note that if userspace doesn't give the MAC address, the AP's address
  *	is substituted to allow for older userspace versions.)
+ * @WIPHY_FLAG_SUPPORTS_SMD: The device supports Seamless Mobility Domain (SMD)
+ *	setup and BSS Transition.
  */
 enum wiphy_flags {
 	WIPHY_FLAG_SUPPORTS_EXT_KEK_KCK		= BIT(0),
@@ -5823,6 +5825,7 @@ enum wiphy_flags {
 	WIPHY_FLAG_HAS_CHANNEL_SWITCH		= BIT(23),
 	WIPHY_FLAG_NOTIFY_REGDOM_BY_DRIVER	= BIT(24),
 	WIPHY_FLAG_CHANNEL_CHANGE_ON_BEACON     = BIT(25),
+	WIPHY_FLAG_SUPPORTS_SMD			= BIT(26),
 };
 
 /**
diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index b56a96f57bec..3e71564ce87c 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -343,6 +343,26 @@
  * processing of peer DH IE to generate PMK.
  */
 
+/**
+ * DOC: Seamless Mobility Domain (AP)
+ *
+ * Seamless Mobility Domain (SMD) is a mobility domain consisting of multiple
+ * non-colocated AP multi-link devices where a non-AP MLD can perform SMD BSS
+ * Transition (ST) between the AP MLDs without reassociation (hence, seamless).
+ * ST is done in two phases:
+ *	Preparation (where the target AP MLD sets up the links for the non-AP
+ *	MLD but keep in powersave) and
+ *	Execution (actual roaming where the non-AP MLD transitions to the
+ *	target AP MLD and continues traffic).
+ *
+ * To use this in nl80211, multiple commands carry the %NL80211_ATTR_SMD_SUPPORT
+ * attribute:
+ *	Drivers set %WIPHY_FLAG_SUPPORTS_SMD to indicate userspace about the
+ *	SMD capability in %NL80211_CMD_GET_WIPHY.
+ *	%NL80211_CMD_START_AP carries %NL80211_ATTR_SMD_SUPPORT to indicate that
+ *	the AP affiliated to an AP MLD is part of an SMD.
+ */
+
 /**
  * enum nl80211_commands - supported nl80211 commands
  *
@@ -3243,6 +3263,9 @@ enum nl80211_commands {
  * @NL80211_ATTR_ASSOC_PROTECTED_TWT: Enable protected TWT for the association,
  *	requires protected TWT support (flag attribute)
  *
+ * @NL80211_ATTR_SMD_SUPPORT: Flag attribute to indicate SMD support. Used with
+ *	multiple commands to indicate appropriate SMD support (refer DOC).
+ *
  * @NUM_NL80211_ATTR: total number of nl80211_attrs available
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
@@ -3850,6 +3873,8 @@ enum nl80211_attrs {
 
 	NL80211_ATTR_ASSOC_PROTECTED_TWT,
 
+	NL80211_ATTR_SMD_SUPPORT,
+
 	/* add attributes here, update the policy in nl80211.c */
 
 	__NL80211_ATTR_AFTER_LAST,
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 2fc680382418..16d00ebed10a 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -1201,6 +1201,7 @@ static const struct nla_policy nl80211_policy[NUM_NL80211_ATTR] = {
 	[NL80211_ATTR_ASSOC_CIP] = { .type = NLA_FLAG },
 	[NL80211_ATTR_CIP_CAPABILITIES] = { .type = NLA_U8 },
 	[NL80211_ATTR_ASSOC_PROTECTED_TWT] = { .type = NLA_FLAG },
+	[NL80211_ATTR_SMD_SUPPORT] = { .type = NLA_FLAG },
 };
 
 /* policy for the key attributes */
@@ -3824,6 +3825,12 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *rdev,
 		if (nl80211_put_nan_capa(&rdev->wiphy, msg))
 			goto nla_put_failure;
 
+		state->split_start++;
+		break;
+	case 19:
+		if (rdev->wiphy.flags & WIPHY_FLAG_SUPPORTS_SMD)
+			nla_put_flag(msg, NL80211_ATTR_SMD_SUPPORT);
+
 		/* done */
 		state->split_start = 0;
 		break;

-- 
2.34.1