Merge branch 'for-thermal-genetlink-family-bind-unbind-callbacks'

Stanislaw Gruszka says:

====================
thermal/netlink/intel_hfi: Enable HFI feature only when required

The patchset introduces a new genetlink family bind/unbind callbacks
and thermal/netlink notifications, which allow drivers to send netlink
multicast events based on the presence of actual user-space consumers.
This functionality optimizes resource usage by allowing disabling
of features when not needed.

v1: https://lore.kernel.org/linux-pm/20240131120535.933424-1-stanislaw.gruszka@linux.intel.com//
v2: https://lore.kernel.org/linux-pm/20240206133605.1518373-1-stanislaw.gruszka@linux.intel.com/
v3: https://lore.kernel.org/linux-pm/20240209120625.1775017-1-stanislaw.gruszka@linux.intel.com/
====================

Link: https://lore.kernel.org/r/20240212161615.161935-1-stanislaw.gruszka@linux.intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/genetlink.h

@@ -41,6 +41,8 @@ struct genl_info;
  *	do additional, common, filtering and return an error
  * @post_doit: called after an operation's doit callback, it may
  *	undo operations done by pre_doit, for example release locks
+ * @bind: called when family multicast group is added to a netlink socket
+ * @unbind: called when family multicast group is removed from a netlink socket
  * @module: pointer to the owning module (set to THIS_MODULE)
  * @mcgrps: multicast groups used by this family
  * @n_mcgrps: number of multicast groups
@@ -84,6 +86,8 @@ struct genl_family {
 	void			(*post_doit)(const struct genl_split_ops *ops,
 					     struct sk_buff *skb,
 					     struct genl_info *info);
+	int			(*bind)(int mcgrp);
+	void			(*unbind)(int mcgrp);
 	const struct genl_ops *	ops;
 	const struct genl_small_ops *small_ops;
 	const struct genl_split_ops *split_ops;

net/netlink/genetlink.c

@@ -1836,6 +1836,9 @@ static int genl_bind(struct net *net, int group)
 		    !ns_capable(net->user_ns, CAP_SYS_ADMIN))
 			ret = -EPERM;
 
+		if (family->bind)
+			family->bind(i);
+
 		break;
 	}
 
@@ -1843,12 +1846,39 @@ static int genl_bind(struct net *net, int group)
 	return ret;
 }
 
+static void genl_unbind(struct net *net, int group)
+{
+	const struct genl_family *family;
+	unsigned int id;
+
+	down_read(&cb_lock);
+
+	idr_for_each_entry(&genl_fam_idr, family, id) {
+		int i;
+
+		if (family->n_mcgrps == 0)
+			continue;
+
+		i = group - family->mcgrp_offset;
+		if (i < 0 || i >= family->n_mcgrps)
+			continue;
+
+		if (family->unbind)
+			family->unbind(i);
+
+		break;
+	}
+
+	up_read(&cb_lock);
+}
+
 static int __net_init genl_pernet_init(struct net *net)
 {
 	struct netlink_kernel_cfg cfg = {
 		.input		= genl_rcv,
 		.flags		= NL_CFG_F_NONROOT_RECV,
 		.bind		= genl_bind,
+		.unbind		= genl_unbind,
 		.release	= genl_release,
 	};