The patch:

commit 15e473046cb6e5d18a4d0057e61d76315230382b
Author: Eric W. Biederman <ebiederm@xmission.com>
Date:   Fri Sep 7 20:12:54 2012 +0000

    netlink: Rename pid to portid to avoid confusion
    
    It is a frequent mistake to confuse the netlink port identifier with a
    process identifier.  Try to reduce this confusion by renaming fields
    that hold port identifiers portid instead of pid.
    
    I have carefully avoided changing the structures exported to
    userspace to avoid changing the userspace API.
    
    I have successfully built an allyesconfig kernel with this change.
    
    Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
    Acked-by: Stephen Hemminger <shemminger@vyatta.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Changed the struct members:

struct netlink_notify->pid    to
struct netlink_notify->portid

struct genl_info->snd_pid     to
struct genl_info->snd_portid

To help backport this and not have to #ifdef around it against
kernel versions compat has introduced two helpers for us to
simply do the backport with two macro helpers:

genl_info_snd_portid()
netlink_notify_portid()

This takes care of the work for us requiring only one
single line change. If we get another patch thrown into
this file then I suspect we can extract SMPL out of it
and use it to backport further collateral evolutions like
this one should other drivers / subsystem need this change.

--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -2013,10 +2013,10 @@ static int hwsim_register_received_nl(st
 	if (info == NULL)
 		goto out;
 
-	wmediumd_portid = info->snd_portid;
+	wmediumd_portid = genl_info_snd_portid(info);
 
 	printk(KERN_DEBUG "mac80211_hwsim: received a REGISTER, "
-	       "switching to wmediumd mode with pid %d\n", info->snd_portid);
+	       "switching to wmediumd mode with pid %d\n", genl_info_snd_portid(info));
 
 	return 0;
 out:
@@ -2053,7 +2053,7 @@ static int mac80211_hwsim_netlink_notify
 	if (state != NETLINK_URELEASE)
 		return NOTIFY_DONE;
 
-	if (notify->portid == wmediumd_portid) {
+	if (netlink_notify_portid(notify) == wmediumd_portid) {
 		printk(KERN_INFO "mac80211_hwsim: wmediumd released netlink"
 		       " socket, switching to perfect channel medium\n");
 		wmediumd_portid = 0;
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -1593,7 +1593,7 @@ static int nl80211_dump_wiphy(struct sk_
 		/* attempt to fit multiple wiphy data chunks into the skb */
 		do {
 			ret = nl80211_send_wiphy(dev, skb,
-						 NETLINK_CB(cb->skb).portid,
+						 NETLINK_CB_PORTID(cb->skb),
 						 cb->nlh->nlmsg_seq,
 						 NLM_F_MULTI,
 						 split, &cb->args[1],
@@ -1642,7 +1642,7 @@ static int nl80211_get_wiphy(struct sk_b
 	if (!msg)
 		return -ENOMEM;
 
-	if (nl80211_send_wiphy(dev, msg, info->snd_portid, info->snd_seq, 0,
+	if (nl80211_send_wiphy(dev, msg, genl_info_snd_portid(info), info->snd_seq, 0,
 			       false, NULL, NULL, NULL) < 0) {
 		nlmsg_free(msg);
 		return -ENOBUFS;
@@ -2222,7 +2222,7 @@ static int nl80211_dump_interface(struct
 				if_idx++;
 				continue;
 			}
-			if (nl80211_send_iface(skb, NETLINK_CB(cb->skb).portid,
+			if (nl80211_send_iface(skb, NETLINK_CB_PORTID(cb->skb),
 					       cb->nlh->nlmsg_seq, NLM_F_MULTI,
 					       rdev, wdev) < 0) {
 				mutex_unlock(&rdev->devlist_mtx);
@@ -2253,7 +2253,7 @@ static int nl80211_get_interface(struct
 	if (!msg)
 		return -ENOMEM;
 
-	if (nl80211_send_iface(msg, info->snd_portid, info->snd_seq, 0,
+	if (nl80211_send_iface(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 			       dev, wdev) < 0) {
 		nlmsg_free(msg);
 		return -ENOBUFS;
@@ -2478,7 +2478,7 @@ static int nl80211_new_interface(struct
 		break;
 	}
 
-	if (nl80211_send_iface(msg, info->snd_portid, info->snd_seq, 0,
+	if (nl80211_send_iface(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 			       rdev, wdev) < 0) {
 		nlmsg_free(msg);
 		return -ENOBUFS;
@@ -2613,7 +2613,7 @@ static int nl80211_get_key(struct sk_buf
 	if (!msg)
 		return -ENOMEM;
 
-	hdr = nl80211hdr_put(msg, info->snd_portid, info->snd_seq, 0,
+	hdr = nl80211hdr_put(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 			     NL80211_CMD_NEW_KEY);
 	if (IS_ERR(hdr))
 		return PTR_ERR(hdr);
@@ -3549,7 +3549,7 @@ static int nl80211_dump_station(struct s
 			goto out_err;
 
 		if (nl80211_send_station(skb,
-				NETLINK_CB(cb->skb).portid,
+				NETLINK_CB_PORTID(cb->skb),
 				cb->nlh->nlmsg_seq, NLM_F_MULTI,
 				dev, netdev, mac_addr,
 				&sinfo) < 0)
@@ -3595,7 +3595,7 @@ static int nl80211_get_station(struct sk
 	if (!msg)
 		return -ENOMEM;
 
-	if (nl80211_send_station(msg, info->snd_portid, info->snd_seq, 0,
+	if (nl80211_send_station(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 				 rdev, dev, mac_addr, &sinfo) < 0) {
 		nlmsg_free(msg);
 		return -ENOBUFS;
@@ -4195,7 +4195,7 @@ static int nl80211_dump_mpath(struct sk_
 		if (err)
 			goto out_err;
 
-		if (nl80211_send_mpath(skb, NETLINK_CB(cb->skb).portid,
+		if (nl80211_send_mpath(skb, NETLINK_CB_PORTID(cb->skb),
 				       cb->nlh->nlmsg_seq, NLM_F_MULTI,
 				       netdev, dst, next_hop,
 				       &pinfo) < 0)
@@ -4244,7 +4244,7 @@ static int nl80211_get_mpath(struct sk_b
 	if (!msg)
 		return -ENOMEM;
 
-	if (nl80211_send_mpath(msg, info->snd_portid, info->snd_seq, 0,
+	if (nl80211_send_mpath(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 				 dev, dst, next_hop, &pinfo) < 0) {
 		nlmsg_free(msg);
 		return -ENOBUFS;
@@ -4508,7 +4508,7 @@ static int nl80211_get_mesh_config(struc
 	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
 	if (!msg)
 		return -ENOMEM;
-	hdr = nl80211hdr_put(msg, info->snd_portid, info->snd_seq, 0,
+	hdr = nl80211hdr_put(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 			     NL80211_CMD_GET_MESH_CONFIG);
 	if (!hdr)
 		goto out;
@@ -4858,7 +4858,7 @@ static int nl80211_get_reg(struct sk_buf
 		goto out;
 	}
 
-	hdr = nl80211hdr_put(msg, info->snd_portid, info->snd_seq, 0,
+	hdr = nl80211hdr_put(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 			     NL80211_CMD_GET_REG);
 	if (!hdr)
 		goto put_failure;
@@ -5545,7 +5545,7 @@ static int nl80211_send_bss(struct sk_bu
 
 	ASSERT_WDEV_LOCK(wdev);
 
-	hdr = nl80211hdr_put(msg, NETLINK_CB(cb->skb).portid, seq, flags,
+	hdr = nl80211hdr_put(msg, NETLINK_CB_PORTID(cb->skb), seq, flags,
 			     NL80211_CMD_NEW_SCAN_RESULTS);
 	if (!hdr)
 		return -1;
@@ -5776,7 +5776,7 @@ static int nl80211_dump_survey(struct sk
 		}
 
 		if (nl80211_send_survey(skb,
-				NETLINK_CB(cb->skb).portid,
+				NETLINK_CB_PORTID(cb->skb),
 				cb->nlh->nlmsg_seq, NLM_F_MULTI,
 				netdev,
 				&survey) < 0)
@@ -6435,7 +6435,7 @@ static int nl80211_testmode_dump(struct
 	}
 
 	while (1) {
-		void *hdr = nl80211hdr_put(skb, NETLINK_CB(cb->skb).portid,
+		void *hdr = nl80211hdr_put(skb, NETLINK_CB_PORTID(cb->skb),
 					   cb->nlh->nlmsg_seq, NLM_F_MULTI,
 					   NL80211_CMD_TESTMODE);
 		struct nlattr *tmdata;
@@ -6514,7 +6514,7 @@ struct sk_buff *cfg80211_testmode_alloc_
 		return NULL;
 
 	return __cfg80211_testmode_alloc_skb(rdev, approxlen,
-				rdev->testmode_info->snd_portid,
+				genl_info_snd_portid(rdev->testmode_info),
 				rdev->testmode_info->snd_seq,
 				GFP_KERNEL);
 }
@@ -6874,7 +6874,7 @@ static int nl80211_remain_on_channel(str
 	if (!msg)
 		return -ENOMEM;
 
-	hdr = nl80211hdr_put(msg, info->snd_portid, info->snd_seq, 0,
+	hdr = nl80211hdr_put(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 			     NL80211_CMD_REMAIN_ON_CHANNEL);
 
 	if (IS_ERR(hdr)) {
@@ -7093,7 +7093,7 @@ static int nl80211_register_mgmt(struct
 	if (!rdev->ops->mgmt_tx)
 		return -EOPNOTSUPP;
 
-	return cfg80211_mlme_register_mgmt(wdev, info->snd_portid, frame_type,
+	return cfg80211_mlme_register_mgmt(wdev, genl_info_snd_portid(info), frame_type,
 			nla_data(info->attrs[NL80211_ATTR_FRAME_MATCH]),
 			nla_len(info->attrs[NL80211_ATTR_FRAME_MATCH]));
 }
@@ -7163,7 +7163,7 @@ static int nl80211_tx_mgmt(struct sk_buf
 		if (!msg)
 			return -ENOMEM;
 
-		hdr = nl80211hdr_put(msg, info->snd_portid, info->snd_seq, 0,
+		hdr = nl80211hdr_put(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 				     NL80211_CMD_FRAME);
 
 		if (IS_ERR(hdr)) {
@@ -7278,7 +7278,7 @@ static int nl80211_get_power_save(struct
 	if (!msg)
 		return -ENOMEM;
 
-	hdr = nl80211hdr_put(msg, info->snd_portid, info->snd_seq, 0,
+	hdr = nl80211hdr_put(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 			     NL80211_CMD_GET_POWER_SAVE);
 	if (!hdr) {
 		err = -ENOBUFS;
@@ -7570,7 +7570,7 @@ static int nl80211_get_wowlan(struct sk_
 	if (!msg)
 		return -ENOMEM;
 
-	hdr = nl80211hdr_put(msg, info->snd_portid, info->snd_seq, 0,
+	hdr = nl80211hdr_put(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 			     NL80211_CMD_GET_WOWLAN);
 	if (!hdr)
 		goto nla_put_failure;
@@ -7994,7 +7994,7 @@ static int nl80211_register_unexpected_f
 	if (wdev->ap_unexpected_nlportid)
 		return -EBUSY;
 
-	wdev->ap_unexpected_nlportid = info->snd_portid;
+	wdev->ap_unexpected_nlportid = genl_info_snd_portid(info);
 	return 0;
 }
 
@@ -8024,7 +8024,7 @@ static int nl80211_probe_client(struct s
 	if (!msg)
 		return -ENOMEM;
 
-	hdr = nl80211hdr_put(msg, info->snd_portid, info->snd_seq, 0,
+	hdr = nl80211hdr_put(msg, genl_info_snd_portid(info), info->snd_seq, 0,
 			     NL80211_CMD_PROBE_CLIENT);
 
 	if (IS_ERR(hdr)) {
@@ -8068,13 +8068,13 @@ static int nl80211_register_beacons(stru
 	/* First, check if already registered. */
 	spin_lock_bh(&rdev->beacon_registrations_lock);
 	list_for_each_entry(reg, &rdev->beacon_registrations, list) {
-		if (reg->nlportid == info->snd_portid) {
+		if (reg->nlportid == genl_info_snd_portid(info)) {
 			rv = -EALREADY;
 			goto out_err;
 		}
 	}
 	/* Add it to the list */
-	nreg->nlportid = info->snd_portid;
+	nreg->nlportid = genl_info_snd_portid(info);
 	list_add(&nreg->list, &rdev->beacon_registrations);
 
 	spin_unlock_bh(&rdev->beacon_registrations_lock);
@@ -10563,12 +10563,12 @@ static int nl80211_netlink_notify(struct
 
 	list_for_each_entry_rcu(rdev, &cfg80211_rdev_list, list) {
 		list_for_each_entry_rcu(wdev, &rdev->wdev_list, list)
-			cfg80211_mlme_unregister_socket(wdev, notify->portid);
+			cfg80211_mlme_unregister_socket(wdev, netlink_notify_portid(notify));
 
 		spin_lock_bh(&rdev->beacon_registrations_lock);
 		list_for_each_entry_safe(reg, tmp, &rdev->beacon_registrations,
 					 list) {
-			if (reg->nlportid == notify->portid) {
+			if (reg->nlportid == netlink_notify_portid(notify)) {
 				list_del(&reg->list);
 				kfree(reg);
 				break;