cfg80211: support creating wiphy with suggested name

Kernel will attempt to use the name if it is supplied,
but if name cannot be used for some reason, the default
phyX name will be used instead.
Signed-off-by: Ben Greear <greearb@candelatech.com>
[while at it, use wiphy_name() instead of dev_name(),
 fix format string issue reported by Kees Cook]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -3184,6 +3184,23 @@ static inline const char *wiphy_name(const struct wiphy *wiphy)
 	return dev_name(&wiphy->dev);
 }
 
+/**
+ * wiphy_new_nm - create a new wiphy for use with cfg80211
+ *
+ * @ops: The configuration operations for this device
+ * @sizeof_priv: The size of the private area to allocate
+ * @requested_name: Request a particular name.
+ *	NULL is valid value, and means use the default phy%d naming.
+ *
+ * Create a new wiphy and associate the given operations with it.
+ * @sizeof_priv bytes are allocated for private use.
+ *
+ * Return: A pointer to the new wiphy. This pointer must be
+ * assigned to each netdev's ieee80211_ptr for proper operation.
+ */
+struct wiphy *wiphy_new_nm(const struct cfg80211_ops *ops, int sizeof_priv,
+			   const char *requested_name);
+
 /**
  * wiphy_new - create a new wiphy for use with cfg80211
  *
@@ -3196,7 +3213,11 @@ static inline const char *wiphy_name(const struct wiphy *wiphy)
  * Return: A pointer to the new wiphy. This pointer must be
  * assigned to each netdev's ieee80211_ptr for proper operation.
  */
-struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv);
+static inline struct wiphy *wiphy_new(const struct cfg80211_ops *ops,
+				      int sizeof_priv)
+{
+	return wiphy_new_nm(ops, sizeof_priv, NULL);
+}
 
 /**
  * wiphy_register - register a wiphy with cfg80211

net/wireless/core.c

@@ -86,11 +86,11 @@ struct wiphy *wiphy_idx_to_wiphy(int wiphy_idx)
 	return &rdev->wiphy;
 }
 
-int cfg80211_dev_rename(struct cfg80211_registered_device *rdev,
-			char *newname)
+static int cfg80211_dev_check_name(struct cfg80211_registered_device *rdev,
+				   const char *newname)
 {
 	struct cfg80211_registered_device *rdev2;
-	int wiphy_idx, taken = -1, result, digits;
+	int wiphy_idx, taken = -1, digits;
 
 	ASSERT_RTNL();
 
@@ -109,15 +109,28 @@ int cfg80211_dev_rename(struct cfg80211_registered_device *rdev,
 			return -EINVAL;
 	}
 
+	/* Ensure another device does not already have this name. */
+	list_for_each_entry(rdev2, &cfg80211_rdev_list, list)
+		if (strcmp(newname, wiphy_name(&rdev2->wiphy)) == 0)
+			return -EINVAL;
+
+	return 0;
+}
+
+int cfg80211_dev_rename(struct cfg80211_registered_device *rdev,
+			char *newname)
+{
+	int result;
+
+	ASSERT_RTNL();
 
 	/* Ignore nop renames */
-	if (strcmp(newname, dev_name(&rdev->wiphy.dev)) == 0)
+	if (strcmp(newname, wiphy_name(&rdev->wiphy)) == 0)
 		return 0;
 
-	/* Ensure another device does not already have this name. */
-	list_for_each_entry(rdev2, &cfg80211_rdev_list, list)
-		if (strcmp(newname, dev_name(&rdev2->wiphy.dev)) == 0)
-			return -EINVAL;
+	result = cfg80211_dev_check_name(rdev, newname);
+	if (result < 0)
+		return result;
 
 	result = device_rename(&rdev->wiphy.dev, newname);
 	if (result)
@@ -309,7 +322,8 @@ static void cfg80211_destroy_iface_wk(struct work_struct *work)
 
 /* exported functions */
 
-struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv)
+struct wiphy *wiphy_new_nm(const struct cfg80211_ops *ops, int sizeof_priv,
+			   const char *requested_name)
 {
 	static atomic_t wiphy_counter = ATOMIC_INIT(0);
 
@@ -346,7 +360,31 @@ struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv)
 	rdev->wiphy_idx--;
 
 	/* give it a proper name */
-	dev_set_name(&rdev->wiphy.dev, PHY_NAME "%d", rdev->wiphy_idx);
+	if (requested_name && requested_name[0]) {
+		int rv;
+
+		rtnl_lock();
+		rv = cfg80211_dev_check_name(rdev, requested_name);
+
+		if (rv < 0) {
+			rtnl_unlock();
+			goto use_default_name;
+		}
+
+		rv = dev_set_name(&rdev->wiphy.dev, "%s", requested_name);
+		rtnl_unlock();
+		if (rv)
+			goto use_default_name;
+	} else {
+use_default_name:
+		/* NOTE:  This is *probably* safe w/out holding rtnl because of
+		 * the restrictions on phy names.  Probably this call could
+		 * fail if some other part of the kernel (re)named a device
+		 * phyX.  But, might should add some locking and check return
+		 * value, and use a different name if this one exists?
+		 */
+		dev_set_name(&rdev->wiphy.dev, PHY_NAME "%d", rdev->wiphy_idx);
+	}
 
 	INIT_LIST_HEAD(&rdev->wdev_list);
 	INIT_LIST_HEAD(&rdev->beacon_registrations);
@@ -406,7 +444,7 @@ struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv)
 
 	return &rdev->wiphy;
 }
-EXPORT_SYMBOL(wiphy_new);
+EXPORT_SYMBOL(wiphy_new_nm);
 
 static int wiphy_verify_combinations(struct wiphy *wiphy)
 {