ieee802154: rework wpan_phy index assignment

This patch reworks the wpan_phy index incrementation. It's now similar
like wireless wiphy index incrementation. We move the wpan_phy index
attribute inside of cfg802154_registered_device and use atomic
operations instead locking mechanism via wpan_phy_mutex.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

2 files changed, 14 insertions, 19 deletions

diff --git a/net/ieee802154/core.c b/net/ieee802154/core.c
index ed5b014dbec7..d1cd0edfb149 100644
--- a/net/ieee802154/core.c
+++ b/net/ieee802154/core.c
@@ -23,9 +23,6 @@
 #include "sysfs.h"
 #include "core.h"
 
-static DEFINE_MUTEX(wpan_phy_mutex);
-static int wpan_phy_idx;
-
 static int wpan_phy_match(struct device *dev, const void *data)
 {
         return !strcmp(dev_name(dev), (const char *)data);
@@ -72,14 +69,10 @@ int wpan_phy_for_each(int (*fn)(struct wpan_phy *phy, void *data),
 }
 EXPORT_SYMBOL(wpan_phy_for_each);
 
-static int wpan_phy_idx_valid(int idx)
-{
-        return idx >= 0;
-}
-
 struct wpan_phy *
 wpan_phy_alloc(const struct cfg802154_ops *ops, size_t priv_size)
 {
+        static atomic_t wpan_phy_counter = ATOMIC_INIT(0);
         struct cfg802154_registered_device *rdev;
         size_t alloc_size;
 
@@ -90,28 +83,27 @@ wpan_phy_alloc(const struct cfg802154_ops *ops, size_t priv_size)
 
         rdev->ops = ops;
 
-        mutex_lock(&wpan_phy_mutex);
-        rdev->wpan_phy.idx = wpan_phy_idx++;
-        if (unlikely(!wpan_phy_idx_valid(rdev->wpan_phy.idx))) {
-                wpan_phy_idx--;
-                mutex_unlock(&wpan_phy_mutex);
+        rdev->wpan_phy_idx = atomic_inc_return(&wpan_phy_counter);
+
+        if (unlikely(rdev->wpan_phy_idx < 0)) {
+                /* ugh, wrapped! */
+                atomic_dec(&wpan_phy_counter);
                 kfree(rdev);
-                goto out;
+                return NULL;
         }
-        mutex_unlock(&wpan_phy_mutex);
+
+        /* atomic_inc_return makes it start at 1, make it start at 0 */
+        rdev->wpan_phy_idx--;
 
         mutex_init(&rdev->wpan_phy.pib_lock);
 
         device_initialize(&rdev->wpan_phy.dev);
-        dev_set_name(&rdev->wpan_phy.dev, "wpan-phy%d", rdev->wpan_phy.idx);
+        dev_set_name(&rdev->wpan_phy.dev, "wpan-phy%d", rdev->wpan_phy_idx);
 
         rdev->wpan_phy.dev.class = &wpan_phy_class;
         rdev->wpan_phy.dev.platform_data = rdev;
 
         return &rdev->wpan_phy;
-
-out:
-        return NULL;
 }
 EXPORT_SYMBOL(wpan_phy_alloc);
 
diff --git a/net/ieee802154/core.h b/net/ieee802154/core.h
index 1bc172587157..fea60b3a8846 100644
--- a/net/ieee802154/core.h
+++ b/net/ieee802154/core.h
@@ -6,6 +6,9 @@
 struct cfg802154_registered_device {
         const struct cfg802154_ops *ops;
 
+        /* wpan_phy index, internal only */
+        int wpan_phy_idx;
+
         /* must be last because of the way we do wpan_phy_priv(),
          * and it should at least be aligned to NETDEV_ALIGN
          */