NFC: Specify usage for targets found and target lost events

It is now specified that nfc_target_found() and nfc_target_lost() core
functions must not be called from an atomic context. This allow us to
serialize calls and protect the targets table using the nfc device lock
instead of a spinlock.

Signed-off-by: Eric Lapuyade <eric.lapuyade@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 28 insertions, 11 deletions

diff --git a/net/nfc/core.c b/net/nfc/core.c
index 7df28ad4727f..9f6ce011d35d 100644
--- a/net/nfc/core.c
+++ b/net/nfc/core.c
@@ -501,6 +501,9 @@ EXPORT_SYMBOL(nfc_alloc_recv_skb);
  * The device driver must call this function when one or many nfc targets
  * are found. After calling this function, the device driver must stop
  * polling for targets.
+ * IMPORTANT: this function must not be called from an atomic context.
+ * In addition, it must also not be called from a context that would prevent
+ * the NFC Core to call other nfc ops entry point concurrently.
  */
 int nfc_targets_found(struct nfc_dev *dev,
                       struct nfc_target *targets, int n_targets)
@@ -514,7 +517,7 @@ int nfc_targets_found(struct nfc_dev *dev,
         for (i = 0; i < n_targets; i++)
                 targets[i].idx = dev->target_next_idx++;
 
-        spin_lock_bh(&dev->targets_lock);
+        device_lock(&dev->dev);
 
         dev->targets_generation++;
 
@@ -524,12 +527,12 @@ int nfc_targets_found(struct nfc_dev *dev,
 
         if (!dev->targets) {
                 dev->n_targets = 0;
-                spin_unlock_bh(&dev->targets_lock);
+                device_unlock(&dev->dev);
                 return -ENOMEM;
         }
 
         dev->n_targets = n_targets;
-        spin_unlock_bh(&dev->targets_lock);
+        device_unlock(&dev->dev);
 
         nfc_genl_targets_found(dev);
 
@@ -537,6 +540,18 @@ int nfc_targets_found(struct nfc_dev *dev,
 }
 EXPORT_SYMBOL(nfc_targets_found);
 
+/**
+ * nfc_target_lost - inform that an activated target went out of field
+ *
+ * @dev: The nfc device that had the activated target in field
+ * @target_idx: the nfc index of the target
+ *
+ * The device driver must call this function when the activated target
+ * goes out of the field.
+ * IMPORTANT: this function must not be called from an atomic context.
+ * In addition, it must also not be called from a context that would prevent
+ * the NFC Core to call other nfc ops entry point concurrently.
+ */
 int nfc_target_lost(struct nfc_dev *dev, u32 target_idx)
 {
         struct nfc_target *tg;
@@ -544,7 +559,7 @@ int nfc_target_lost(struct nfc_dev *dev, u32 target_idx)
 
         pr_debug("dev_name %s n_target %d\n", dev_name(&dev->dev), target_idx);
 
-        spin_lock_bh(&dev->targets_lock);
+        device_lock(&dev->dev);
 
         for (i = 0; i < dev->n_targets; i++) {
                 tg = &dev->targets[i];
@@ -553,7 +568,7 @@ int nfc_target_lost(struct nfc_dev *dev, u32 target_idx)
         }
 
         if (i == dev->n_targets) {
-                spin_unlock_bh(&dev->targets_lock);
+                device_unlock(&dev->dev);
                 return -EINVAL;
         }
 
@@ -569,7 +584,7 @@ int nfc_target_lost(struct nfc_dev *dev, u32 target_idx)
                 dev->targets = NULL;
         }
 
-        spin_unlock_bh(&dev->targets_lock);
+        device_unlock(&dev->dev);
 
         nfc_genl_target_lost(dev, target_idx);
 
@@ -607,8 +622,10 @@ static void nfc_check_pres_work(struct work_struct *work)
                         mod_timer(&dev->check_pres_timer, jiffies +
                                   msecs_to_jiffies(NFC_CHECK_PRES_FREQ_MS));
                 } else {
-                        nfc_target_lost(dev, dev->active_target->idx);
-                        dev->active_target = NULL;
+                        u32 active_target_idx = dev->active_target->idx;
+                        device_unlock(&dev->dev);
+                        nfc_target_lost(dev, active_target_idx);
+                        return;
                 }
         }
 
@@ -681,9 +698,9 @@ struct nfc_dev *nfc_allocate_device(struct nfc_ops *ops,
         dev->tx_headroom = tx_headroom;
         dev->tx_tailroom = tx_tailroom;
 
-        spin_lock_init(&dev->targets_lock);
         nfc_genl_data_init(&dev->genl_data);
 
+
         /* first generation must not be 0 */
         dev->targets_generation = 1;
 
diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
index f1829f6ae9c5..77dae74832d3 100644
--- a/net/nfc/netlink.c
+++ b/net/nfc/netlink.c
@@ -128,7 +128,7 @@ static int nfc_genl_dump_targets(struct sk_buff *skb,
                 cb->args[1] = (long) dev;
         }
 
-        spin_lock_bh(&dev->targets_lock);
+        device_lock(&dev->dev);
 
         cb->seq = dev->targets_generation;
 
@@ -141,7 +141,7 @@ static int nfc_genl_dump_targets(struct sk_buff *skb,
                 i++;
         }
 
-        spin_unlock_bh(&dev->targets_lock);
+        device_unlock(&dev->dev);
 
         cb->args[0] = i;