NFC: Modified hci_transceive to become an asynchronous operation

This enables the completion callback to be called from a different
context, preventing a possible deadlock if the callback resulted in the
invocation of a nested call to the currently locked nfc_dev.
This is also more in line with the im_transceive nfc_ops for NFC Core or
NCI drivers which already behave asynchronously.

Signed-off-by: Eric Lapuyade <eric.lapuyade@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

2 files changed, 42 insertions, 20 deletions

diff --git a/net/nfc/hci/core.c b/net/nfc/hci/core.c
index e387c86e0cc7..dc57e3dc15a4 100644
--- a/net/nfc/hci/core.c
+++ b/net/nfc/hci/core.c
@@ -537,13 +537,37 @@ static void hci_deactivate_target(struct nfc_dev *nfc_dev,
 {
 }
 
+#define HCI_CB_TYPE_TRANSCEIVE 1
+
+static void hci_transceive_cb(void *context, struct sk_buff *skb, int err)
+{
+        struct nfc_hci_dev *hdev = context;
+
+        switch (hdev->async_cb_type) {
+        case HCI_CB_TYPE_TRANSCEIVE:
+                /*
+                 * TODO: Check RF Error indicator to make sure data is valid.
+                 * It seems that HCI cmd can complete without error, but data
+                 * can be invalid if an RF error occured? Ignore for now.
+                 */
+                if (err == 0)
+                        skb_trim(skb, skb->len - 1); /* RF Err ind */
+
+                hdev->async_cb(hdev->async_cb_context, skb, err);
+                break;
+        default:
+                if (err == 0)
+                        kfree_skb(skb);
+                break;
+        }
+}
+
 static int hci_transceive(struct nfc_dev *nfc_dev, struct nfc_target *target,
                           struct sk_buff *skb, data_exchange_cb_t cb,
                           void *cb_context)
 {
         struct nfc_hci_dev *hdev = nfc_get_drvdata(nfc_dev);
         int r;
-        struct sk_buff *res_skb = NULL;
 
         pr_debug("target_idx=%d\n", target->idx);
 
@@ -551,40 +575,37 @@ static int hci_transceive(struct nfc_dev *nfc_dev, struct nfc_target *target,
         case NFC_HCI_RF_READER_A_GATE:
         case NFC_HCI_RF_READER_B_GATE:
                 if (hdev->ops->data_exchange) {
-                        r = hdev->ops->data_exchange(hdev, target, skb,
-                                                     &res_skb);
+                        r = hdev->ops->data_exchange(hdev, target, skb, cb,
+                                                     cb_context);
                         if (r <= 0)     /* handled */
                                 break;
                 }
 
                 *skb_push(skb, 1) = 0;  /* CTR, see spec:10.2.2.1 */
-                r = nfc_hci_send_cmd(hdev, target->hci_reader_gate,
-                                     NFC_HCI_WR_XCHG_DATA,
-                                     skb->data, skb->len, &res_skb);
-                /*
-                 * TODO: Check RF Error indicator to make sure data is valid.
-                 * It seems that HCI cmd can complete without error, but data
-                 * can be invalid if an RF error occured? Ignore for now.
-                 */
-                if (r == 0)
-                        skb_trim(res_skb, res_skb->len - 1); /* RF Err ind */
+
+                hdev->async_cb_type = HCI_CB_TYPE_TRANSCEIVE;
+                hdev->async_cb = cb;
+                hdev->async_cb_context = cb_context;
+
+                r = nfc_hci_send_cmd_async(hdev, target->hci_reader_gate,
+                                           NFC_HCI_WR_XCHG_DATA, skb->data,
+                                           skb->len, hci_transceive_cb, hdev);
                 break;
         default:
                 if (hdev->ops->data_exchange) {
-                        r = hdev->ops->data_exchange(hdev, target, skb,
-                                                     &res_skb);
+                        r = hdev->ops->data_exchange(hdev, target, skb, cb,
+                                                     cb_context);
                         if (r == 1)
                                 r = -ENOTSUPP;
                 }
                 else
                         r = -ENOTSUPP;
+                break;
         }
 
         kfree_skb(skb);
 
-        cb(cb_context, res_skb, r);
-
-        return 0;
+        return r;
 }
 
 static int hci_check_presence(struct nfc_dev *nfc_dev,
diff --git a/net/nfc/hci/shdlc.c b/net/nfc/hci/shdlc.c
index 9357ba7362f6..c63af7d3e859 100644
--- a/net/nfc/hci/shdlc.c
+++ b/net/nfc/hci/shdlc.c
@@ -777,12 +777,13 @@ static int nfc_shdlc_complete_target_discovered(struct nfc_hci_dev *hdev,
 static int nfc_shdlc_data_exchange(struct nfc_hci_dev *hdev,
                                    struct nfc_target *target,
                                    struct sk_buff *skb,
-                                   struct sk_buff **res_skb)
+                                   data_exchange_cb_t cb, void *cb_context)
 {
         struct nfc_shdlc *shdlc = nfc_hci_get_clientdata(hdev);
 
         if (shdlc->ops->data_exchange)
-                return shdlc->ops->data_exchange(shdlc, target, skb, res_skb);
+                return shdlc->ops->data_exchange(shdlc, target, skb, cb,
+                                                 cb_context);
 
         return -EPERM;
 }