nfc: st21nfca: Add additional comments about EVT_TRANSACTION

Add comments about HCI EVT_TRANSACTION in order to make the code
understandable by other readers.

Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/nfc/st21nfca/st21nfca_se.c b/drivers/nfc/st21nfca/st21nfca_se.c
index bd13cac9c66a..3197e9bb66f7 100644
--- a/drivers/nfc/st21nfca/st21nfca_se.c
+++ b/drivers/nfc/st21nfca/st21nfca_se.c
@@ -310,6 +310,13 @@ int st21nfca_connectivity_event_received(struct nfc_hci_dev *hdev, u8 host,
         case ST21NFCA_EVT_CONNECTIVITY:
                 break;
         case ST21NFCA_EVT_TRANSACTION:
+                /*
+                 * According to specification etsi 102 622
+                 * 11.2.2.4 EVT_TRANSACTION Table 52
+                 * Description  Tag     Length
+                 * AID          81      5 to 16
+                 * PARAMETERS   82      0 to 255
+                 */
                 if (skb->len < NFC_MIN_AID_LENGTH + 2 &&
                     skb->data[0] != NFC_EVT_TRANSACTION_AID_TAG)
                         return -EPROTO;
@@ -318,8 +325,10 @@ int st21nfca_connectivity_event_received(struct nfc_hci_dev *hdev, u8 host,
                                                    skb->len - 2, GFP_KERNEL);
 
                 transaction->aid_len = skb->data[1];
-                memcpy(transaction->aid, &skb->data[2], skb->data[1]);
+                memcpy(transaction->aid, &skb->data[2],
+                       transaction->aid_len);
 
+                /* Check next byte is PARAMETERS tag (82) */
                 if (skb->data[transaction->aid_len + 2] !=
                     NFC_EVT_TRANSACTION_PARAMS_TAG)
                         return -EPROTO;