NFC: Define secure element IO API and commands

In order to send and receive ISO7816 APDUs to and from NFC embedded
secure elements, we define a specific netlink command.
On a typical SE use case, host applications will send very few APDUs
(Less than 10) per transaction. This is why we decided to go for a
simple netlink API. Defining another NFC socket protocol for such low
traffic would have been overengineered.

Signed-off-by: Samuel Ortiz <[e-mail]>

include/net/nfc/nfc.h

···
 typedef void (*data_exchange_cb_t)(void *context, struct sk_buff *skb,
 								int err);
 
+typedef void (*se_io_cb_t)(void *context, u8 *apdu, size_t apdu_len, int err);
+
 struct nfc_target;
 
 struct nfc_ops {
···
 	int (*discover_se)(struct nfc_dev *dev);
 	int (*enable_se)(struct nfc_dev *dev, u32 se_idx);
 	int (*disable_se)(struct nfc_dev *dev, u32 se_idx);
+	int (*se_io) (struct nfc_dev *dev, u32 se_idx,
+		      u8 *apdu, size_t apdu_length,
+		      se_io_cb_t cb, void *cb_context);
 };
 
 #define NFC_TARGET_IDX_ANY -1

include/uapi/linux/nfc.h

···
  *	a specific SE notifies us about the end of a transaction. The parameter
  *	for this event is the application ID (AID).
  * @NFC_CMD_GET_SE: Dump all discovered secure elements from an NFC controller.
+ * @NFC_CMD_SE_IO: Send/Receive APDUs to/from the selected secure element.
  */
 enum nfc_commands {
 	NFC_CMD_UNSPEC,
···
 	NFC_EVENT_SE_CONNECTIVITY,
 	NFC_EVENT_SE_TRANSACTION,
 	NFC_CMD_GET_SE,
+	NFC_CMD_SE_IO,
 /* private: internal use only */
 	__NFC_CMD_AFTER_LAST
 };
···
  * @NFC_ATTR_SE_INDEX: Secure element index
  * @NFC_ATTR_SE_TYPE: Secure element type (UICC or EMBEDDED)
  * @NFC_ATTR_FIRMWARE_DOWNLOAD_STATUS: Firmware download operation status
+ * @NFC_ATTR_APDU: Secure element APDU
  */
 enum nfc_attrs {
 	NFC_ATTR_UNSPEC,
···
 	NFC_ATTR_SE_TYPE,
 	NFC_ATTR_SE_AID,
 	NFC_ATTR_FIRMWARE_DOWNLOAD_STATUS,
+	NFC_ATTR_SE_APDU,
 /* private: internal use only */
 	__NFC_ATTR_AFTER_LAST
 };