new properties to tune timeouts:

- add nfc_properties (will replace nfc_options)
 - introduce some error codes
 - rework functions to use the new timeout_command value

include/nfc/nfc-types.h

@@ -74,6 +74,30 @@ typedef struct {
  */
 typedef char nfc_connstring[1024];
 
+/**
+ * Properties
+ */
+typedef enum {
+/** 
+ * Default command processing timeout
+ * Property value's (duration) unit is ms and 0 means no timeout (infinite).
+ * Default value is set by driver layer
+ */
+  NP_TIMEOUT_COMMAND,
+/** 
+ * Timeout between ATR_REQ and ATR_RES
+ * When the device is in initiator mode, a target is considered as mute if no
+ * valid ATR_RES is received within this timeout value.
+ * Default value for this property is 103 ms on PN53x based devices.
+ */
+  NP_TIMEOUT_ATR,
+/**
+ * Timeout value to give up reception from the target in case of no answer.
+ * Default value for this property is 52 ms).
+ */
+  NP_TIMEOUT_COM,
+} nfc_property;
+
 // Compiler directive, set struct alignment to 1 uint8_t for compatibility
 #  pragma pack(1)
 

include/nfc/nfc.h

@@ -98,12 +98,22 @@ extern  "C" {
 /* Special data accessors */
   NFC_EXPORT const char *nfc_device_name (nfc_device *pnd);
 
+/* Properties accessors */
+  NFC_EXPORT int nfc_device_set_property_int (nfc_device *pnd, const nfc_property property, const int value);
+//  NFC_EXPORT int nfc_device_set_property_bool (nfc_device *pnd, const nfc_property property, const int value);
+
 /* Misc. functions */
   NFC_EXPORT void iso14443a_crc (uint8_t *pbtData, size_t szLen, uint8_t *pbtCrc);
   NFC_EXPORT void iso14443a_crc_append (uint8_t *pbtData, size_t szLen);
   NFC_EXPORT uint8_t *iso14443a_locate_historical_bytes (uint8_t *pbtAts, size_t szAts, size_t *pszTk);
   NFC_EXPORT const char *nfc_version (void);
 
+/* Error codes */
+#define NFC_SUCCESS		 0	// No error
+#define NFC_EIO			-1	// Input / output error, device will not be usable anymore
+#define NFC_ENOTSUP		-2	// Operation not supported
+#define NFC_EINVARG		-3	// Invalid argument(s)
+
 /* PN53x specific errors */
 // TODO: Be not PN53x-specific here
 #define ETIMEOUT	0x01