freetdm: - Update ftmod_sangoma_isdn to use core state advance

- Added locking documentation (docs/locking.txt)
	 - Updated core state advance to use state processor in span
           rather than pushing the processor in the function arguments

libs/freetdm/src/include/freetdm.h

@@ -356,7 +356,6 @@ typedef enum {
 		"PROGRESS_MEDIA", "ALARM_TRAP", "ALARM_CLEAR", \
 		"COLLECTED_DIGIT", "ADD_CALL", "RESTART", "SIGSTATUS_CHANGED", "COLLISION", "FACILITY", \
 		"TRACE", "TRACE_RAW", "INDICATION_COMPLETED", "INVALID"
-
 /*! \brief Move from string to ftdm_signal_event_t and viceversa */
 FTDM_STR2ENUM_P(ftdm_str2ftdm_signal_event, ftdm_signal_event2str, ftdm_signal_event_t)
 
@@ -653,7 +652,20 @@ typedef ftdm_status_t (*fio_span_get_sig_status_t) FIO_SPAN_GET_SIG_STATUS_ARGS;
 typedef ftdm_status_t (*fio_span_poll_event_t) FIO_SPAN_POLL_EVENT_ARGS ;
 typedef ftdm_status_t (*fio_span_next_event_t) FIO_SPAN_NEXT_EVENT_ARGS ;
 typedef ftdm_status_t (*fio_channel_next_event_t) FIO_CHANNEL_NEXT_EVENT_ARGS ;
+
+/*! \brief Callback for signal delivery (FTDM_SIGEVENT_START and friends) 
+ *  \note This callback is provided by the user during ftdm_configure_span_signaling
+ *
+ *  \note You must NOT do any blocking during this callback since this function is
+ *        most likely called in an internal signaling thread that can potentially be
+ *        shared for all the channels in a span and blocking will delay processing
+ *        (sometimes even audio processing) for other channels
+ *
+ *  \note Although some simple FreeTDM APIs can work (ie: ftdm_span_get_id etc), the
+ *        use of any FreeTDM call API (ie ftdm_channel_call_answer) is discouraged
+ */
 typedef ftdm_status_t (*fio_signal_cb_t) FIO_SIGNAL_CB_ARGS ;
+
 typedef ftdm_status_t (*fio_event_cb_t) FIO_EVENT_CB_ARGS ;
 typedef ftdm_status_t (*fio_configure_span_t) FIO_CONFIGURE_SPAN_ARGS ;
 typedef ftdm_status_t (*fio_configure_t) FIO_CONFIGURE_ARGS ;

libs/freetdm/src/include/private/ftdm_core.h

@@ -500,15 +500,15 @@ struct ftdm_span {
 	ftdm_span_stop_t stop;
 	ftdm_channel_sig_read_t sig_read;
 	ftdm_channel_sig_write_t sig_write;
-	/* Private I/O data per span. Do not touch unless you are an I/O module */
-	void *io_data;
+	ftdm_channel_state_processor_t state_processor; /*!< This guy is called whenever state processing is required */
+	void *io_data; /*!< Private I/O data per span. Do not touch unless you are an I/O module */
 	char *type;
 	char *dtmf_hangup;
 	size_t dtmf_hangup_len;
 	ftdm_state_map_t *state_map;
 	ftdm_caller_data_t default_caller_data;
-	ftdm_queue_t *pendingchans;
-	ftdm_queue_t *pendingsignals;
+	ftdm_queue_t *pendingchans; /*!< Channels pending of state processing */
+	ftdm_queue_t *pendingsignals; /*!< Signals pending from being delivered to the user */
 	struct ftdm_span *next;
 };
 

libs/freetdm/src/include/private/ftdm_state.h

@@ -86,15 +86,21 @@ typedef struct {
 	const char *file;
 	const char *func;
 	int line;
-	ftdm_channel_state_t state;
-	ftdm_channel_state_t last_state;
-	ftdm_time_t time;
-	ftdm_time_t end_time;
+	ftdm_channel_state_t state; /*!< Current state (processed or not) */
+	ftdm_channel_state_t last_state; /*!< Previous state */
+	ftdm_time_t time; /*!< Time the state was set */
+	ftdm_time_t end_time; /*!< Time the state processing was completed */
 } ftdm_state_history_entry_t;
 
 typedef ftdm_status_t (*ftdm_channel_state_processor_t)(ftdm_channel_t *fchan);
 
-FT_DECLARE(ftdm_status_t) ftdm_channel_advance_states(ftdm_channel_t *fchan, ftdm_channel_state_processor_t processor);
+/*!
+ * \brief Process channel states by invoking the channel state processing routine
+ *        it will keep calling the processing routine while the state status
+ *        is FTDM_STATE_STATUS_NEW, it will not do anything otherwise
+ */
+FT_DECLARE(ftdm_status_t) ftdm_channel_advance_states(ftdm_channel_t *fchan);
+
 FT_DECLARE(ftdm_status_t) _ftdm_channel_complete_state(const char *file, const char *function, int line, ftdm_channel_t *fchan);
 #define ftdm_channel_complete_state(obj) _ftdm_channel_complete_state(__FILE__, __FUNCTION__, __LINE__, obj)
 FT_DECLARE(int) ftdm_check_state_all(ftdm_span_t *span, ftdm_channel_state_t state);
@@ -171,16 +177,26 @@ struct ftdm_state_map {
 };
 typedef struct ftdm_state_map ftdm_state_map_t;
 
+/*!\brief Set the state for a channel (the channel must be locked when calling this function)
+ * \note Signaling modules should use ftdm_set_state macro instead
+ * \note If this function is called with the wait parameter set to a non-zero value, the recursivity
+ *       of the channel lock must be == 1 because the channel will be unlocked/locked when waiting */
 FT_DECLARE(ftdm_status_t) ftdm_channel_set_state(const char *file, const char *func, int line,
 		ftdm_channel_t *ftdmchan, ftdm_channel_state_t state, int wait);
 
-/*!\brief Set the state of a channel immediately and implicitly complete the previous state */
+/*!\brief Set the state of a channel immediately and implicitly complete the previous state if needed 
+ * \note FTDM_SIGEVENT_INDICATION_COMPLETED will be sent if the state change 
+ *       is associated to some indication (ie FTDM_CHANNEL_INDICATE_PROCEED)
+ * \note The channel must be locked when calling this function
+ * */
 FT_DECLARE(ftdm_status_t) _ftdm_set_state(const char *file, const char *func, int line,
 			ftdm_channel_t *fchan, ftdm_channel_state_t state);
 #define ftdm_set_state(obj, s) _ftdm_set_state(__FILE__, __FUNCTION__, __LINE__, obj, s);									\
 
 /*!\brief This macro is deprecated, signaling modules should always lock the channel themselves anyways since they must
  * process first the user pending state changes then set a new state before releasing the lock 
+ * this macro is here for backwards compatibility, DO NOT USE IT in new code since it is *always* wrong to set
+ * a state in a signaling module without checking and processing the current state first (and for that you must lock the channel)
  */
 #define ftdm_set_state_locked(obj, s) \
 	do { \