add gsm_timers, for Tnnn definitions usable by FSMs

Change-Id: If212fcd042051b6fa53484254223614c5b93a9c6
diff --git a/include/osmocom/bsc/gsm_timers.h b/include/osmocom/bsc/gsm_timers.h
new file mode 100644
index 0000000..fde8c93
--- /dev/null
+++ b/include/osmocom/bsc/gsm_timers.h
@@ -0,0 +1,55 @@
+/* API to define Tnnn timers globally, configure in VTY and use for FSM state changes. */
+#pragma once
+
+#include <stdint.h>
+#include <osmocom/core/utils.h>
+
+struct osmo_fsm_inst;
+struct vty;
+
+enum T_unit {
+	T_S = 0,	/*< most T are in seconds, keep 0 as default. */
+	T_MS,		/*< milliseconds */
+	T_M,		/*< minutes */
+	T_CUSTOM,
+};
+
+extern const struct value_string T_unit_names[];
+static inline const char *T_unit_name(enum T_unit val)
+{ return get_value_string(T_unit_names, val); }
+
+/* Define a GSM timer of the form Tnnn, with unit, default value and doc string. */
+struct T_def {
+	const int T; /*< T1234 number */
+	const int default_val; /*< timeout duration (according to unit), default value. */
+	const enum T_unit unit;
+	const char *desc;
+	int val; /*< currently active value, e.g. set by user config. */
+};
+
+/* Iterate an array of struct T_def, the last item should be fully zero, i.e. "{}" */
+#define for_each_T_def(d, T_defs) \
+	for (d = T_defs; d && (d->T || d->default_val || d->desc); d++)
+
+int T_def_get(struct T_def *T_defs, int T, enum T_unit as_unit, int val_if_not_present);
+void T_defs_reset(struct T_def *T_defs);
+struct T_def *T_def_get_entry(struct T_def *T_defs, int T);
+
+void T_defs_vty_init(struct T_def *T_defs, int cfg_parent_node);
+void T_defs_vty_write(struct vty *vty, const char *indent);
+
+
+struct state_timeout {
+	int T;
+	bool keep_timer;
+};
+
+struct state_timeout *get_state_timeout(uint32_t state, struct state_timeout *timeouts_array);
+
+#define fsm_inst_state_chg_T(fi, state, timeouts_array, T_defs, default_timeout) \
+	_fsm_inst_state_chg_T(fi, state, timeouts_array, T_defs, default_timeout, \
+			      __FILE__, __LINE__)
+int _fsm_inst_state_chg_T(struct osmo_fsm_inst *fi, uint32_t state,
+			  struct state_timeout *timeouts_array,
+			  struct T_def *T_defs, int default_timeout,
+			  const char *file, int line);