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+/* Copyright (C) 2004 David Decotigny
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; either version 2
+   of the License, or (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+   USA. 
+*/
+#ifndef _SOS_TIME_H_
+#define _SOS_TIME_H_
+
+/**
+ * @file time.h
+ *
+ * Primitives and callbacks related to kernel time management (timer
+ * IRQ)
+ */
+
+#include <sos/types.h>
+#include <sos/errno.h>
+#include <sos/klibc.h>
+
+
+/* =======================================================================
+ * Library of time manipulation functions
+ */
+struct sos_time
+{
+  sos_ui32_t sec;
+  sos_ui32_t nanosec;
+};
+
+sos_ret_t sos_time_inc(struct sos_time *dest,
+		       const struct sos_time *to_add);
+
+sos_ret_t sos_time_dec(struct sos_time *dest,
+		       const struct sos_time *to_dec);
+
+int sos_time_cmp(const struct sos_time *t1,
+		 const struct sos_time *t2);
+
+sos_bool_t sos_time_is_zero(const struct sos_time *tm);
+
+
+
+/* =======================================================================
+ * Kernel time management. This is not the same as the "system-time",
+ * ie it does not not take into account the system-time adjustments
+ * (NTP, daylight saving times, etc...): this is the job of a
+ * system-time subsystem.
+ */
+
+
+/**
+ * Initialize kernel time subsystem.
+ *
+ * @param initial_resolution The initial time resolution. MUST be
+ * consistent with that of the hardware timer
+ */
+sos_ret_t sos_time_subsysem_setup(const struct sos_time *initial_resolution);
+
+
+/**
+ * Value of the interval between 2 time ticks. Should be consistent
+ * with the configuration of the hardware timer.
+ */
+sos_ret_t sos_time_get_tick_resolution(struct sos_time *resolution);
+
+
+/**
+ * Change the value of the interval between 2 time ticks. Must be
+ * called each time the hardware timer is reconfigured.
+ *
+ * @note MUST be consistent with that of the hardware timer
+ */
+sos_ret_t sos_time_set_tick_resolution(const struct sos_time *resolution);
+
+
+/**
+ * Get the time elapsed since system boot. Does not take into account
+ * the system-time adjustment (NTP, daylight saving times, etc...):
+ * this is the job of a system-time subsystem.
+ */
+sos_ret_t sos_time_get_now(struct sos_time *now);
+
+
+
+/* =======================================================================
+ * Routines to schedule future execution of routines: "timeout" actions
+ */
+
+/* Forward declaration */
+struct sos_timeout_action;
+
+/**
+ * Prototype of a timeout routine. Called with IRQ disabled !
+ */
+typedef void (sos_timeout_routine_t)(struct sos_timeout_action *);
+
+
+/**
+ * The structure of a timeout action. This structure should have been
+ * opaque to the other parts of the kernel. We keep it public here so
+ * that struct sos_timeout_action can be allocated on the stack from
+ * other source files in the kernel. However, all the fields should be
+ * considered read-only for modules others than time.{ch}.
+ *
+ * @note After an action has been allocated (on the stack or kmalloc),
+ * it MUST be initialized with sos_time_init_action below !
+ */
+struct sos_timeout_action
+{
+  /** PUBLIC: Address of the timeout routine */
+  sos_timeout_routine_t *routine;
+
+  /** PUBLIC: (Custom) data available for this routine */
+  void                  *routine_data;
+  
+  /** PUBLIC: 2 meanings:
+   *  - before and while in the timeout list: absolute due date of the
+   *    timeout action
+   *  - once removed from timeout list: the time remaining in the
+   *    initial timeout (might be 0 if timeout expired) at removal
+   *    time
+   */
+  struct sos_time           timeout;
+
+  /** PRIVATE: To chain the timeout actions */
+  struct sos_timeout_action *tmo_prev, *tmo_next;
+};
+
+
+/**
+ * Initialize a timeout action. MUST be called immediately after
+ * (stack or kmalloc) allocation of the action.
+ *
+ * @param ptr_act Pointer to the action to initialize.
+ */
+#define sos_time_init_action(ptr_act) \
+  ({ (ptr_act)->tmo_prev = (ptr_act)->tmo_next = NULL; /* return */ SOS_OK; })
+
+
+/**
+ * Add the given action in the timeout list, so that it will be
+ * triggered after the specified delay RELATIVE to the time when the
+ * function gets called. The action is always inserted in the list.
+ *
+ * @param act The action to be initialized by the function upon
+ * insertion in the timeout list.
+ *
+ * @param delay Delay until the action is fired. If 0, then it is
+ * fired at next timer IRQ. The action will be fired in X ticks, with
+ * X integer and >= delay.
+ *
+ * @param routine The timeout routine to call when the timeout will be
+ * triggered.
+ *
+ * @param routine_data The data available to the routine when it will
+ * be called.
+ *
+ * @note 'act' MUST remain valid until it is either fired or removed
+ * (with sos_time_remove_action)
+ */
+sos_ret_t
+sos_time_register_action_relative(struct sos_timeout_action *act,
+				  const struct sos_time *delay,
+				  sos_timeout_routine_t *routine,
+				  void *routine_data);
+
+
+/**
+ * Add the given action in the timeout list, so that it will be
+ * triggered after the specified ABSOLUTE date (relative to system
+ * boot time). The action is always inserted in the list.
+ *
+ * @param act The action to be initialized by the function upon
+ * insertion in the timeout list.
+ *
+ * @param date Absolute date (relative to system boot time) when the
+ * action will be triggered.
+ *
+ * @param routine The timeout routine to call when the timeout will be
+ * triggered.
+ *
+ * @param routine_data The data available to the routine when it will
+ * be called.
+ *
+ * @note 'act' MUST remain valid until it is either fired or removed
+ * (with sos_time_remove_action)
+ */
+sos_ret_t
+sos_time_register_action_absolute(struct sos_timeout_action *act,
+				  const struct sos_time *date,
+				  sos_timeout_routine_t *routine,
+				  void *routine_data);
+
+
+/**
+ * The action is removed and its timeout is updated to reflect the
+ * time remaining.
+ */
+sos_ret_t sos_time_unregister_action(struct sos_timeout_action *act);
+
+
+/**
+ * Timer IRQ callback. Call and remove expired actions from the list.
+ *
+ * @note The use of this function is RESERVED (to timer IRQ)
+ */
+sos_ret_t sos_time_do_tick();
+
+
+#endif /* _SOS_TIME_H_ */