/* =================================================================
 * This simple program tests the scheduler to see if the execution 
 * times for the task are uniform. 
 *
 * Test the RTAI scheduler.  Before running this module, you
 * must install rtai and rtai_sched.
 *
 * =================================================================
 */

#include <linux/module.h>
#include <asm/io.h>
#include <math.h>
#include <rtai.h>
#include <rtai_sched.h>

#define TICK_PERIOD   5000000000    // 5 seconds in nanoseconds
#define STACK_SIZE    1000 
#define TASK_PRIORITY 1 

static RT_TASK  rt_task;

static void printTime (int val)
{
   RTIME    t;
   long     time;
   long     last_time;
   long     interval;
   

   // Initialize the last time.

   last_time = 0l; 

   while (1)
   {
      /*
       * Get the time and print the interval time.
       * rt_get_time_ns gets the time since the timer started in nanoseconds
       *
       * printk is the module form of printf.  Output goes through the kernel
       * output process and can be read with the command dmesg.
       */

      t = (long) rt_get_time_ns ();
      // time = (int) t * 0.000001; // (t / 1000000 + 0.5);
      interval = t - last_time;
      printk ("Interval = %ld, error = %ld\n", interval, 
         interval - TICK_PERIOD);
      last_time = t;

      /* 
       * That was fun, lets do it again.
       * rt_task_wait_period suspends this task until the next period is
       * reached.
       */

      rt_task_wait_period ();
   }
}

int init_module (void)
{
    RTIME  tick_period;

    /* 
     * Set the mode to periodic and create a task
     * rt_task_init creates a task
     *    task structure to save task data
     *    the thread to execute when the task runs; this task must
     *        have the calling sequence void f (int).
     *    the data to pass to the newly created task - a single int
     *    the stack size - STACK_SIZE is the default size constant
     *    the task priority, 0 is highest, RT_LOWEST_PRIORITY is lowest
     *    a flag indicating if the floating point unit will be used
     *    the 
     *    a function to be called when the task become the current running
     *       task after a context switch.
     *
     * rt_set_periodic_mode sets the periodic mode for the system timer;
     *    the alternative is rt_set_oneshot_mode for a single interrupt
     *    and then the task must be rescheduled.
     */


    rt_set_periodic_mode ();
    rt_task_init (&rt_task, printTime, 1, STACK_SIZE, TASK_PRIORITY, 0, 0);

    /* 
     * Set up a tick period and start the periodic scheduling.
     * 
     * start_rt_timer starts the timer with the given period.  nano2count
     * converts the time in nanoseconds to the internal clock representation.
     *
     * rt_task_make_periodic makes the task periodic with the parameters:
     *   the task to schedule periodically
     *   the time at which to start periodic scheduling; rt_get_time
     *      gets that to the current time.
     *   the period
     */


    
    tick_period = start_rt_timer (nano2count (TICK_PERIOD));
    rt_task_make_periodic (&rt_task, rt_get_time () + tick_period, tick_period);

    return 0;
}

void cleanup_module (void)
{
    /*
     * Stop the timer and dispose of the task.
     */

    stop_rt_timer ();
    rt_task_delete (&rt_task);
    
    return;
}