kernel.h

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/**
 * @file   kernel.h
 *
 * @brief kernel data structures used in os.c.
 *
 * CSC 460/560 Real Time Operating Systems - Mantis Cheng
 *
 * @author Scott Craig
 * @author Justin Tanner
 */
#ifndef __KERNEL_H__
#define __KERNEL_H__

#include <avr/io.h>
#include "os.h"

/** Disable default prescaler to make processor speed 8 MHz. */
#define CLOCK8MHZ()    CLKPR = (1<<CLKPCE); CLKPR = 0x00;

#define F_CPU 8000000UL

#define Disable_Interrupt()     asm volatile ("cli"::)
#define Enable_Interrupt()     asm volatile ("sei"::)

/** The maximum number of names. Currently the same as the number of tasks. */
#define     MAXNAME     MAXPROCESS

/** The number of clock cycles in one "tick" or 5 ms */
#define TICK_CYCLES     (F_CPU / 1000 * TICK)

/** LEDs for OS_Abort() */
#define LED_RED_MASK    (uint8_t)(_BV(4) | _BV(7))

/** LEDs for OS_Abort() */
#define LED_GREEN_MASK    (uint8_t)(_BV(5) | _BV(6))


/* Typedefs and data structures. */

typedef void (*voidfuncvoid_ptr) (void);      /* pointer to void f(void) */

/**
 * @brief This is the set of states that a task can be in at any given time.
 */
typedef enum
{
    DEAD = 0,
    RUNNING,
    READY,
    WAITING
}
task_state_t;

/**
 * @brief This is the set of kernel requests, i.e., a request code for each system call.
 */
typedef enum
{
    NONE = 0,
    TIMER_EXPIRED,
    TASK_CREATE,
    TASK_TERMINATE,
    TASK_NEXT,
    TASK_GET_ARG,
    EVENT_INIT,
    EVENT_WAIT,
    EVENT_SIGNAL,
    EVENT_BROADCAST,
    EVENT_SIGNAL_AND_NEXT,
    EVENT_BROADCAST_AND_NEXT
}
kernel_request_t;


/**
 * @brief The arguments required to create a task.
 */
typedef struct
{
    /** The code the new task is to run.*/
    voidfuncvoid_ptr f;
    /** A new task may be created with an argument that it can retrieve later. */
    int arg;
    /** Priority of the new task: RR, PERIODIC, SYSTEM */
    uint8_t level;
    /** If the new task is PERIODIC, this is its name in the PPP array. */
    uint8_t name;
}
create_args_t;


typedef struct td_struct task_descriptor_t;
/**
 * @brief All the data needed to describe the task, including its context.
 */
struct td_struct
{
    /** The stack used by the task. SP points in here when task is RUNNING. */
    uint8_t                         stack[WORKSPACE];
    /** A variable to save the hardware SP into when the task is suspended. */
    uint8_t*               volatile sp;   /* stack pointer into the "workSpace" */
    /** PERIODIC tasks need a name in the PPP array. */
    uint8_t                         name;
    /** The state of the task in this descriptor. */
    task_state_t                    state;
    /** The argument passed to Task_Create for this task. */
    int                             arg;
    /** The priority (type) of this task. */
    uint8_t                         level;
    /** A link to the next task descriptor in the queue holding this task. */
    task_descriptor_t*              next;
};


/**
 * @brief Contains pointers to head and tail of a linked list.
 */
typedef struct
{
    /** The first item in the queue. NULL if the queue is empty. */
    task_descriptor_t*  head;
    /** The last item in the queue. Undefined if the queue is empty. */
    task_descriptor_t*  tail;
}
queue_t;


#endif

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