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/*
* Copyright © 2009 Keith Packard <keithp@keithp.com>
*
* 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; version 2 of the License.
*
* 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.
*/
#include "ao.h"
#define AO_NO_TASK 0xff
__xdata struct ao_task * __xdata ao_tasks[AO_NUM_TASKS];
__data uint8_t ao_num_tasks;
__data uint8_t ao_cur_task_id;
__xdata struct ao_task *__data ao_cur_task;
void
ao_add_task(__xdata struct ao_task * task, void (*start)(void))
{
uint8_t __xdata *stack;
if (ao_num_tasks == AO_NUM_TASKS)
ao_panic(AO_PANIC_NO_TASK);
ao_tasks[ao_num_tasks++] = task;
/*
* Construct a stack frame so that it will 'return'
* to the start of the task
*/
stack = task->stack;
*stack++ = ((uint16_t) start);
*stack++ = ((uint16_t) start) >> 8;
/* and the stuff saved by ao_switch */
*stack++ = 0; /* acc */
*stack++ = 0x80; /* IE */
*stack++ = 0; /* DPL */
*stack++ = 0; /* DPH */
*stack++ = 0; /* B */
*stack++ = 0; /* R2 */
*stack++ = 0; /* R3 */
*stack++ = 0; /* R4 */
*stack++ = 0; /* R5 */
*stack++ = 0; /* R6 */
*stack++ = 0; /* R7 */
*stack++ = 0; /* R0 */
*stack++ = 0; /* R1 */
*stack++ = 0; /* PSW */
*stack++ = 0; /* BP */
task->stack_count = stack - task->stack;
task->wchan = NULL;
}
/* Task switching function. This must not use any stack variables */
void
ao_yield(void) _naked
{
static uint8_t __data stack_len;
static __data uint8_t * __data stack_ptr;
static __xdata uint8_t * __data save_ptr;
/* Save current context */
_asm
/* Push ACC first, as when restoring the context it must be restored
* last (it is used to set the IE register). */
push ACC
/* Store the IE register then enable interrupts. */
push _IEN0
setb _EA
push DPL
push DPH
push b
push ar2
push ar3
push ar4
push ar5
push ar6
push ar7
push ar0
push ar1
push PSW
_endasm;
PSW = 0;
_asm
push _bp
_endasm;
if (ao_cur_task_id != AO_NO_TASK)
{
/* Save the current stack */
stack_len = SP - (AO_STACK_START - 1);
ao_cur_task->stack_count = stack_len;
stack_ptr = (uint8_t __data *) AO_STACK_START;
save_ptr = (uint8_t __xdata *) ao_cur_task->stack;
while (stack_len--)
*save_ptr++ = *stack_ptr++;
}
/* Empty the stack; might as well let interrupts have the whole thing */
SP = AO_STACK_START - 1;
/* Find a task to run. If there isn't any runnable task,
* this loop will run forever, which is just fine
*/
for (;;) {
++ao_cur_task_id;
if (ao_cur_task_id == ao_num_tasks)
ao_cur_task_id = 0;
ao_cur_task = ao_tasks[ao_cur_task_id];
if (ao_cur_task->wchan == NULL)
break;
}
/* Restore the old stack */
stack_len = ao_cur_task->stack_count;
SP = AO_STACK_START - 1 + stack_len;
stack_ptr = (uint8_t __data *) AO_STACK_START;
save_ptr = (uint8_t __xdata *) ao_cur_task->stack;
while (stack_len--)
*stack_ptr++ = *save_ptr++;
_asm
pop _bp
pop PSW
pop ar1
pop ar0
pop ar7
pop ar6
pop ar5
pop ar4
pop ar3
pop ar2
pop b
pop DPH
pop DPL
/* The next byte of the stack is the IE register. Only the global
enable bit forms part of the task context. Pop off the IE then set
the global enable bit to match that of the stored IE register. */
pop ACC
JB ACC.7,0098$
CLR _EA
LJMP 0099$
0098$:
SETB _EA
0099$:
/* Finally pop off the ACC, which was the first register saved. */
pop ACC
ret
_endasm;
}
int
ao_sleep(__xdata void *wchan)
{
__critical {
ao_cur_task->wchan = wchan;
}
ao_yield();
}
int
ao_wakeup(__xdata void *wchan)
{
uint8_t i;
for (i = 0; i < ao_num_tasks; i++)
if (ao_tasks[i]->wchan == wchan)
ao_tasks[i]->wchan = NULL;
}
void
ao_start_scheduler(void)
{
ao_cur_task_id = AO_NO_TASK;
ao_cur_task = NULL;
ao_yield();
}
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