Initial AltOS import

1 files changed, 185 insertions, 0 deletions

diff --git a/ao_task.c b/ao_task.c
new file mode 100644
index 00000000..4f7387e3
--- /dev/null
+++ b/ao_task.c
@@ -0,0 +1,185 @@
+/*
+ * 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; 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.
+ */
+
+#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_ERROR_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 disable interrupts. */
+		push	_IEN0
+		clr	_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;
+		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;
+
+	/* 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;
+	stack_ptr = (uint8_t __data *) AO_STACK_START;
+	save_ptr = (uint8_t __xdata *) ao_cur_task->stack;
+	while (stack_len--)
+		*stack_ptr++ = *save_ptr++;
+	SP = (uint8_t) (stack_ptr - 1);
+
+	_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)
+{
+	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();
+}