rejoice! tasks suck no more

1 files changed, 48 insertions, 54 deletions

diff --git a/src/task.c b/src/task.c
index b290e3c..13e4e75 100644
--- a/src/task.c
+++ b/src/task.c
@@ -3,77 +3,78 @@
 #include <stm32l476xx.h>
 
 typedef struct {
-	uint32_t *sp;
-	uint8_t use;
+	void *next;
 	uint32_t *stack;
-	void (*code)(void);
+	uint32_t *sp;
 } task_t;
 
-#define MAX_TASKS	6
+static task_t *current;
+static uint8_t task_disable = 0;
 
-static task_t tasks[MAX_TASKS];
-static volatile int next_idx = 0;
+void task_hold(uint8_t hold)
+{
+	if (hold != 0)
+		task_disable++;
+	else if (task_disable > 0)
+		task_disable--;
+}
 
-static uint8_t task_enable = 0;
+void task_exit(void)
+{
+	// TODO free stack?
+	// TODO remove from chain
+	// hopefully current is preserved..?
+	while (1); // bye
+}
 
-void task_hold(uint8_t hold)
+task_t *task_create(void (*code)(void), uint32_t stackSize)
 {
-	task_enable = !hold;
+	task_t *t = (task_t *)malloc(sizeof(task_t));
+	t->next = 0;
+	t->stack = (uint32_t *)malloc(stackSize);
+	t->sp = (void *)t->stack + stackSize - 64;//16;
+	t->sp[13] = (uint32_t)task_exit;
+	t->sp[14] = (uint32_t)code;
+	t->sp[15] = 0x01000000;
+	return t;
 }
 
 void task_init(void (*init)(void))
 {
-	for (int i = 0; i < MAX_TASKS; i++)
-		tasks[i].use = 0;
-
-	task_start(init, 4096);
+	current = task_create(init, 4096);
+	current->next = current;
+	// bit 0 - priv, bit 1 - psp/msp
 	asm("\
 		msr psp, %0; \
 		mrs r0, control; \
-		orr r0, r0, #3; \
+		orr r0, r0, #2; \
 		msr control, r0; \
 		isb; \
-	" :: "r" (tasks[0].sp));
+	" :: "r" (current->sp));
 
-	task_enable = 1;
+	task_disable = 0;
 	init();
-}
-
-extern void _exit(int);
-void task_exit(void)
-{
-	// TODO free stack?
-	asm("cpsid i"); // hope to catch next_idx
-	tasks[next_idx].use = 0;
-	asm("cpsie i");
-	while (1); // bye
+	// you dirty dirty dog
+	/*asm("\
+		cpsie i; \
+		mov pc, %0; \
+	" :: "r" (init + 4));*/
 }
 
 void task_start(void (*task)(void), uint16_t stackSize)
 {
-	asm("cpsid i"); // just to be safe
-
-	for (int i = 0; i < MAX_TASKS; i++) {
-		if (tasks[i].use == 0) {
-			tasks[i].stack = malloc(stackSize);
-			tasks[i].sp = tasks[i].stack + stackSize - 16;
-			tasks[i].sp[13] = (uint32_t)task_exit;
-			tasks[i].sp[14] = (uint32_t)task;
-			tasks[i].sp[15] = 0x01000000;
-			tasks[i].use = 1;
-			tasks[i].code = task;
-			asm("cpsie i");
-			return;
-		}
-	}
-
-	// TODO handle error
+	task_hold(1);
+	task_t *t = task_create(task, stackSize);
+	task_t *next = (task_t *)current->next;
+	current->next = t;
+	t->next = next;
+	task_hold(0);
 }
 
 __attribute__ ((naked))
 void PendSV_Handler(void) 
 {
-	if (task_enable == 0)
+	if (task_disable != 0)
 		asm("bx lr");
 
 	// save state
@@ -84,15 +85,9 @@ void PendSV_Handler(void)
 		mrs r0, psp; \
 		stmdb r0!, {r4-r11}; \
 		mov %0, r0; \
-	" : "=r" (tasks[next_idx].sp));
+	" : "=r" (current->sp));
 
-	// find next task (round-robin style)
-	do {
-		if (++next_idx == MAX_TASKS) {
-			next_idx = 0;
-			break; // task 0 better exist
-		}
-	} while (tasks[next_idx].use == 0);
+	current = current->next;
 
 	// restore
 	asm("\
@@ -101,11 +96,10 @@ void PendSV_Handler(void)
 		msr psp, r0; \
 		isb; \
 		dsb; \
-	" :: "r" (tasks[next_idx].sp));
+	" :: "r" (current->sp));
 
 	// end
 	asm("\
-		mov r0, #0xFFFFFFFD; \
 		cpsie i; \
 		bx lr; \
 	");