From d18e0e332fedde28587e8396a7f3be13c693c313 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Sun, 23 Apr 2023 16:48:58 -0300
Subject: [PATCH] kernel: initial timer abstraction

---
 kernel-src/include/kernel/timer.h | 26 +++++++++++
 kernel-src/sys/timer.c            | 73 +++++++++++++++++++++++++++++++
 2 files changed, 99 insertions(+)
 create mode 100644 kernel-src/include/kernel/timer.h
 create mode 100644 kernel-src/sys/timer.c

diff --git a/kernel-src/include/kernel/timer.h b/kernel-src/include/kernel/timer.h
new file mode 100644
index 00000000..59a833b1
--- /dev/null
+++ b/kernel-src/include/kernel/timer.h
@@ -0,0 +1,26 @@
+#ifndef _TIMER_H
+#define _TIMER_H
+
+#include <time.h>
+#include <arch/context.h>
+
+typedef struct timerentry_t {
+	struct timerentry_t *next;
+	time_t absolutetick;
+	void *private;
+	void (*func)(void *private, context_t* context);
+} timerentry_t;
+
+typedef struct {
+	time_t ticksperus;
+	time_t tickcurrent;
+	void (*arm)(time_t);
+	time_t (*stop)();
+	timerentry_t *queue;
+} timer_t;
+
+void timer_isr(timer_t *timer, context_t *context);
+void timer_insert(timer_t *timer, timerentry_t *entry, time_t us);
+timer_t *timer_new(time_t ticksperus, void (*arm)(time_t), time_t (*stop)());
+
+#endif
diff --git a/kernel-src/sys/timer.c b/kernel-src/sys/timer.c
new file mode 100644
index 00000000..deb7865b
--- /dev/null
+++ b/kernel-src/sys/timer.c
@@ -0,0 +1,73 @@
+#include <kernel/timer.h>
+#include <kernel/alloc.h>
+#include <logging.h>
+#include <kernel/interrupt.h>
+
+void timer_isr(timer_t *timer, context_t *context) {
+	// TODO lock
+	__assert(timer->queue);
+	timer->tickcurrent = timer->queue->absolutetick;
+	timerentry_t *oldentry = timer->queue;
+	timer->queue = timer->queue->next;
+
+	if (timer->queue) {
+		// TODO handle this
+		__assert(timer->queue->absolutetick > timer->tickcurrent);
+		timer->arm(timer->queue->absolutetick - timer->tickcurrent);
+	}
+
+	// TODO unlock
+	oldentry->func(oldentry->private, context);
+}
+
+void timer_insert(timer_t *timer, timerentry_t* entry, time_t us) {
+	long oldipl = interrupt_setipl(IPL_TIMER);
+	// TODO lock
+
+	timer->tickcurrent += timer->stop(timer);
+
+	time_t tickdiff = us * timer->ticksperus;
+	entry->absolutetick = timer->tickcurrent + tickdiff;
+
+	if (timer->queue == NULL) { // if no other entries in the queue
+		entry->next = NULL;
+		timer->queue = entry;
+	}else if (timer->queue->absolutetick > entry->absolutetick) { // if the current entry should be put before all the others in the queue
+		entry->next = timer->queue;
+		timer->queue = entry;
+	} else {
+		timerentry_t *search = timer->queue;
+
+		while(search) {
+			if (search->next == NULL) { // if last entry in the queue
+				entry->next = NULL;
+				search->next = entry;
+				break;
+			} else if (entry->absolutetick >= search->absolutetick && search->next->absolutetick > entry->absolutetick) { // insert between two
+				entry->next = search->next;
+				search->next = entry;
+				break;
+			}
+			search = search->next;
+		}
+	}
+
+	// TODO handle this case properly
+	__assert(timer->queue->absolutetick > timer->tickcurrent);
+	timer->arm(timer->queue->absolutetick - timer->tickcurrent);
+
+	// TODO unlock
+	interrupt_setipl(oldipl);
+}
+
+timer_t *timer_new(time_t ticksperus, void (*arm)(time_t), time_t (*stop)()) {
+	timer_t *timer = alloc(sizeof(timer_t));
+	if (timer == NULL)
+		return NULL;
+
+	timer->ticksperus = ticksperus;
+	timer->arm = arm;
+	timer->stop = stop;
+
+	return timer;
+}