From 99a7eccbe48e6f9cff9711ba98b5ddde6bdd9ee4 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Sun, 25 Jun 2023 21:00:14 -0300
Subject: [PATCH] kernel: DPC support

---
 kernel-src/arch/x86-64/main.c         |  2 +
 kernel-src/include/kernel/dpc.h       | 22 ++++++++
 kernel-src/include/kernel/interrupt.h |  1 +
 kernel-src/include/x86-64/arch/cpu.h  |  2 +
 kernel-src/sys/dpc.c                  | 74 +++++++++++++++++++++++++++
 5 files changed, 101 insertions(+)
 create mode 100644 kernel-src/include/kernel/dpc.h
 create mode 100644 kernel-src/sys/dpc.c

diff --git a/kernel-src/arch/x86-64/main.c b/kernel-src/arch/x86-64/main.c
index 61faf688..9d02984a 100644
--- a/kernel-src/arch/x86-64/main.c
+++ b/kernel-src/arch/x86-64/main.c
@@ -22,6 +22,7 @@
 #include <arch/ps2.h>
 #include <kernel/keyboard.h>
 #include <kernel/console.h>
+#include <kernel/dpc.h>
 
 static cpu_t bsp_cpu;
 
@@ -31,6 +32,7 @@ void kernel_entry() {
 	arch_gdt_reload();
 	arch_idt_setup();
 	arch_idt_reload();
+	dpc_init();
 	pmm_init();
 	term_init();
 	logging_sethook(term_putchar);
diff --git a/kernel-src/include/kernel/dpc.h b/kernel-src/include/kernel/dpc.h
new file mode 100644
index 00000000..a7e6a879
--- /dev/null
+++ b/kernel-src/include/kernel/dpc.h
@@ -0,0 +1,22 @@
+#ifndef _DPC_H
+#define _DPC_H
+
+#include <arch/context.h>
+#include <stdbool.h>
+
+typedef void * dpcarg_t;
+typedef void (*dpcfn_t)(context_t *, dpcarg_t);
+
+typedef struct _dpc_t {
+	struct _dpc_t *next;
+	struct _dpc_t *prev;
+	bool enqueued;
+	dpcfn_t fn;
+	dpcarg_t arg;
+} dpc_t;
+
+void dpc_enqueue(dpc_t *dpc, dpcfn_t, dpcarg_t);
+void dpc_dequeue(dpc_t *dpc);
+void dpc_init();
+
+#endif
diff --git a/kernel-src/include/kernel/interrupt.h b/kernel-src/include/kernel/interrupt.h
index 12f90221..6cb837e7 100644
--- a/kernel-src/include/kernel/interrupt.h
+++ b/kernel-src/include/kernel/interrupt.h
@@ -15,6 +15,7 @@
 #define IPL_MAX 0
 #define IPL_TIMER 1
 #define IPL_KEYBOARD 2
+#define IPL_DPC 900
 #define IPL_NORMAL 1000
 
 struct _isr_t;
diff --git a/kernel-src/include/x86-64/arch/cpu.h b/kernel-src/include/x86-64/arch/cpu.h
index 27b24a70..a0ff6755 100644
--- a/kernel-src/include/x86-64/arch/cpu.h
+++ b/kernel-src/include/x86-64/arch/cpu.h
@@ -10,6 +10,7 @@
 #include <kernel/vmm.h>
 #include <kernel/timer.h>
 #include <kernel/scheduler.h>
+#include <kernel/dpc.h>
 
 typedef struct cpu_t {
 	thread_t *thread;
@@ -26,6 +27,7 @@ typedef struct cpu_t {
 	timerentry_t schedtimerentry;
 	void *schedulerstack;
 	isr_t *isrqueue;
+	dpc_t *dpcqueue;
 } cpu_t;
 
 #define CPU_HALT() asm volatile("hlt")
diff --git a/kernel-src/sys/dpc.c b/kernel-src/sys/dpc.c
new file mode 100644
index 00000000..77ef5f38
--- /dev/null
+++ b/kernel-src/sys/dpc.c
@@ -0,0 +1,74 @@
+#include <kernel/dpc.h>
+#include <arch/cpu.h>
+#include <kernel/interrupt.h>
+#include <logging.h>
+
+static isr_t *dpcisr;
+
+static void remove(dpc_t *dpc) {
+	if (dpc->prev)
+		dpc->prev->next = dpc->next;
+	else 
+		_cpu()->dpcqueue = dpc->next;
+
+	if (dpc->next)
+		dpc->next->prev = dpc->prev;
+}
+
+static void insert(dpc_t *dpc) {
+	dpc->prev = NULL;
+	dpc->next = _cpu()->dpcqueue;
+
+	if (dpc->next)
+		dpc->next->prev = dpc;
+
+	_cpu()->dpcqueue = dpc;
+}
+
+static void isrfn(isr_t *self, context_t *context) {
+	while (_cpu()->dpcqueue) {
+		dpc_t *dpc = _cpu()->dpcqueue;
+		remove(dpc);
+
+		__assert(dpc->enqueued);
+		dpc->enqueued = false;
+
+		interrupt_set(true);
+		dpc->fn(context, dpc->arg);
+		interrupt_set(false);
+	}
+}
+
+void dpc_enqueue(dpc_t *dpc, dpcfn_t fn, dpcarg_t arg) {
+	bool entrystate = interrupt_set(false);
+
+	if (dpc->enqueued)
+		goto cleanup;
+
+	dpc->fn = fn;
+	dpc->arg = arg;
+	dpc->enqueued = true;
+	insert(dpc);
+	interrupt_raise(dpcisr);
+
+	cleanup:
+	interrupt_set(entrystate);
+}
+
+void dpc_dequeue(dpc_t *dpc) {
+	bool entrystate = interrupt_set(false);
+
+	if (dpc->enqueued == false)
+		goto cleanup;
+
+	dpc->enqueued = false;
+	remove(dpc);
+
+	cleanup:
+	interrupt_set(entrystate);
+}
+
+void dpc_init() {
+	dpcisr = interrupt_allocate(isrfn, NULL, IPL_DPC);
+	__assert(dpcisr);
+}