From 3413fbd3a84fc839e840bf38e10f1a80ba014147 Mon Sep 17 00:00:00 2001
From: Braiden Vasco <braiden-vasco@users.noreply.github.com>
Date: Mon, 6 Nov 2017 10:57:55 +0000
Subject: [PATCH] Add function "pic_end_of_interrupt"

---
 arch/hwint.c | 11 ++---------
 arch/pic.c   | 31 ++++++++++++++++++++++++++++---
 arch/pic.h   |  2 ++
 3 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/arch/hwint.c b/arch/hwint.c
index 03f207a..e18fd20 100644
--- a/arch/hwint.c
+++ b/arch/hwint.c
@@ -4,6 +4,7 @@
 #include "config.h"
 #include "asm.h"
 #include "logger.h"
+#include "pic.h"
 
 static const char *const messages[] = {
     "Unhandled hardware interrupt: 0",
@@ -35,15 +36,7 @@ void hwint_handler(struct IsrRegisters regs)
         return;
     }
 
-    // Send an EOI (end of interrupt) signal to the PICs
-
-    if (regs.int_no >= 40) { // TODO: hardcoded
-        // Send reset signal to slave
-        outportb(0xA0, 0x20); // TODO: hardcoded
-    }
-
-    // Send reset signal to master
-    outportb(0x20, 0x20); // TODO: hardcoded
+    pic_end_of_interrupt(regs.int_no);
 
     const unsigned char hwint_no = regs.int_no - INT_HWINT_FIRST;
 
diff --git a/arch/pic.c b/arch/pic.c
index 165c6c2..3dfa147 100644
--- a/arch/pic.c
+++ b/arch/pic.c
@@ -9,10 +9,19 @@
 #define SLAVE_COMMAND 0xA0
 #define SLAVE_DATA    0xA1
 
-void pic_remap(const unsigned char master_irq_start, const unsigned char slave_irq_start)
+#define IRQS_COUNT 8
+
+static unsigned char master_irq_start = 0;
+static unsigned char slave_irq_start  = 8;
+
+void pic_remap(const unsigned char new_master_irq_start, const unsigned char new_slave_irq_start)
 {
     logger_info_from("pic", "Remap the IRQ table.");
 
+    // Remember IRQ numbers
+    master_irq_start = new_master_irq_start;
+    slave_irq_start  = new_slave_irq_start;
+
     // Save masks
     unsigned char master_mask = inportb(MASTER_DATA);
     unsigned char slave_mask  = inportb(SLAVE_DATA);
@@ -22,8 +31,8 @@ void pic_remap(const unsigned char master_irq_start, const unsigned char slave_i
     outportb(SLAVE_COMMAND,  0x11);
 
     // Set IRQ vectors
-    outportb(MASTER_DATA, master_irq_start);
-    outportb(SLAVE_DATA,  slave_irq_start);
+    outportb(MASTER_DATA, new_master_irq_start);
+    outportb(SLAVE_DATA,  new_slave_irq_start);
 
     // Connect master and slave with each other
     outportb(MASTER_DATA, 0x04);
@@ -37,3 +46,19 @@ void pic_remap(const unsigned char master_irq_start, const unsigned char slave_i
     outportb(MASTER_DATA, master_mask);
     outportb(SLAVE_DATA,  slave_mask);
 }
+
+void pic_end_of_interrupt(const unsigned char irq)
+{
+    const unsigned char to_master = master_irq_start <= irq && irq < master_irq_start + IRQS_COUNT;
+    const unsigned char to_slave  = slave_irq_start  <= irq && irq < slave_irq_start  + IRQS_COUNT;
+
+    if (!(to_master || to_slave)) {
+        return;
+    }
+
+    if (to_slave) {
+        outportb(SLAVE_COMMAND, 0x20);
+    }
+
+    outportb(MASTER_COMMAND, 0x20);
+}
diff --git a/arch/pic.h b/arch/pic.h
index c1caa68..11f5238 100644
--- a/arch/pic.h
+++ b/arch/pic.h
@@ -3,4 +3,6 @@
 
 void pic_remap(unsigned char master_irq_start, unsigned char slave_irq_start);
 
+void pic_end_of_interrupt(unsigned char irq);
+
 #endif