From f8788720f5b458d57f9b58d8c9e053d4ec190b68 Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Mon, 20 Apr 2020 19:19:14 +0200
Subject: [PATCH] Implement int 28h: Idle callout

---
 boot/kernel.asm | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/boot/kernel.asm b/boot/kernel.asm
index 7c94c61..a31d9a3 100644
--- a/boot/kernel.asm
+++ b/boot/kernel.asm
@@ -204,6 +204,15 @@ ldbpb:	push ds
 	pop ds
 	ret
 
+	; DOS 2+ - DOS IDLE INTERRUPT
+	; Usually hooked by TSRs
+idle:	sti
+	; sti takes one instruction to take effect
+	nop
+	; Wait until next interrupt
+	hlt
+	iret
+
 	; DOS 2+ - FAST CONSOLE OUTPUT
 	; IN	al	character to print
 fputc:	push ax
@@ -215,7 +224,7 @@ fputc:	push ax
 	pop ax
 	iret
 
-main:	hlt
+main:	int 0x28
 	jmp main
 
 init:	cli
@@ -253,5 +262,5 @@ init:	cli
 
 ivects:	dw int20h, int21h, iret, iret
 	dw iret, iret, iret, iret
-	dw iret, fputc, iret, iret
+	dw idle, fputc, iret, iret
 	dw iret, iret, iret, iret