From 404825387b7a5449fb1ab2d1b7188fd66b9a9354 Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Thu, 30 Apr 2020 20:22:14 +0200
Subject: [PATCH] mbr: make use of BPB includes

---
 boot/mbr.asm | 35 ++++++++++++++++-------------------
 1 file changed, 16 insertions(+), 19 deletions(-)

diff --git a/boot/mbr.asm b/boot/mbr.asm
index 5db6217..6655e48 100644
--- a/boot/mbr.asm
+++ b/boot/mbr.asm
@@ -1,19 +1,16 @@
-; FDC fields in VBR
-%define bps	(bs + 0x0B)
-%define md	(bs + 0x15)
-%define spt	(bs + 0x18)
-%define nos	(bs + 0x1A)
-%define po	(bs + 0x1C)
-
-; blah dont judge me, i miss 8080
-%macro retnz 0
-	jz short ($+3)
+	; blah dont judge me, i miss 8080
+	%macro retnz 0
+	jz short ($+2+1)
 	ret
-%endmacro
-%macro callc 1
-	jnc short ($+5)
+	%endmacro
+	%macro callc 1
+	jnc short ($+2+3)
 	call %1
-%endmacro
+	%endmacro
+
+	%include "inc/bpb.asm"
+
+	%define bpb	bs+0x0B
 
 	cpu 8086
 	org 0x0600
@@ -75,11 +72,11 @@ main:	; find active partition
 
 	; FAT bpb has "bytes per sector" at this place
 	; we support only 512 byte sectors anyways
-	cmp word [bps], 512
+	cmp word [bpb+bpb_ss], 512
 	jne chain
 
 	; Media descriptor byte is never smaller than 0xF0
-	cmp byte [md], 0xF0
+	cmp byte [bpb+bpb_md], 0xF0
 	jc chain
 
 	; ask BIOS what our disk geometry is
@@ -95,17 +92,17 @@ main:	; find active partition
 	; update sectors per track
 	xor ax, ax
 	mov al, cl
-	mov [spt], ax
+	mov [bpb+bpb_spt], ax
 
 	; update number of sides
 	xor ax, ax
 	mov al, dh
-	mov [nos], ax
+	mov [bpb+bpb_nos], ax
 
 	; update partition offset
 	push si
 	add si, 0x08
-	mov di, po
+	mov di, bpb+bpb_po
 	movsw
 	movsw
 	pop si