From f70242dfa2b1e399096ff9c5c1c554d1014510ee Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Fri, 29 Mar 2019 21:40:44 +0000
Subject: [PATCH] vbr: display drive geometry

---
 boot/vbr.asm | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 74 insertions(+), 2 deletions(-)

diff --git a/boot/vbr.asm b/boot/vbr.asm
index c9628c0..9e10485 100644
--- a/boot/vbr.asm
+++ b/boot/vbr.asm
@@ -58,7 +58,11 @@ _startup:
   mov ss, ax
   xor sp, sp
 
-  mov [fdc.drv], dl ; backup driver number
+  call print_inline
+  db "VBR: Using", 0
+
+  mov [fdc.drv], dl ; backup drive number
+.adjust_chs:
   mov ah, 0x08
   int 0x13 ; required, QEMU detects 360kB as 1200kB with CHS 80 2 15
   jc .noadjust ; skip if function does not exist
@@ -75,11 +79,38 @@ _startup:
   mul word [fdc.nos] ; number of tracks = number of cylinders * heads
   mul word [fdc.spt] ; number of sectors = number of tracks * sectors per track
   mov [fdc.ts], ax
+
+  call print_inline
+  db " BIOS", 0
 .noadjust:
+  call print_inline
+  db " CHS ", 0
+
+  mov ax, [fdc.ts]
+  div word [fdc.nos]
+  div word [fdc.spt]
+  call print_number
+
+  call print_inline
+  db ",", 0
+
+  mov ax, [fdc.nos]
+  call print_number
+
+  call print_inline
+  db ",", 0
+
+  mov ax, [fdc.spt]
+  call print_number
+
+  call print_inline
+  db 0x0A, 0x0D, 0
+
   mov ax, 0x0070
   mov es, ax
   xor bx, bx
   call loadrootdir
+
   call dump
 .end:
   hlt
@@ -149,6 +180,39 @@ loadblk:
   add bx, 0x0200
   ret
 
+print_number:
+  mov cx, 0x000A
+  xor dx, dx
+  div cx ; ax = dx:ax / 10, dx = dx:ax % 10
+  and ax, ax
+  jz .print
+  push dx
+  call print_number
+  pop dx
+.print:
+  mov al, dl
+  add al, 0x30
+  mov ah, 0x0e
+  int 0x10
+  ret
+
+print_inline:
+  pop si
+  push bx
+.loop:
+  lodsb
+  cmp al, 0x00
+  je .end
+  mov bx, 0x0000
+  mov ah, 0x0e
+  int 0x10
+  cmp al, 0x0D
+  jmp .loop
+.end:
+  pop bx
+  push si
+  ret
+
 dump:
   mov si, bx
   mov cx, 0x10
@@ -179,5 +243,13 @@ dump:
 
 %include "print.asm"
 
-times (0x1FE - ($-$$)) nop
+times (0x1F0 - ($-$$)) db 0
+
+str_bootfile:
+  db "BOOT"
+  times (0x1F8 - ($-$$)) db " "
+  db "BIN"
+
+times (0x1FE - ($-$$)) db 0
+
 dw 0xAA55