Add drive table initialisation

kernel/drvtab.asm

@@ -0,0 +1,51 @@
+; Drive table
+; Header:
+;	byte	number of drives
+; Item (type BIOS CHS):
+;	byte	type (1)
+;	byte	drive number
+;	word	number of cylinders
+;	byte	number of heads
+;	word	number of sectors per cylinder
+;	3 bytes	padding
+; Item (type BIOS LBA):
+;	byte	type (2)
+;	byte	drive number
+;	dword	offset
+;	dword	size
+
+; Create a drive table at ES:DI
+drvtab_create:
+  mov ax, 0x2B
+  call intr_register
+
+  mov al, 8  ; 8 drives per default
+  mov ah, 10 ; 10 bytes per drive
+  stosb
+  mul ah
+
+  xor cx, cx
+  xchg cx, ax
+  rep stosb
+
+  ret
+
+; Get drive table item
+; IN	DL	drive number (A=0, B=1, ...)
+; OUT	DS:SI	ptr to drive struct
+drvtab_load:
+  push ax
+  mov ax, 0x2B
+  call intr_load
+  cmp dl, [ds:si]
+  jnb .err
+  mov al, 10
+  mul dl
+  inc ax
+  add si, ax
+  pop ax
+  ret
+.err:
+  pop ax
+  stc
+  ret

kernel/main.asm

@@ -65,8 +65,8 @@ putc:
 announce:
   push ds
   push cs
-  mov ax, cs
-  mov ds, ax
+  push cs
+  pop ds
   mov ax, str_product
   push ax
   call printf
@@ -85,15 +85,21 @@ start:
 
   call announce
 
+  call drvtab_create
+
+  int3
+
   cli
 .halt:
   hlt
   jmp .halt
 
+%include "intr.asm"
+%include "drvtab.asm"
+
 %include "printf.inc"
 %include "print.asm"
 
-%include "intr.asm"
 %include "debug.asm"
 
 times 512 nop