move disk enumeration to its own file for the sake of modularity

Makefile

@@ -97,7 +97,7 @@ $(OBJ_DIR)/%.o: $(SRC_DIR)/%.s
 	$(AS) $(ASFLAGS) -o $@ $<
 	$(OBJCOPY) --remove-section .note.gnu.property $@
 
-MBR_TEST_OBJ		=	obj/mbr_test.o obj/serial.o obj/itoa.o obj/util.o
+MBR_TEST_OBJ		=	obj/mbr_test.o obj/serial.o obj/itoa.o obj/util.o obj/test_disk_enum.o
 
 mbr_test: $(MBR_TEST_OBJ) $(DISK)
 	$(LD) -T src/mbr_test.ld -o $(BIN_DIR)/mbr_test.bin $(MBR_TEST_OBJ)

src/mbr_test.s

@@ -36,34 +36,6 @@ entry:
 .bootloader:
     call serial_init
 
-    # enumerate all system disks
+    call test_disk_enum
-    movw $127, disk_id
-    #mov $128, %dl # already set bit 7 to 1 for fixed disk type
-.disk_enum:
-    # set disk id in DL with fixed disk bit on
-    movw disk_id, %dx
-    or $128, %dx
-
-    mov $0x15, %ah
-    int $0x13
-
-    cmp $3, %ah # is fixed disk
-    jnz .disk_skip
-
-    # it's working fixed disk, lets print its number
-    movw disk_id, %ax
-    mov $disk_enum_msg, %si
-    call prints_number
-.disk_skip:
-    decw disk_id
-    jns .disk_enum
-
-    nop
 .halt:
     jmp .halt
-
-.section .rodata
-disk_enum_msg:  .asciz  "Disk "
-
-.section .bss
-disk_id:        .word

src/test_disk_enum.s

@@ -0,0 +1,35 @@
+.section .text
+.code16
+
+.globl test_disk_enum
+
+# enumerate all system disks
+test_disk_enum:
+    movw $127, disk_id
+    #mov $128, %dl # already set bit 7 to 1 for fixed disk type
+.disk_enum:
+    # set disk id in DL with fixed disk bit on
+    movw disk_id, %dx
+    or $128, %dx
+
+    mov $0x15, %ah
+    int $0x13
+
+    cmp $3, %ah # is fixed disk
+    jnz .disk_skip
+
+    # it's working fixed disk, lets print its number
+    movw disk_id, %ax
+    mov $disk_enum_msg, %si
+    call prints_number
+.disk_skip:
+    decw disk_id
+    jns .disk_enum
+
+    ret
+
+.section .rodata
+disk_enum_msg:  .asciz  "Disk "
+
+.section .bss
+disk_id:        .word