implement disk parameter reading, tho needs bug fixing

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 obj/test_disk_enum.o
+MBR_TEST_OBJ		=	obj/mbr_test.o obj/serial.o obj/itoa.o obj/util.o obj/test_disk_params.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

@@ -36,6 +36,7 @@ entry:
 .bootloader:
     call serial_init
 
-    call test_disk_enum
+    mov $0x01, %al # disk 1
+    call test_disk_params
 .halt:
     jmp .halt

src/test_disk_params.s

@@ -0,0 +1,63 @@
+.section .text
+.code16
+
+.globl test_disk_params
+
+# al - drive number
+test_disk_params:
+    mov %al, %dl
+    and $128, %dl
+
+    mov $0x08, %al
+    int $0x13
+
+    xor %ax, %ax
+    # write slaves
+    mov %dl, %al
+    movw %ax, disk_slaves
+    # write heads
+    mov %dh, %al
+    movw %ax, disk_heads
+    # write cylinders
+    # write lower part
+    mov %ch, %al
+    # write higher part
+    mov %cl, %ah
+    shr $3, %ah # shift 6 bits to right, because cylinder num's high part is in high 2 bits
+    mov %ax, disk_cylinders
+    # write sectors per cylinder
+    xor %ax, %ax
+    mov %cl, %al
+    and $0b00111111, %al # 6 lower bits are sector count
+    mov %ax, disk_sectors
+
+    # now we can print all this info
+    movw disk_slaves, %ax
+    mov $str_slaves, %si
+    call prints_number
+
+    movw disk_heads, %ax
+    mov $str_heads, %si
+    call prints_number
+
+    movw disk_cylinders, %ax
+    mov $str_cylinders, %si
+    call prints_number
+
+    movw disk_sectors, %ax
+    mov $str_sectors, %si
+    call prints_number
+
+    ret
+
+.section .rodata
+str_slaves:     .asciz "Disk slaves: "
+str_heads:      .asciz "Disk heads: "
+str_cylinders:  .asciz "Disk cylinders: "
+str_sectors:    .asciz "Disk sectors per cylinder: "
+
+.section .bss
+disk_slaves:    .word   # disk attached slaves
+disk_heads:     .word   # number of heads
+disk_cylinders: .word   # number of cylinders
+disk_sectors:   .word   # sectors in cylinder