Allow arbitrary floppy sizes

Makefile

@@ -1,15 +1,19 @@
+FD_CYLINDERS = 40
+FD_HEADS = 2
+FD_SECTORS = 9
+
 default: kernel.com
 
-boot.bin: kernel/*.asm
+kernel.bin: kernel/*.asm
 	nasm -s -o $@ -I kernel kernel/main.asm
 
-%.bin: boot/%.asm
+boot/%.bin: boot/%.asm
 	nasm -s -o $@ -I lib $<
 
-fdimage.img: fat12vbr.bin boot.bin
-	dd if=/dev/zero bs=512 count=720 of=$@
-	mformat -i $@ -f 360 -B fat12vbr.bin ::
-	mcopy -i fdimage.img boot.bin ::boot.bin
+fdimage.img: boot/floppy.bin kernel.bin
+	dd if=/dev/zero bs=512 count=$$(( $(FD_CYLINDERS) * $(FD_HEADS) * $(FD_SECTORS) )) of=$@
+	mformat -i $@ -t $(FD_CYLINDERS) -h $(FD_HEADS) -n $(FD_SECTORS) -B boot/floppy.bin ::
+	mcopy -i fdimage.img kernel.bin ::boot.bin
 
 clean:
-	rm -f *.com *.bin *.img
+	rm -f *.com *.bin *.img boot/*.bin