Lay out skeletons for FCB handling

Makefile

@@ -6,10 +6,11 @@ QEMU = qemu-system-i386
 QEMU_ARGS = $(addprefix --option-rom ,$(ROMS))
 
 VERSION = $(shell git log -1 --format=%cd --date=format:%Y%m%d)
-LABEL = RDOS $(VERSION)
+PRODUCT = rdos
+LABEL = $(PRODUCT) $(VERSION)
 
 NASM = nasm
-NASM_ARGS = -s -Ilib -DVERSION=$(VERSION)
+NASM_ARGS = -s -Ilib -DPRODUCT=$(PRODUCT) -DVERSION=$(VERSION)
 
 KVM = $(shell test -w /dev/kvm && echo 1)
 

boot/fat.asm

@@ -14,6 +14,9 @@ bootsect:	equ 0x7C00 ; our origin before reloc
 
 		%include "inc/bpb.asm"
 
+		%define	V 0x %+ VERSION
+		dd V, V
+
 		times ( 0x0B - ($-$$) ) db 0
 
 params:		times bpb_size db 0

boot/kernel.asm

@@ -22,12 +22,18 @@ print_banner:	mov si, banner
 		cmp al, 0x0D
 		jnz .loop
 
+		call dskrst
+
+		mov dl, 0
+		call dsksel
+
 hlt:		hlt
 		jmp hlt
 
-banner:		db "rdos kernel", 0x0A, 0x0D
+%defstr VERSIONSTR VERSION
+banner:		db "RDOS ", VERSIONSTR, 0x0A, 0x0D
 
-end:		align 512
+%include        "kernel/drive.asm"
 
 section .bss
 

kernel/drive.asm

@@ -1,159 +1,40 @@
 section .bss
 
-drives:		equ 16
+		; drive selected for I/O
-
+dsknum:		resb 1
-		; ptr into currently selected drive
+		; current sector number
-drive_ptr:	resw 1
+dskseek:	resd 1
-
-drive_table:	resb (drives * drive_size)
-
-		; DX and CX for int 13 CHS access
-chs_dx:		resw 1
-chs_cx:		resw 1
 
 		; disk buffer for I/O operations
-diskbuf:	resb 1024
+dskbuf:		resb 512
 
 section .text
 
-drives_init:	; CX = number of floppy drives in the system
+ret:		ret
-		int 0x11
-		mov cl, 6
-		shr ax, cl
-		inc ax
-		and ax, 3
-		mov cx, ax
-
-		mov bx, drive_table
-		xor dx, dx
-
-.loop:		push cx
-		push dx
-		mov [bx+drive.biosnum], dl
-		mov byte [bx+drive.flag], 1 ; 1 = drive letter used
-		; query bios for floppy format
-		mov ah, 8
-		push bx
-		int 0x13
-		pop bx
-		; set up defaults if invalid data or fail
-		jc .defs
-		test cx, cx
-		jnz .load
-.defs:		; use defaults: 360k, 40 cyl, 9 sects
-		les di, [0x1e * 4]
-		mov cx, 0x270
-		mov dh, 1
-.load:		; copy dpt
-		push es
-		push ds
-		pop es
-		pop ds
-		push cx
-		mov si, di
-		lea di, [bx+drive.dpt]
-		mov cx, 11
-		rep movsb
-		pop cx
-		; restore ds
-		push cs
-		pop ds
-		; get and save number of cylinders
-		mov ax, cx
-		xchg al, ah
-		rol ah, 1
-		rol ah, 1
-		and ax, 0x03FF
-		inc ax
-		mov [bx+drive.cylinders], ax
-		; save spt
-		mov ax, cx
-		and al, 0x3F
-		mov [bx+drive.dpt+dpt.lastsector], al
-		; multiply with heads and save sectors per cylinder
-		inc dh
-		mul dh ; ax = al * dh
-		mov [bx+drive.spc], ax
-		; advance loop
-		pop dx
-		pop cx
-		inc dl
-		add bx, drive_size
-		loop .loop
-		ret
 
 		; select drive
 		; IN	dl	drive number
-drive_select:	xor dh, dh
+dsksel:		cmp dl, 1
-		mov ax, drive_size
+		jnc ret
-		mul dx
+		mov al, dl
-		add ax, drive_table
+		and al, 0x02
-		mov word [drive_ptr], ax
-		ret
-
-		; reset currently selected drive
-drive_reset:	mov bx, [drive_ptr]
-		mov dl, [bx+drive.biosnum]
-		; our ptr = CX:BX
-		lea bx, [bx+drive.dpt]
-		mov cx, ds
-		; toggle in our ptr
-		mov si, [0x1E*4]
-		xchg bx, [si]
-		xchg cx, [si+2]
-		; do the call
-		xor ax, ax
-		int 0x13
-		pushf
-		; restore original ptr
-		xchg bx, [si]
-		xchg cx, [si+2]
-		; pass int 13 flags
-		popf
-		ret
-
-		; query status of selected drive
-		; OUT	ah
-drive_status:	mov bx, [drive_ptr]
-		mov dl, [bx+drive.biosnum]
-		mov ah, 1
-		int 0x13
-		ret
-
-		; set sector for read/write operation
-		; IN	dx:ax	32-bit sector number
-drive_seek:	mov bx, [drive_ptr]
-		div word [bx+drive.spc]
-		xchg ax, dx
-		; dx = cylinder, ax = head * spt + sector
-		div byte [bx+drive.dpt+dpt.lastsector]
-		; dx = cylinder, al = head, ah = sector
-		xchg dl, dh
 		ror dl, 1
 		ror dl, 1
-		or dl, ah
+		cmp dl, byte [dsknum]
-		inc dx
+		je ret
-		; al: head number
+
-		; dh bit 0-7: cylinder bits 0-7
+		call dskrst
-		; dl bit 0-5: sector bits 0-5
+
-		; dl bit 6-7: cylinder bits 8-9
+		int 3
-		xchg al, ah
+
-		mov al, [bx+drive.biosnum]
-		; store
-		mov word [chs_dx], ax
-		mov word [chs_cx], dx
 		ret
 
-drive_read:	mov ax, 0x0201
+dskrst:		call flush
-		mov cx, [chs_cx]
+		mov ax, 0xFFFF
-		mov dx, [chs_dx]
+		mov [dsknum], al
-		mov bx, diskbuf
+		mov [dskseek], ax
-		int 0x13
+		mov [dskseek+2], ax
 		ret
 
-drive_write:	mov ax, 0x0301
+		; flush buffer if dirty
-		mov cx, [chs_cx]
+flush:		ret
-		mov dx, [chs_dx]
-		mov bx, diskbuf
-		int 0x13
-		ret

kernel/fcb.asm

@@ -0,0 +1,55 @@
+; in FCB required
+; word	offset in rootdir
+;	used for search
+; word	current cluster
+; byte	record num in cluster
+
+		; FCB open
+fcbopn:		; call fcbfst
+		; copy match
+		; store cluster number in fcb
+		; record = 0
+		ret
+
+		; FCB close
+fcbcls:		; flush disk buffer
+		ret
+
+		; FCB find first
+fcbfst:		; init search state in FCB
+		; jmp to fcbnxt
+		ret
+
+		; FCB find next
+fcbnxt:		; load rootdir sector from state
+		; search until next match
+		; next sec & loop if mismatch
+		; err exit if no further matches
+		ret
+
+		; FCB delete file
+fcbdel:		; call fcbfst
+		; get search state, load root dir from there
+		; mark file as deleted
+		ret
+
+		; FCB read
+		; read sector from cluster into diskbuf
+fcbrd:		; read record from sector
+		; advance record num, carry over to cluster
+		ret
+
+		; FCB write
+fcbwr:		; read sector from cluster into diskbuf
+		; write record into sector
+		; mark buffer dirty
+		; advance record num, carry over to cluster
+		ret
+
+		; FCB create
+fcbcre:
+		ret
+
+		; FCB rename
+fcbren:
+		ret