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Add support for floppy types with other geometry than 18/2/80

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This commit is contained in:
Nero 2020-12-18 18:29:26 +00:00
parent de04b5ca01
commit f10fa026cf
2 changed files with 15 additions and 6 deletions
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16
kernel/drive.asm
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@ -46,6 +46,9 @@ logdrv: ; dont do anything if drive already selected
mov [dsknum], dl
; save info for bios
mov [biosnum], dl
; set default geometry (1.44 MB floppy)
mov word [bpb+BPBNOS], 2
mov word [bpb+BPBSPT], 18
; load boot sector
xor ax, ax
xor dx, dx
@ -61,12 +64,18 @@ logdrv: ; dont do anything if drive already selected
mov [bpb+BPBHS+2], ax
.ret: ret
calchs: mov bx, (18*2)
calchs: ; put sectors per cylinder into bx
mov ax, [bpb+BPBSPT]
mul word [bpb+BPBNOS]
mov bx, ax
; but linear sector num into dx:ax
mov ax, [dskseek]
mov dx, [dskseek+2]
; dx:ax = linear count, bx = sectors / cylinder
div bx
xchg ax, dx
; dx = cylinder, ax = head * spt + sector
mov bl, 18
mov bl, [bpb+BPBSPT]
div byte bl
; dx = cylinder, al = head, ah = sector
xchg dl, dh
@ -134,9 +143,6 @@ dirty: or byte [dskflag], 1 ; dirty
; flush buffer if dirty
flush: test byte [dskflag], 1
jz .ret
; load sector number
mov ax, [dskseek]
mov dx, [dskseek+2]
; do the write
; TODO: error handling & retries
call calchs