From 66f54f639c76f061266a903a831ff9d9faf2cb1e Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Mon, 14 Oct 2019 17:59:48 +0000
Subject: [PATCH] WIP on fcb io

---
 kernel/drive.asm | 36 +++++++++++-------------------------
 kernel/exec.asm  |  6 +-----
 kernel/fcb.asm   | 15 +++++++++------
 kernel/main.asm  |  5 -----
 4 files changed, 21 insertions(+), 41 deletions(-)

diff --git a/kernel/drive.asm b/kernel/drive.asm
index 04599ac..2e1280a 100644
--- a/kernel/drive.asm
+++ b/kernel/drive.asm
@@ -46,8 +46,18 @@ drive_read:
   dec dl
   mov ax, 0x0201
   mov bx, diskbuf
+  ; try read
   int 0x13
-.giveup:
+  jnc .end
+  ; reset disk
+  mov ah, 0x00
+  int 0x13
+  ; loop with si
+  dec si
+  test si, si
+  jnz .try
+  stc
+.end:
   pop si
   pop bx
   pop dx
@@ -57,27 +67,3 @@ drive_read:
 .fast: ; fast lane for boot sector
   inc cl
   jmp .try
-.fail:
-  ; reset disk
-  mov ah, 0x00
-  int 0x13
-  ; loop with si
-  dec si
-  test si, si
-  jnz .try
-  stc
-  jmp .giveup
-
-; Seek to fcb_off given in a ptr
-; IN	BX	ptr to FCB
-drive_seek:
-  push ax
-  push cx
-  mov cl, [bx+fcb_ss]
-  add cl, 7
-  mov ax, 1
-  sal ax, cl
-  int3
-  pop cx
-  pop ax
-  ret
diff --git a/kernel/exec.asm b/kernel/exec.asm
index 6c8f963..9ab3744 100644
--- a/kernel/exec.asm
+++ b/kernel/exec.asm
@@ -7,11 +7,7 @@ exec:
   mov bx, sp
 
   call fcb_parse
-  call fcb_open_blockdev
-  mov cx, 5
-.loop:
-  call fcb_getc
-  loop .loop
+  call fcb_open_rootdir
 
   add sp, 0x20
   pop bx
diff --git a/kernel/fcb.asm b/kernel/fcb.asm
index a5a174c..b945d0a 100644
--- a/kernel/fcb.asm
+++ b/kernel/fcb.asm
@@ -1,3 +1,5 @@
+; diskbuf needs to be defined
+
 ; User-accessible part of FCB (12 bytes)
 %define fcb_drv   0 ; 1 byte, 1=A: 2=B: 3=C:
 %define fcb_fn    1 ; 8 bytes
@@ -19,16 +21,18 @@
 
 %define fcb_end   32
 
-fcb_open_blockdev:
+fcb_open_rootdir:
   mov dl, 0x01
   mov [bx], dl
   dec dl
 
-  ; Init non-user FCB data with zero
+  ; Setup default data
+  ; Default 2 heads, 9 sectors
+  mov word [bx+fcb_spt], 0x0209
   xor ax, ax
-  xor dx, dx
-  lea di, [bx+fcb_spt]
-  mov cx, (fcb_end - fcb_spt)
+  lea di, [bx+fcb_ss]
+  ; Sector & Cluster size 128 bytes
+  mov cx, (fcb_end - fcb_ss)
   rep stosb
 
   ; load first sector
@@ -72,7 +76,6 @@ fcb_get_sector_mask:
 
 fcb_getc:
   push bx
-  call drive_seek
   call fcb_get_sector_mask
   not ax
   and ax, [bx+fcb_off]
diff --git a/kernel/main.asm b/kernel/main.asm
index 76be6db..72efe25 100644
--- a/kernel/main.asm
+++ b/kernel/main.asm
@@ -8,11 +8,6 @@ cpu 8086
 
 %define stack   (diskbuf)
 
-; Metadata for current disk sector
-%define diskptr 0x50
-%define disknum 0x54
-%define diskflg 0x55
-
 %define default_drive BYTE [0x4]
 
 org self