tried to probe disk geometry with mixed success (emulated FDD mode

on USB not working). Code in stage1 gets too complex to fit 512
bytes, so we most likely must load stage2 with a simple algorithm
(maybe 8 sectors every bios 13h/2h function is able to deliver). Then
we load the kernel in a second, more complex loading step

5 files changed, 43 insertions, 65 deletions

diff --git a/doc/LINKS.TODO b/doc/LINKS.TODO
index 81e0466..c51106b 100644
--- a/doc/LINKS.TODO
+++ b/doc/LINKS.TODO
@@ -70,6 +70,7 @@ https://www.cs.cmu.edu/~410-s07/p4/p4-boot.pdf
 http://www.osdever.net/tutorials/view/loading-sectors
 http://www.osdever.net/tutorials/view/lba-to-chs
 LILO boot loader
+http://www.uruk.org/orig-grub/PC_partitioning.txt
 
 C:
 http://www.drdobbs.com/extending-c-for-object-oriented-programm/184402731
diff --git a/doc/README.DISK_GEOMETRY b/doc/README.DISK_GEOMETRY
index 54f6092..5001679 100644
--- a/doc/README.DISK_GEOMETRY
+++ b/doc/README.DISK_GEOMETRY
@@ -2,69 +2,15 @@ This affects the boot loader in stage 1 using
 BIOS functions to read stage 2 and the kernel
 
 Geometry Specification
-	
 
-360 KB 5.25"
-	
+(emulated) floppy gives us
 
-1.2 MB 5.25"
-	
+0x0101, 0x4f12
 
-720 KB 3.5"
-	
+which is 2 heads, 80 sectors, 18 sectors, sounds good
 
-1.44 MB 3.5"
-	
+Asus, Eeepc 701, pendrive 16 gb:
 
-2.88 MB 3.5"
+0x0000, 0x0012
 
-Tracks (Cylinders)
-	
-
-40
-	
-
-80
-	
-
-80
-	
-
-80
-	
-
-80
-
-Sectors Per Track/Cylinder
-	
-
-9
-	
-
-15
-	
-
-9
-	
-
-18
-	
-
-36
-
-Total Sectors Per Disk
-	
-
-720
-	
-
-2,400
-	
-
-1,440
-	
-
-2,880
-	
-
-5,760
+mmh?
\ No newline at end of file
diff --git a/src/Makefile b/src/Makefile
index 0fbf658..55f8975 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -97,6 +97,10 @@ setjmp.o: setjmp.asm
 clean:
 	-rm -f boot.bin kernel.bin kernel.sym kernel.elf image.bin magic.bin *.o boot.map image.tmp
 
+run-qemu-hd: image.bin
+	qemu-system-i386 -net nic,model=ne2k_pci -d guest_errors -m 32 -drive "file=image.bin,if=ide,format=raw" \
+		-serial file:serial.log
+
 run-qemu: image.bin
 	qemu-system-i386 -net nic,model=ne2k_pci -d guest_errors -m 32 -drive "file=image.bin,if=floppy,format=raw" \
 		-serial file:serial.log
diff --git a/src/boot.asm b/src/boot.asm
index 3f9c127..88f7404 100644
--- a/src/boot.asm
+++ b/src/boot.asm
@@ -40,6 +40,10 @@
 	mov si, MESSAGE_LOADING_STAGE_2
 	call print_string
 
+; detect disk geometry
+	mov dl, [BOOT_DRIVE]
+	call detect_disk_geometry
+
 ; load stage 2 and the kernel together to 0x7e00 (directly
 ; after the boot sector)	
 	mov dl, [BOOT_DRIVE]
diff --git a/src/stage1_functions.asm b/src/stage1_functions.asm
index c17feeb..e9281c4 100644
--- a/src/stage1_functions.asm
+++ b/src/stage1_functions.asm
@@ -91,6 +91,10 @@ current_row:
 	ret
 
 ; data sections used for reading from disk
+SECTORS_PER_CYLINDER:
+	db 0x13				; detect parameters enters the correct value here (sectors + 1)
+NOF_HEADS:
+	db 0x02				; number of heads + 1
 SECTORS_TO_LOAD:
 	db NOF_LOAD_SECTORS		; load NOF_LOAD_SECTORS sectors in total
 CURRENT_SECTOR:
@@ -100,6 +104,23 @@ CURRENT_CYLINDER:
 CURRENT_HEAD:
 	db 0				
 
+; detect disk geometry
+; IN dl: drive
+detect_disk_geometry:
+	mov dx, 0
+	mov es, dx
+	mov ah, 0x08
+	int 0x13
+	add dh, 1
+	mov [NOF_HEADS], BYTE dh
+;	call print_hex
+;	mov dx, cx
+;	call print_hex
+	and cl, 0x3F
+	add cl, 1
+	mov [SECTORS_PER_CYLINDER], BYTE cl
+	ret
+
 ; read the whole stage2 and kernel from the disk
 ; IN dl: drive to read from
 read_from_disk:
@@ -118,14 +139,16 @@ read_from_disk:
 
 	add bx, 0x200			; advance write buffer position
 	add [CURRENT_SECTOR], BYTE 1	; next sector
-	cmp [CURRENT_SECTOR], BYTE 0x13	; assuming 18 sectors per track for now
+	mov ch, [SECTORS_PER_CYLINDER]
+	cmp [CURRENT_SECTOR], ch	; assuming 18 sectors per track for now
 	je .next_head
 	jmp .read_next_sector
 
 .next_head:
 	mov [CURRENT_SECTOR], BYTE 1	; start from first sector again
 	add [CURRENT_HEAD], BYTE 1	; advance head
-	cmp [CURRENT_HEAD], BYTE 0x02	; 2 heads on floppies
+	mov ch, [NOF_HEADS]
+	cmp [CURRENT_HEAD], ch		; 2 heads on floppies
 	je .next_track
 	jmp .read_next_sector
 	
@@ -177,7 +200,7 @@ read_one_sector_from_disk:
 	jmp $
 
 kill_motor:
-	mov	dx, 0x3F2
-	mov	al, 0x00
-	out	dx, al
+	mov dx, 0x3F2
+	mov al, 0x00
+	out dx, al
         ret