Changeset 118 for trunk/bootcode/regular/partmain.asm

Timestamp:

Apr 8, 2017, 12:27:17 AM (8 years ago)

Author:

Ben Rietbroek

Message:

Changed register interface for LBA read/write sector [v1.1.1-testing]

Changed passing the LBA address from BX:CX to BX:AX, so it corresponds
to the load/save sector functions, which do more checking.

This loses the return-status in AH for reading sectors and specifying
write-verify for writing sectors, but that does not really matter.
Status of the last operation should be available using INT13 function
01h and verification of sectors can be done with function 44h if wanted.
CF indicates success or not, which is enough.

This register combination makes it possible to hold both CHS and LBA
sector addresses in registers if needed:
BX:AX ; LBA32
DX:CX ; CHS10

CAUTION:
This is a testbuild !
AirBoot uses the BIOS to access disks and a small coding error can trash
partition tables or other vital disk structures. You are advised to make
backups of TRACK0 and EBRs before using this testbuild. More info at:
​https://rousseaux.github.io/netlabs.air-boot/pdf/AirBoot-v1.1.0-manual.pdf

File:

• trunk/bootcode/regular/partmain.asm (modified) (2 diffs)

trunk/bootcode/regular/partmain.asm

@@ -2263 +2263 @@
         ; Load LBA sector 0 from the disk specified in DL
         xor      bx,bx
-        xor      cx,cx
+        xor      ax,ax
         mov      di,ds
         mov      si,offset [TmpSector]
@@ -2467 +2467 @@
 ;        mov     di,ds
 ;        mov     si,offset [TmpSector]
+;        mov     ax, cx                      ; LBA low is now in AX
 ;        call    DriveIO_ReadSectorLBA