Changeset 130 for trunk/bootcode/regular/driveio.asm

Timestamp:

Apr 8, 2017, 12:27:29 AM (8 years ago)

Author:

Ben Rietbroek

Message:

Added a function to calculate pointer to DISKINFO entry [v1.1.1-testing]

The DISKINFO structure will replace all the loose disk related variables
like BIOS_*, LVM_*, LOG_* etc. This function returns a pointer into
the DISKINFO array using the BIOS disk number as the index.

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/driveio.asm (modified) (1 diff)

trunk/bootcode/regular/driveio.asm

@@ -1794 +1794 @@
 DriveIO_GatherDiskInfo  EndP
 
+;------------------------------------------------------------------------------
+; Calculate pointer to entry in DISKINFO structure
+;------------------------------------------------------------------------------
+; IN    : DL BIOS disk number (80h etc)
+; OUT   : BX Pointer to entry
+; NOTE  : BIOS disk number must be valid
+;------------------------------------------------------------------------------
+DriveIO_CalcDiskInfoPointer Proc    Near
+        xchg    bx, ax                          ; AX is used for calculation
+        mov     al, DISKINFO_Size               ; Size of DISKINFO structure
+        mov     ah, dl                          ; BIOS disk number
+        sub     ah, 80h                         ; Now 0-based index
+        mul     ah                              ; Now offset into DISKINFO array
+        add     ax, offset [DiskInformation]    ; Base of DISKINFO array
+        xchg    bx, ax                          ; BX now points to entry for disk
+        ret
+DriveIO_CalcDiskInfoPointer EndP
 
 ;------------------------------------------------------------------------------