Changeset 593 in xtideuniversalbios for trunk/Assembly_Library/Src/File/Drive.asm

Timestamp:

Jun 30, 2018, 8:27:04 AM (6 years ago)

Author:

aitotat

Message:

Flashing now works again.
Hack to get Windows 95 to work properly (MODULE_WIN95_CMOS_HACK included for 386 builds by default).
Edited makefile to produce large 386 build.
Fixed recovery time for QDI Vision VLB-IDE controllers.
No more warnings with Nasm 2.13.xx and later.
File dialog now properly restores default drive when file selection is cancelled.

File:

• trunk/Assembly_Library/Src/File/Drive.asm (modified) (2 diffs)

trunk/Assembly_Library/Src/File/Drive.asm

@@ -131 +131 @@
 .IsValidDriveNumberInDL:
     push    ds
+    push    ax
+    cmp     dl, 1
+    jbe     SHORT .FloppyDrive
+
+.MessageSuppressedByInt2FhHandler:
+.MoreThanOneFloppyDrive:
+.NoFloppyDrive:
     push    bx
-    push    ax
 
     inc     dx          ; Default drive is 00h and first drive is 01h
@@ -152 +158 @@
     test    al, al
 
+    pop     bx
+.ReturnFromFloppyDriveFiltering:
     pop     ax
-    pop     bx
     pop     ds
     ret
+
+.FloppyDrive:
+; On single-floppy-drive systems, both A: and B: will point to the same physical drive. The problem is that DOS will print a message telling the user
+; to "insert a disk and press any key to continue" when swapping from one logical drive to the other. To avoid this mess we hook interrupt 2Fh/AX=4A00h
+; to signal to DOS that we will handle this ourselves. However, this only works on DOS 5+ so on older DOS versions we instead try to filter out
+; the "other" logical drive (the one that isn't the current drive) during drive enumeration so the user can't select the "phantom" drive to begin with.
+; This will have the somewhat strange effect of having a drive B: but no drive A: if B: happens to be the current logical floppy drive.
+
+    cmp     BYTE [bDosVersionMajor], 5      ; bDosVersionMajor must be provided by the application as it's not part of the library
+    jae     SHORT .MessageSuppressedByInt2FhHandler
+    LOAD_BDA_SEGMENT_TO ds, ax
+    mov     al, [BDA.wEquipment]
+    test    al, 0C0h
+    jnz     SHORT .MoreThanOneFloppyDrive   ; No phantom drive so no need for any filtering
+    test    al, 1                           ; Any floppy drive at all?
+    jz      SHORT .NoFloppyDrive            ; A pre-DOS 5 machine with no FDD is indeed a strange beast. However, don't trust the BIOS - let DOS decide
+    cmp     dl, [504h]                      ; MS-DOS - LOGICAL DRIVE FOR SINGLE-FLOPPY SYSTEM (A: / B:)
+    jmp     SHORT .ReturnFromFloppyDriveFiltering
 
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