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Phil Gardner's Wrapper.sys & MS-DOS7 bug (Miscellaneous)

posted by geoffchappell, 12.12.2009, 10:56

> FreeDOS's famous new DEVLOAD (which needs to know whether to create
> FAT32 EDPBs or the normal MS-DOS 4+ DPBs to load block device drivers)
Why would it care about the DOS version for this? To make a DOS drive from the block device's units it needs to make a DPB, yes, but the kernel has a function for this. There's a FAT32 version as int 21h function 7304h subfunction 01h, but in fact, good old int 21h function 53h does the trick as long as you pass 4558h in CX and 4152h in DX. Why can't DEVLOAD try these and just be happy with what it gets if they succeed, whatever the DOS version?

Well, of course, those interfaces are for MS-DOS, but surely FreeDOS has them work the same way. Have I just misunderstood what you mean? There'd be nothing I could do about it anyway.

> Int21.7302/.7304/.7305 is what I recommend to check for, but all of
> these aren't exactly named "FAT32 check" and thus might not be obvious
> at first. They certainly aren't explicit.
If by explicit you want it in letters ten feet high "test for whether DOS has FAT32 support", then no, but that was never very much Microsoft's way in the days of DOS or VxDs. If you want to test that support exists, you try to use the desired support in a way that won't change anything important, but whose success you can assess. That's as explicit as things mostly ever got. There was never a lot of hand-holding.

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