SPC is only allowed when using LFNs provided by a Windows

environment.  So I guess that we have to use the following INT function:

IN

AX = 0x7160 CL = 0x01 CH = SUBST expansion flag, 0x00 = true path for SUBSTed drive letter 0x80 = SUBSTed drive letter DS:SI = ASCIZ FLN ES:DI = buffer for SFN ( max size = 67 or 128 ???  )

OUT

CF = 1 on error AX = error code