Date: Mon, 26 Feb 2001 21:43:51 +0200
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
Sender: halo1 AT zahav DOT net DOT il
To: Martin Str|mberg <ams AT ludd DOT luth DOT se>
Message-Id: <9003-Mon26Feb2001214351+0200-eliz@is.elta.co.il>
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CC: djgpp-workers AT delorie DOT com
In-reply-to: <200102261835.TAA09061@mother.ludd.luth.se> (message from Martin
	Str|mberg on Mon, 26 Feb 2001 19:35:30 +0100 (MET))
Subject: Re: LFN and FreeDOS
References:  <200102261835 DOT TAA09061 AT mother DOT ludd DOT luth DOT se>
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> From: Martin Str|mberg <ams AT ludd DOT luth DOT se>
> Date: Mon, 26 Feb 2001 19:35:30 +0100 (MET)
> 
>   if ((r.x.flags & 1) == 0 && r.x.ax != 0x7100)
>   {
> ...
>   }
>   else
>   {
>     if (r.h.ah == 0x71)
>     {
>       errno = ENOSYS;
>       retval = 0;       /* meaning none of the features supported */
>     }
>     else
>     {
>       /* If the call failed, but not because the OS doesn't support
>          the function (e.g., invalid drive), don't disable LFN.  */
>       errno = __doserr_to_errno(r.x.ax);
>       retval = _FILESYS_UNKNOWN;
>     }
> 
> Why are we accepting carry set and r.x.ax == 1 (1 is the error code
> for "function number invalid")?

Because RBIL says:

INT 21 - Windows95 - LONG FILENAME - GET VOLUME INFORMATION
	AX = 71A0h
	DS:DX -> ASCIZ root name (e.g. "C:\")
	ES:DI -> buffer for file system name
	CX = size of ES:DI buffer
Return: CF clear if successful
	    AX destroyed (0000h and 0200h seen)
	    BX = file system flags (see #01783)
	    CX = maximum length of file name [usually 255]
	    DX = maximum length of path [usually 260]
	    ES:DI buffer filled (ASCIZ, e.g. "FAT","NTFS","CDFS")
	CF set on error
	    AX = error code
		7100h if function not supported

So it looks like either FreeDOS does not comply to what it should be,
or maybe RBIL is inaccurate.

In general, unsupported functions should return something more
prominent than just AX = 1, though.