DosQFSAttach

Query information about an attached file system (local or remote), or about a character device or pseudo-character device attached to the file system.

DosQFSAttach

(DeviceName, Ordinal, FSAInfoLevel, DataBuffer, DataBufferLen, Reserved)

DeviceName (PSZ) - input

Address of a drive letter or the name of a character or pseudo-character device. If DeviceName is a drive, it is an ASCIIZ string having the form of drive letter followed by a colon. If DeviceName is a character or pseudo-character device name, its format is that of an ASCIIZ string in the format of an OS/2 file name in a subdirectory called \DEV\. This parameter is ignored if level 2 or 3 is specified for FSAInfoLevel.
Ordinal (USHORT) - output
Index into the list of character or pseudo-character devices, or the set of drives. Ordinal always starts at 1. The Ordinal position of an item in a list has no significance at all. Ordinal is used strictly to step through the list. The mapping from Ordinal to item is volatile and may change from one call to DosQFSAttach to the next. This parameter is ignored if level 1 is specified for FSAInfoLevel.
FSAInfoLevel (USHORT) - input
Level of information returned in DataBuffer:

o

Level 0001H returns data for the specific drive or device name referred to by DeviceName. The Ordinal field is ignored.
o
Level 0002H returns data for the entry in the list of character or pseudo-character devices selected by Ordinal. The DeviceName field is ignored.
o
Level 0003H returns data for the entry in the list of drives selected by Ordinal. The DeviceName field is ignored.
DataBuffer (PBYTE) - output
Address of the return information buffer, has the following format:

iType (USHORT)

Type of item.

Value

Definition
1
Resident character device
2
Pseudo-character device
3
Local drive
4
Remote drive attached to FSD.
cbName (USHORT)
Length of item name, not counting null.
szName (UCHAR)
Item name, ASCIIZ string.
cbFSDName (USHORT)
Length of FSD name, not counting null.
szFSDName (UCHAR)
Name of FSD item is attached to, ASCIIZ string.
cbFSAData (USHORT)
Length of FSD Attach data returned by FSD.
rgFSAData (UCHAR)
FSD Attach data returned by FSD.
Note:
The szFSDName is the FSD name exported by the FSD, which is not necessarily the same as the FSD name in the boot sector.
For local character devices (iType = 1), cbFSDName = 0 and szFSDName contains only a terminating NULL byte, and cbFSAData = 0.
For local drives (iType = 3), szFSDName contains the name of the FSD attached to the drive at the time of the call. This information changes dynamically. If the drive is attached to the kernel's resident file system, szFSDName contains FAT or unknown. Since the resident file system gets attached to any disk that other FSDs refuse to mount, it is possible to have a disk that does not contain a recognizable file system, but yet gets attached to the resident file system. In this case, it is possible to detect the difference, and this information would help programs in not destroying data on a disk that was not properly recognized.
DataBufferLen (PUSHSHORT) - input/output
Address of the byte length of the return buffer. Upon return, it is the length of the data returned in DataBuffer by the FSD. This field must be initialized.
Reserved (ULONG) - input
Reserved, must be set to zero.
rc (USHORT) - return
Return code descriptions are:
• NO_ERROR 15
  ERROR_INVALID_DRIVE
  111
  ERROR_BUFFER_OVERFLOW
  124
  ERROR_INVALID_LEVEL
  259
  ERROR_NO_MORE_ITEMS
  Remarks

  Information about all block devices and all character and pseudo-character devices is returned by this call.

  The information returned by this call is highly volatile. Calling programs should be aware that the returned information may have already changed by the time it's returned to them.

  The information returned for disks that are attached to the kernel's resident file system can be used to determine if the kernel definitely recognized the disk as one with its file system on it, or if the kernel just attached its file system to it because no other FSDs mounted the disk. This can be important information for a program that needs to know what file system is attached to the drive. It is quite easy to get into a situation where the FSD that recognizes a certain disk has not been installed into the system. In such a case, there is a potential for the data on the disk to be destroyed since the wrong file system is attached to the disk by default.

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