IOCTL_MOUNTMGR_NEXT_DRIVE_LETTER IOCTL (mountmgr.h)

Article
05/18/2021

This IOCTL checks to see if the given volume has a drive letter. If it already has a drive letter, or if the volume has a special mount manager database entry indicating that it does not require a drive letter, this routine returns the current drive letter (if there is one) and does nothing. If the given volume does not have a drive letter and does not have a special mount manager database entry indicating that it does not require a drive letter, the next available drive letter is assigned to the volume. If the volume's nonpersistent device name begins with "\Device\Floppy", the mount manager will check for available drive letters starting with the letter "A." If the volume name begins with "\Device\CdRom" the mount manager will check for available drive letters starting with drive letter "D." In all other cases, the mount manager starts with drive letter "C."

Major code

IRP_MJ_DEVICE_CONTROL

Input buffer

The mount manager client initializes the MOUNTMGR_DRIVE_LETTER_TARGET structure, defined in Mountmgr.h, at the beginning of the buffer at Irp->AssociatedIrp.SystemBuffer. The client must insert the name of the target volume at the address pointed to by the DeviceName[] member of this structure. The target volume name is the name of the nonpersistent device object associated with the volume (for example, "\Device\HarddiskVolume1").

Input buffer length

Parameters.DeviceIoControl.InputBufferLength in the I/O stack location of the IRP indicates the size, in bytes, of the input buffer, which must be greater than or equal to sizeof(MOUNTMGR_DRIVE_LETTER_TARGET).

Output buffer

The mount manager inserts either the current drive letter or the newly assigned drive letter (see previous discussion) in the MOUNTMGR_DRIVE_LETTER_INFORMATION structure, defined in Mountmgr.h, at the beginning of the buffer at Irp->AssociatedIrp.SystemBuffer.

Output buffer length

Parameters.DeviceIoControl.OutputBufferLength in the I/O stack location of the IRP indicates the size, in bytes, of the output buffer, which must be greater than or equal to sizeof(MOUNTMGR_DRIVE_LETTER_INFORMATION).

Status block

If the operation is successful , the Status field is set to STATUS_SUCCESS.

If InputBufferLength is less than sizeof(MOUNTMGR_DRIVE_LETTER_TARGET) or if OutputBufferLength is less than sizeof(MOUNTMGR_DRIVE_LETTER_INFORMATION), the Status field is set to STATUS_INVALID_PARAMETER.

Requirements

Requirement	Value
Header	mountmgr.h (include Mountmgr.h)