MFSH_UNPHYSTOVIRT - Mark completion of use of virtual address

Purpose   

Release the selector allocated previously by calling MFSH_PHYSTOVIRT. 

Calling Sequence   

int far pascal MFSH_UNPHYSTOVIRT(usSel)

unsigned short usSel;

Where   

usSel contains the selector to released. 
  

Returns   

If no error is detected, a zero error code is returned. If an error is 
detected, the following error code is returned: 

oERROR_PROTECTION_VIOLATION 

the supplied selector is invalid. 
  

Remarks   

This helper is for use by a mini-FSD with an imbedded device driver. It is 
the same as the standard device driver UNPHYSTOVIRT helper. 

A caller must issue a corresponding UNPHYSTOVIRT after calling PHYSTOVIRT, 
before returning to its caller or using any other helpers.