==== MFSH_UNPGYSTOVIRT - Mark a completion of use of virtual adress ====

**Purpose**

Release the selector allocated previously by calling //MFSH_PHYSTOVIRT//.   

**Calling Sequence**

<code c>
int far pascal MFSH_UNPHYSTOVIRT(usSel)

unsigned short usSel;
</code>

**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:   

  * ERROR_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.