==== MFSH_PHYSTOVIRT - Convert physical to virtual adress ====

**Purpose**

Translate the physical address of a data buffer into a virtual address.   

**Calling Sequence**

<code c>
int far pascal MFSH_PHYSTOVIRT(ulAddr, usLen, pusSel)

unsigned long ulAddr;
unsigned short usLen;
unsigned short far * pusSel;
</code>

**Where**

//ulAddr// is the physical address to be translated.   

//usLen// is the length of the segment for the physical address.   

//pusSel// is a pointer to the word in which the selector or segment is returned. 

**Returns**

If an error is not detected, a zero error code is returned. If an error is detected, the following error is returned:   

  * ERROR_PROTECTION_VIOLATION -- the supplied address 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 helper PHYSTOVIRT. A segment/offset pair is returned in real mode for addresses below the 1-Meg boundary. Else a selector/offset pair is returned.   

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