> UpCalls

Title: UpCalls
Author: David De Vorchik
History:
        14-May-91 DDV Created.

This document covers the two UpCalls generated by DeviceFS.  These are
generated to inform the outside world that streams have been created or
closed.

UpCall_StreamCreated
--------------------
          
 in:    r0  = UpCall_StreamClosed
        r1  = parent handle
        r2  = 0 for RX, else TX
        r3  = FileSwitch handle being used
        r4  = internal device handle
 
 out:   all should be preserved.

This call is issued when a stream has been created.  It serves as a
broadcast and all registers should be preserved.


UpCall_StreamClosed
-------------------

 in:    r0  = UpCall_StreamClosed
        r1  = parent handle
        r2  = 0 for RX, else TX
        r3  = FileSwitch handle being used
        r4  = internal device handle
 
 out:   -

This call is issued to inform the world that a stream has been closed.

