hi Jonathan,

 JdBP>   I cannot off hand think of a means whereby you could trigger the
 JdBP> TSR   from *outside* the VDM, though, since VDMs don't have APIs
 JdBP> for most of   the OS/2 IPC primitives, such as semaphores or
 JdBP> queues, and a TSR   wouldn't be much use if it blocked the whole
 JdBP> session on a read of a   named pipe.

Things aren't as bad as you paint them.  From Ralf Brown's Interrupt List,
I get that these OS/2 API calls all are supported in a VDM:

--------O-215702-----------------------------
INT 21 - OS/2 v1.1+ Family API - DosQFileInfo
--------O-215702BXFFFF-----------------------
INT 21 - OS/2 v1.1+ Compatibility Box Family API - DosQPathInfo
--------O-215703-----------------------------
INT 21 - OS/2 v1.1+ Family API - DosSetFileInfo
--------O-215703BXFFFF-----------------------
INT 21 - OS/2 v1.1+ Family API - DosSetPathInfo
--------N-215F32-----------------------------
INT 21 u - Named Pipes - LOCAL DosQNmPipeInfo
--------N-215F33-----------------------------
INT 21 u - Named Pipes - LOCAL DosQNmPHandState
--------N-215F34-----------------------------
INT 21 u - Named Pipes - LOCAL DosSetNmPHandState
--------N-215F35-----------------------------
INT 21 u - Named Pipes - LOCAL DosPeekNmPipe
--------N-215F36-----------------------------
INT 21 u - Named Pipes - LOCAL DosTransactNmPipe
--------N-215F37-----------------------------
INT 21 u - Named Pipes - DosCallNmPipe
--------N-215F38-----------------------------
INT 21 u - Named Pipes - LOCAL DosWaitNmPipe - AWAIT AVAIL. OF PIPE INSTANCE
--------N-215F39-----------------------------
INT 21 U - Named Pipes - LOCAL DosRawReadNmPipe
--------N-215F3A-----------------------------
INT 21 U - Named Pipes - LOCAL DosRawWriteNmPipe
--------O-2164--CX636C-----------------------
INT 21 U - OS/2 v2.1+ Virtual DOS Machine - OS/2 API support
 0025h  DOS32StartSession
 0082h  DosGetCP
 00B6h  DosQFSAttach
 00BFh  DosEditName
 00CBh  DosForceDelete
 0144h  Dos32CreateEventSem
 0145h  Dos32OpenEvenSem
 0146h  Dos32CloseEventSem
 0147h  Dos32ResetEventSem
 0148h  Dos32PostEventSem
 0149h  Dos32WaitEventSem
 014Ah  Dos32QueryEventSem
 014Bh  Dos32CreateMutexSem
 014Ch  Dos32OpenMutexSem
 014Dh  Dos32CloseMutexSem
 014Eh  Dos32RequestMutexSem
 014Fh  Dos32ReleaseMutexSem
 0150h  Dos32QueryMutexSem
 0151h  Dos32CreateMuxWaitSem
 0152h  Dos32OpenMuxWaitSem
 0153h  Dos32CloseMuxWaitSem
 0154h  Dos32WaitMuxWaitSem
 0155h  Dos32AddMuxWaitSem
 0156h  Dos32DeleteMuxWaitSem
 0157h  Dos32QueryMuxWaitSem
--------O-216C01-----------------------------
INT 21 U - OS/2 v2.0 - "DosOpen2"
--------O-216D-------------------------------
INT 21 U - OS/2 v1.x FAPI - "DosMkDir2"
--------O-216E-------------------------------
INT 21 U - OS/2 v1.x FAPI - "DosENumAttrib"
--------O-216F-------------------------------
INT 21 U - OS/2 v1.x FAPI - "DosQMaxEASize" - GET MAXIMUM SIZE OF
EXTENDED ATTR

Should be enough to get that keyboard stuffer going, not?

regards,
         hugo