NAME
	DoIO -- perform an I/O command and wait for completion

   SYNOPSIS
	error = DoIO(iORequest)
	D0	     A1

	BYTE DoIO(struct IORequest *);

   FUNCTION
	This function requests a device driver to perform the I/O command
	specified in the I/O request.  This function will always wait until
	the I/O request is fully complete.

	DoIO() handles all the details, including Quick I/O, waiting for
	the request, and removing the reply message, etc..

   IMPLEMENTATION
	This function first tries to complete the IO via the "Quick I/O"
	mechanism.  The io_Flags field is always set to IOF_QUICK (0x01)
	before the internal device call.

	The LN_TYPE field is used internally to flag completion.  Active
	requests have type NT_MESSAGE.  Requests that have been replied
	have type NT_REPLYMSG.  It is illegal to start IO using a
	still active IORequest, or a request with type NT_REPLYMSG.

   INPUTS
	iORequest - pointer to an IORequest initialized by OpenDevice()

   RESULTS
	error - a sign-extended copy of the io_Error field of the
		IORequest.  Most device commands require that the error
		return be checked.

   SEE ALSO
	SendIO(), CheckIO(), WaitIO(), AbortIO(), amiga.lib/BeginIO