FAS drivers for Xenix 286 2.2.3

[Mark A. Emanuele]

In article <1991Apr21.200251.4273 at ms.uky.edu>, simon at ms.uky.edu (G. Simon Gales) writes:
> I'm trying to replace my sio driver with fas, by porting fas from 386 xenix
> to 286 xenix.  Everything seems almost done, but I'm missing the untimeout()
> (kernel support?) routine.  What is this for?  What does this do?  I don't
> have a device drivers book for 386 xenix so I can't really look it up.
> 	Simon.





     TIMEOUT(K)		       UNIX System V		    TIMEOUT(K)

     Name
	  timeout, untimeout - schedules a time	to execute a routine

     Syntax
	  int
	  timeout(routine, arg,	clock_ticks)
	  int (*routine) ();
	  caddr_t arg;
	  int clock_ticks;

	  void
	  untimeout(id)
	  int id;

     Description
	  timeout schedules a routine to be executed at	a specific
	  time in the future.  timeout returns an integer
	  identification number.  untimeout cancels a timeout request
	  using	the identfication number returned from timeout.

     Note
	  This routine can be used in an interrupt routine only	if the
	  interrupt priority level does	not block the clock interrupt.
	  Do not use if	the level is at	spl6, spl7, splhi, splni or
	  spltty.

     Parameters
	  timeout has the following arguments:

	       routine	      a	routine	to be executed after the
			      specified	number of clock_ticks has
			      elapsed.

	       arg	      passed as	a parameter to routine.

	       clock_ticks    the number of clock ticks	to wait	before
			      calling routine.

	  The argument to untimeout is the integer identification
	  number returned from the timeout call	that you wish to
	  cancel.

     Notes
	  timeout should normally only be used at task time, however
	  it can be used in an xxinit routine with this	caveat.	 Since
	  the clock interrupts may not be enabled before your xxinit
	  routine is called, the timeout may not elapse	when
	  specified, but will elapse no	later than
	  (time_when_clock_started + clock_ticks) times	the length of
	  one clock tick.

     Example
	  timeout(K), sleep(K) and wakeup(K) can be combined to
	  provide  a ``busy, wait'' function.  The following code
	  sample illustrates this possible functionality:

	  #define PERIOD 5	   /* 5	clock ticks */
	  #define BUSYPRI  (PZERO -1)  /* arbitrary */

	  /* Declare routine to	use in timeout(). */
	  int stopwait();

	  /* flag which	is used	to indicate */
	  /* whether to	continue waiting.   */
	  int status;

	  int busywait() /* wait until status is non-zero */
	  {
		  while	(status	== 0) {
			  timeout(stopwait, (caddr_t) &status, PERIOD);
			  sleep(&status, BUSYPRI);
		  }
	  }

	  int stopwait(arg)
	  caddr_t arg;
	  {
		  if ( /* what I am waiting for	has happened */	)
			  status = 1;
		  else
			  wakeup(arg);
	  }

	  A device driver should never loop while waiting for a	status
	  change unless	the delay is less than 100 microseconds. Also,
	  setting a timeout for	fewer than three clock ticks may
	  result in the	sleep call happening after the timeout has
	  occurred. This results in a permanent	sleep condition
	  (hang).

     See Also
	  delay(K), sleep(K), spl(K), wakeup(K)

					              (printed 7/7/89)




Hope this helps

-- 
Mark A. Emanuele
V.P. Engineering  Overleaf, Inc.
218 Summit Ave   Fords, NJ 08863
(908) 738-8486                           emanuele at overlf.UUCP