Hard delays in device drivers

[Mike Massa]

In article <5393 at atexnet.Atex.Kodak.COM> kjl at atex.kodak.com writes:
>O.K. - I'm doing my first device driver for the RS/6000.  I'm trying
>to find out how to insert a time delay for a few microseconds into my
>device initialization routine.  On SunOS (*shudder*) there's a
>"DELAY()" macro which does this.  Does anybody out there know how to
>accomplish the same thing for AIX?
>

The delay() kernel service will suspend a process for some number of timer
ticks (resolution = 0.01 sec). If you need finer resolution, you could
start a timer with tstart(), put the process to sleep with e_sleep(), 
and have the timeout handler function call e_wakeup() to restart your process 
and then exit. You specify the timeout time in nanoseconds with tstart(), 
although I don't know what the resolution is. Quite frankly, the latter is an 
awful lot of work if you can afford to wait a hundreth of a second. If you do 
use tstart() look closely at the timerbuf structure, the argument to the 
timeout handler is a *timerbuf_t, not the argument you specify in the 
timerbuf.

-- 
Mike Massa                            
University of Pennsylvania                         
Distributed Systems Laboratory