🚀 go-pugleaf

[ rn couldn't deal with all the references, so this is a brand new,
  reference free message.  Sorry, broken software. ]

himacdonald@watdragon.waterloo.edu (Hamish Macdonald) writes:
>Question: Does I/O to Exec devices HAVE to involve message passing?
>Nowhere do
>I see a 'serial.device' task (or anything remotely interpretable as
>such) running.  

new@udel.edu (Darren New) said:
Darren> Well, when I use XOper to look at the ports list, I see a serial.device
Darren> message port generating a software interrupt into a serial.device task.
Darren> It seems to me that if you can do asynchronous calls (like post a read
Darren> and then write or wait for a timeout or ...) then you must be using 
Darren> messages. -- Darren

There's certainly a message port and a soft interrupt, but I don't see a 
task.  I believe serial.device does all its work out of the soft interrupt
on the message port, and a soft interrupt generated by the hardware 
interrupts on the serial port hardware.  Serial.device doesn't do all that 
much, so it doesn't need a task, but you still send messages to it and it 
does not run in your context.

-Dan Riley (riley@tcgould.tn.cornell.edu, cornell!batcomputer!riley)
-Wilson Lab, Cornell University