Re: [PARPORT] parport driver

Andrea Arcangeli (
Wed, 15 Apr 1998 00:05:45 +0200 (CEST)

On Tue, 14 Apr 1998, Riccardo Facchetti wrote:

>About parport sharing: who is able to explain me the utility of such a
>feature ? I have 1 printer attached to the parport. How about adding
>a parallel ZIP drive ? Can I print WHILE doing backup on the ZIP ?

Sure I do it daily.

>Can I add then another device like a Xircom parallel network interface
>and do network+ZIP backup+printing to the printer with all these devices
>attached to the same parallel interface, all at the same time ?

To share parport there must be a device such as the ZIP drive that is able
to connect/trestate and bypass the line using control commands. A problem
in the parport sharing is the irq handling (you can see my hack of lp for
example to handle that). This because it' s not possible to really share
the interrupt but only to schedule the interrupt between devices. If more
that one device would be interrupt driven the joke became more complex (if
possible). BTW, using lp with ppa at the same time is stable and

>Of course these considerations come from a fresh reading of ECP specs and
>some humbling about actual parport implementation, so it may be totally

I have not read what you have written in detail but please note that the
parallel port don' t run only in ECP.

Ciao ;-).

Andrea[s] Arcangeli

-- To unsubscribe, send mail to: --
-- with the single word "unsubscribe" in the body of the message. --

This archive was generated by hypermail 2.0b3 on Wed 30 Dec 1998 - 10:17:37 EST