Re: [PARPORT] Re: IMM driver weirdness.

Matthias Welwarsky (
Fri, 25 Sep 1998 20:54:33 +0200

Philip Blundell wrote:
> >If you use _one_ device per parellel port you won' t use at all the
> >parport scheduling facilities. If you use more than one pardevice on the
> >same parallel port you are agreeing with us.
> I think the problem is that if you try to load PPA or something it wants to
> grab the port so that it can look for devices, even if one isn't in fact
> attached. This will make insmod hang forever if the port is permanently in
> use.

Hi Philip,

you got it right exactly. The mentioned adapter (may it's hardware
design be as flaky as hell ;-) is the only device connected to that very
parport. I didn't make the attempt to share the port with a ZIP drive,
it's just that the ZIP was on a port "behind" the adapter and the imm
driver locked up on probing for the ZIP before ever getting to the port
the ZIP was actually attached to..

So, the strategy I'd suggest for this case is like follows:

1. register the driver to a port
2. try to claim the bus.
3. if claiming the bus fails, check if the device is capable of sharing
the bus
- if not, give up and skip to the next port.
4. spin around p_busy until the bit clears, then immediately reclaim the
bus (atomic action possibly?).


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This archive was generated by hypermail 2.0b3 on Wed 30 Dec 1998 - 10:18:24 EST