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Date: Fri, 25 Apr 2008 18:12:19 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "Kathy Frazier" <kfrazier@daetwyler-rd.com>
Cc: "'Kathy Frazier'" <kfrazier@daetwyler-rd.com>,
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Subject: Re: Talking to parallel port in 2.6 kernel without using parport
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> One of our engineers downloaded source code a while back from
> linux-2.6.18-rc7, but I am not sure how close that is to what is installed
> on my system (uname -r returns 2.6.18-1.2798.fc6.  When I set my printk to 8
> (echo 8 > /proc/sys/kernel/printk), there are no messages shown on the
> failure.  According to the source code I have, the only silent failure in
> parport_register_device is:

Nothing immediately strikes me.

> When I change the flags from PARPORT_FLAG_EXCL to 0 in the call to
> parport_register_device, the call returns a non-zero to indicate success.

Do you have the printer driver loaded already ? (and does it behave if
you do rmmod lp first)

> Can you tell me what I am missing?  Where can I get the actual source code
> that goes with this version to further unravel this?

>>From the .fc6 it would be an old Fedora kernel so very close to standard
2.6.18 from kernel.org, but the Fedora Core kernels are available from
the Fedora download pages - the .srpm package for each kernel is the one
matching the same binary - so google for "2.6.18-1.2798.fc6.src.rpm"

http://www.mjmwired.net/resources/mjm-fedora-fc6.html has a few notes on
it. 

To be honest this area of the kernel hasn't changed much over recent
times. Let me know if you can't figure out what is going on.