[Linux-parport] parport_pc disables Hercules mode of mdacon on one pentium

Adam Baker parport at baker-net.org.uk
Fri Jul 23 16:13:44 EDT 2004

On Friday 23 July 2004 01:39, Sindi Keesan wrote:
> I should perhaps have informed those not familiar with these cards that
> Hercules cards INCLUDE a parallel port set to IRQ 7. It takes over as LPT1
> unless you can find some way to disable it (and usually there are no
> jumpers or they are unlabelled).  The onboard parallel port then becomes
> LPT2.  They seem to share an IRQ okay.  I have done plip with this HCG
> parport (but don't know how to do it with LPT2).  On one HGC card plip did
> not work though laplink pro worked.  On another card the parport was dead.

I was going to ask if it was one with a builtin parport and then thought that 
just because I vaguely remembered such a beast from the distant past that 
that probably wasn't the exact card you were referring too. In that case I 
would have a further concern that it doesn't support ECP and EPP modes and 
that the drivers automatic probing for such modes may be writing to registers 
used by the card for other purposes. If that is the case then the patch I 
have got half written to allow specifying the mode as a parameter instead of 
probing might help. I've been writing it for a 2.6 kernel, I don't know if 
parport_pc has changed much since 2.2 so I don't know how difficult it would 
be for you to apply if I ever finish it.
> I will attempt to do this.  Presumably the io address is the same as the
> BIOS default for the onboard LPT1 (378).
> insmod parport_pc io=0x378 irq=7
> (My guess is based on a beginner's experience with ISA ethernet cards).
You can verify that relatively easily yourself - here is an example from my 
$ dmesg | grep -i parport
parport0: PC-style at 0x378 (0x778) [PCSPP,TRISTATE]
parport0: irq 7 detected

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