[Linux-parport] IRQ 7

Michael Duncan mduncan at mail.psislidell.com
Mon Nov 1 09:37:46 EST 2004


I have a question about irq 7.   I have a special DAQ device attached to 
the parallel port.  At given times this device raises the voltage on pin 
10 (I think) causing an interrupt on IRQ 7.  I have a simple device 
driver that handles this interrupt and services a special device read.

On one box this all works fine, on other boxes it doesn't seen to work 
at all.  The only difference I can see is that on the working machine I 
can grep /var/log/messages and get a line that reads:

Oct 29 13:39:15 fldas kernel: parport0: irq 7 detected

But on the non-working machine I do not get this message.  Both machines 
say the parport is detected at 0x378.  I also have trouble when 
installing an adapter card.  The additional parports (parport1 parport2) 
are detected but only one "irq 7 detected" message for parport0.  

What does the "irq7 detected" mean, and what do I need to do to "detect" 
IRQ 7 when it isn't at boot?  Also, how do I get the adapter card to 
generate interrupts on  IRQ7?    Any help is GREATLY appreciated.


Mike Duncan
Senior Scientist
Planning Systems Inc.

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