IRQ conflict with parport and other devices (Re: Wireless issues...)

John dingo at coco2.arach.net.au
Mon Sep 20 00:14:21 UTC 2004


Matt Zimmerman wrote:

>On Sun, Sep 19, 2004 at 12:01:46PM +0100, Matthew Garrett wrote:
>
>  
>
>>On Sun, 2004-09-19 at 09:57 +1000, Chris Edwards wrote:
>>
>>    
>>
>>>I had the same problem with my ipw2100. The solution was to disable the
>>>parallel port in the BIOS. It was trying to use the same IRQ. I suspect
>>>it's an ACPI of APIC issue, and one of the kernel commandline options
>>>might fix it. You're not using a Dell by any chance are you?
>>>      
>>>
>>It seems to be a problem with newer kernels. The parallel port drivers
>>seem to grab IRQ 7 and refuse to let anything else use it. If the
>>parallel port driver is loaded after everything else, it will realise
>>that it can't have the interrupt and use polling instead.
>>    
>>
>
>Yes, creating a problematic situation:
>
>https://bugzilla.ubuntu.com/show_bug.cgi?id=1254
>
>If that is the correct solution, perhaps lp should be loaded by
>init.d/cupsys or similar, rather than init.d/module-init-tools?
>
>Currently, lp is loaded by S20module-init-tools, and then S40hotplug comes
>along and activates other devices which are assigned the same IRQ.
>
>  
>
If the lp module has the IRQ, it is not available to anything else. If 
hotplug is allocating it, hotplug is broken.
Even on my mobo with APIC has it not sharable:
  7:          2    IO-APIC-edge  parport0
As I explained before edge-senstive interrupts are not sharable. The 
reason is they are only detected at the signal transition, and at that 
time interupts for that line can be turned off if there's another device 
attached to it.






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