Subject: Re: Masking out irqs with PCIC_ISA_INTR_ALLOC_MASK in pcmcia subsystem
To: Eric S. Hvozda <hvozda@netcom.com>
From: Jason Thorpe <thorpej@nas.nasa.gov>
List: current-users
Date: 11/10/1997 10:47:24
On Mon, 10 Nov 1997 08:39:30 -0500 
 "Eric S. Hvozda" <hvozda@netcom.com> wrote:

 > I dinally got the D-Link DE-650 working, but it seems that irq 9 
 > is in use on my notebook.
 > 
 > I understand I can mask this irq out with PCIC_ISA_INTR_ALLOC_MASK.
 > 
 > However it's not readily apparent to me how 0xfbff masks irq 10
 > as documented in /sys/dev/isa/i82365_isa.c.  By my calculations
 > it would seem this just masks irq 4; so surely I must be missing the
 > bigger picture...

You don't mask it _out_.  You mask them _in_  :-)  0xffff would allow
IRQs 0 - 15.  If you want to not use IRQ 10, you do:

	0xffff & ~(1 << 10) -> 0xfbff

...so if you also want to exclude IRQ 9:

	0xfbff & ~(1 << 9) -> 0xf9ff

Jason R. Thorpe                                       thorpej@nas.nasa.gov
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