Re: IRQ 15 not assigned, but still unable to use it - in MSDOS it works

[Robert Hancock <hancockrwd@gmail.com>]

On 06/16/2010 05:30 AM, Erik Rull wrote:
> Hi all,
>
> I've worked a lot on bringing the IRQ 15 to work for my embedded system
> but it still fails.
>
> My kernel is the 2.6.29.4 - I've already updated from 2.6.23.3 because
> there were some bugs in some ata drivers.
> My system is a embedded system with Intel ATOM CPU and Intel 965 chipset.
> I need to access some very old ISA-Bus boards. Before I used a Pentium-M
> Board that worked perfect.
> The new board seems to have problems disabling the IRQ 15 in linux. BIOS
> has IRQ 15 reserved for legacy hardware and the IDE port behind it is
> disabled - so IRQ15 should be really free.
> The 2.6.23.3 found an IDE device and said afterwards that it is disabled
> but kept the resources assigned without releasing them - so I was not
> able to use the IRQ15 with my own software.
> With the 2.6.29.4 I don't get this any longer but the IRQ15 doesn't work
> either. Other interrupts are fine (5 or 10) but they are already used by
> other hardware components.
> Now the interesting part: in MSDOS I'm able to see the IRQ15 from the
> ISA board as a source....
>
> So I think that linux somewhere takes the IRQ15 and does not allow me to
> use it - and IRQ sharing seems not to be possible in this case.
>
> I need some ideas where to continue my search - I think that it is
> somewhere in the libata that blocks this interrupt. /proc/interrupts
> shows up no interrupt neither that #15 is used.

If no driver attaches to the device and nothing is reported in 
/proc/interrupts then nothing should be blocking the interrupt 
driver-wise. I suspect the problem might be elsewhere, like the IRQ 
routing or something..