Re: [PATCH] generic irq subsystem: ppc64 port

Re: [PATCH] generic irq subsystem: ppc64 port

[Benjamin Herrenschmidt]

Hi !

That patch will unfortunately break a load of ppc64 boxes.

If you look closely at the ppc64 code, you'll notice we don't
use the irq_desc array directly but go through a get_irq_desc()
accessor. This is because our interrupt numbers can be very
large and scattered, and thus we have a remapping tree.

I still like the idea of the patch, so it would be useful if
you added the possibility for us to just change that behaviour,
that is replace all occursences of irq_descs + i with get_irq_desc()
and provide a generic one that just does that, with a #ifndef so
that the architecture can provide it's own. 

If you agree with the principle, though, I suppose I can do it
and send a proposed patch tomorrow.

Ben.

Re: [PATCH] generic irq subsystem: ppc64 port

[Christoph Hellwig]

On Tue, Oct 19, 2004 at 06:28:20PM +1000, Benjamin Herrenschmidt wrote:
> Hi !
> 
> That patch will unfortunately break a load of ppc64 boxes.
> 
> If you look closely at the ppc64 code, you'll notice we don't
> use the irq_desc array directly but go through a get_irq_desc()
> accessor. This is because our interrupt numbers can be very
> large and scattered, and thus we have a remapping tree.
> 
> I still like the idea of the patch, so it would be useful if
> you added the possibility for us to just change that behaviour,
> that is replace all occursences of irq_descs + i with get_irq_desc()
> and provide a generic one that just does that, with a #ifndef so
> that the architecture can provide it's own. 
> 
> If you agree with the principle, though, I suppose I can do it
> and send a proposed patch tomorrow.

The PPC64 changes were actually my fault.  I think get_irq_desc() is okay.

Re: [PATCH] generic irq subsystem: ppc64 port

[Ingo Molnar]

* Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:

> I still like the idea of the patch, so it would be useful if you added
> the possibility for us to just change that behaviour, that is replace
> all occursences of irq_descs + i with get_irq_desc() and provide a
> generic one that just does that, with a #ifndef so that the
> architecture can provide it's own. 

sure, we could do that. But since there are other architectures with
large irq-vector spaces too, you might want to try to move it into the
generic IRQ code and just provide a way to switch between 1:1 mapped and
sparse-mapped variants.

(of course this still means all of the direct indexing in kernel/irq/*.c
would have to change.)

	Ingo

Re: [PATCH] generic irq subsystem: ppc64 port

[Benjamin Herrenschmidt]

On Tue, 2004-10-19 at 19:15, Ingo Molnar wrote:
> * Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> 
> > I still like the idea of the patch, so it would be useful if you added
> > the possibility for us to just change that behaviour, that is replace
> > all occursences of irq_descs + i with get_irq_desc() and provide a
> > generic one that just does that, with a #ifndef so that the
> > architecture can provide it's own. 
> 
> sure, we could do that. But since there are other architectures with
> large irq-vector spaces too, you might want to try to move it into the
> generic IRQ code and just provide a way to switch between 1:1 mapped and
> sparse-mapped variants.

False alert ! In fact, Paulus rewrote that stuff a while ago and I
totally forgot about it. We no longer do that, our get_irq_desc()
is nowadays just doing (&irq_desc[(irq)]). We map the large
physical interrupt numbers to "virtual" numbers that are the only
thing the generic code sees, so it's fine. 

Ben.