linux-kernel - Re: [PATCH] irqdomain: print a warning if domains contain IRQ 0

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Date:	Thu, 19 Apr 2012 12:29:17 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Linus Walleij <linus.walleij@...ricsson.com>
Cc:	linux-kernel@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH] irqdomain: print a warning if domains contain IRQ 0

On Thu, 19 Apr 2012 08:23:12 +1000, Benjamin Herrenschmidt <benh@...nel.crashing.org> wrote:
> On Wed, 2012-04-18 at 15:40 +0200, Linus Walleij wrote:
> > From: Linus Walleij <linus.walleij@...aro.org>
> > 
> > Some of the clients using IRQ domains from the ARM VIC
> > (arch/arm/common/vic.c) don't know that their (hardware) IRQ 0
> > is silently ignored by the IRQ core, they will just notice
> > that they're not getting this IRQ anymore. So print a warning
> > if a domain contains IRQ 0 (NO_IRQ) so we get some noise about
> > it atleast.
> 
> I don't understand. HW IRQ 0 is not ignored and works perfectly
> fine on "normal" remapped domains. Or is this specific to "legacy
> domains" ? In this case pls make it clear in the subject :-)

This is indeed specific to the legacy domain.  I think the patch is
good and it will help weed out unintended irq0 users.  However, it
requires the following additional fix I think.  It will need to be
tested to make sure it doesn't break PowerPC ISA users.

g.

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index d0995bd..31f1f88 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -138,7 +138,7 @@ static inline struct irq_domain *irq_domain_add_legacy_isa(
 				const struct irq_domain_ops *ops,
 				void *host_data)
 {
-	return irq_domain_add_legacy(of_node, NUM_ISA_INTERRUPTS, 0, 0, ops,
+	return irq_domain_add_legacy(of_node, NUM_ISA_INTERRUPTS-1, 1, 1, ops,
 				     host_data);
 }
 extern struct irq_domain *irq_find_host(struct device_node *node);


> > ---
> >  kernel/irq/irqdomain.c |    4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> > index 0e0ba5f..1444454 100644
> > --- a/kernel/irq/irqdomain.c
> > +++ b/kernel/irq/irqdomain.c
> > @@ -136,8 +136,10 @@ struct irq_domain *irq_domain_add_legacy(struct device_node *of_node,
> >  		int hwirq = first_hwirq + i;
> >  
> >  		/* IRQ0 gets ignored */
> > -		if (!irq)
> > +		if (!irq) {
> > +			pr_warn("trying to register IRQ 0 (NO_IRQ) in an irq  domain\n");
> >  			continue;
> > +		}
> >  
> >  		/* Legacy flags are left to default at this point,
> >  		 * one can then use irq_create_mapping() to
> 
> 

-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies,Ltd.
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