Patchwork sparc: Provide NO_IRQ definition.

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Submitter David Miller
Date March 18, 2011, 10:04 p.m.
Message ID <20110318.150435.241941372.davem@davemloft.net>
Download mbox | patch
Permalink /patch/87582/
State Accepted
Delegated to: David Miller
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Comments

David Miller - March 18, 2011, 10:04 p.m.
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 arch/sparc/include/asm/irq_32.h |    3 +++
 arch/sparc/include/asm/irq_64.h |    2 ++
 2 files changed, 5 insertions(+), 0 deletions(-)
Sam Ravnborg - March 18, 2011, 10:48 p.m.
On Fri, Mar 18, 2011 at 03:04:35PM -0700, David Miller wrote:
> 
> Signed-off-by: David S. Miller <davem@davemloft.net>
> ---
>  arch/sparc/include/asm/irq_32.h |    3 +++
>  arch/sparc/include/asm/irq_64.h |    2 ++
>  2 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/sparc/include/asm/irq_32.h b/arch/sparc/include/asm/irq_32.h
> index cbf4801..eced3e3 100644
> --- a/arch/sparc/include/asm/irq_32.h
> +++ b/arch/sparc/include/asm/irq_32.h
> @@ -13,4 +13,7 @@
>  #define irq_canonicalize(irq)	(irq)
>  
>  extern void __init init_IRQ(void);
> +
> +#define NO_IRQ		0xffffffff
> +
>  #endif
> diff --git a/arch/sparc/include/asm/irq_64.h b/arch/sparc/include/asm/irq_64.h
> index 4f09666f..16dcae6d 100644
> --- a/arch/sparc/include/asm/irq_64.h
> +++ b/arch/sparc/include/asm/irq_64.h
> @@ -97,4 +97,6 @@ extern void *softirq_stack[NR_CPUS];
>  #define __ARCH_HAS_DO_SOFTIRQ
>  #define ARCH_HAS_NMI_WATCHDOG
>  
> +#define NO_IRQ		0xffffffff
> +
>  #endif

Why -1 (0xffffffff)?

drivers/of/irq.c default to 0 - like this:
/* For archs that don't support NO_IRQ (such as x86), provide a dummy value */
#ifndef NO_IRQ
#define NO_IRQ 0
#endif

I can see that the actual value differs from arch to arch.

I recalled a discussion about this topic some years ago.
Do not ask how I managed to do so?!?

Anyway the input from Linus was to use 0 for NO_IRQ because
as he said:

====
But the point is that most drivers will do something like

	if (!dev->irq)
		return;
(whatever, made up). And that having NO_IRQ be anything but 0 is thus 
fundamentally broken.
====

See the full mail here:

    http://lkml.org/lkml/2005/11/21/211


I do not know of any places that would break - I just
wanted to bring this to your attention.

	Sam
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David Miller - March 18, 2011, 10:50 p.m.
From: Sam Ravnborg <sam@ravnborg.org>
Date: Fri, 18 Mar 2011 23:48:10 +0100

> Why -1 (0xffffffff)?

Because that is what the OF device object creation layer
treats as no-IRQ.

See for example the test in of_device_64.c:build_one_device_irq()
where we go:

	if (irq == 0xffffffff)
		return irq;
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Sam Ravnborg - March 18, 2011, 10:56 p.m.
On Fri, Mar 18, 2011 at 03:50:12PM -0700, David Miller wrote:
> From: Sam Ravnborg <sam@ravnborg.org>
> Date: Fri, 18 Mar 2011 23:48:10 +0100
> 
> > Why -1 (0xffffffff)?
> 
> Because that is what the OF device object creation layer
> treats as no-IRQ.
> 
> See for example the test in of_device_64.c:build_one_device_irq()
> where we go:
> 
> 	if (irq == 0xffffffff)
> 		return irq;

Understood - thanks.

	Sam

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Patch

diff --git a/arch/sparc/include/asm/irq_32.h b/arch/sparc/include/asm/irq_32.h
index cbf4801..eced3e3 100644
--- a/arch/sparc/include/asm/irq_32.h
+++ b/arch/sparc/include/asm/irq_32.h
@@ -13,4 +13,7 @@ 
 #define irq_canonicalize(irq)	(irq)
 
 extern void __init init_IRQ(void);
+
+#define NO_IRQ		0xffffffff
+
 #endif
diff --git a/arch/sparc/include/asm/irq_64.h b/arch/sparc/include/asm/irq_64.h
index 4f09666f..16dcae6d 100644
--- a/arch/sparc/include/asm/irq_64.h
+++ b/arch/sparc/include/asm/irq_64.h
@@ -97,4 +97,6 @@  extern void *softirq_stack[NR_CPUS];
 #define __ARCH_HAS_DO_SOFTIRQ
 #define ARCH_HAS_NMI_WATCHDOG
 
+#define NO_IRQ		0xffffffff
+
 #endif