[tip:irq/core] Document that IRQ_NONE should be returned when IRQ not actually handled

[tip-bot for David Woodhouse]

Commit-ID:  d9e4ad5badf4ccbfddee208c898fb8fd0c8836b1
Gitweb:     http://git.kernel.org/tip/d9e4ad5badf4ccbfddee208c898fb8fd0c8836b1
Author:     David Woodhouse <dwmw2@xxxxxxxxxxxxx>
AuthorDate: Wed, 28 Oct 2015 16:14:31 +0900
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Fri, 30 Oct 2015 10:13:26 +0100

Document that IRQ_NONE should be returned when IRQ not actually handled

Our IRQ storm detection works when an interrupt handler returns
IRQ_NONE for thousands of consecutive interrupts in a second. It
doesn't hurt to occasionally return IRQ_NONE when the interrupt is
actually genuine.

Drivers should only be returning IRQ_HANDLED if they have actually
*done* something to stop an interrupt from happening â it doesn't just
mean "this really *was* my device".

Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
Cc: davem@xxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1446016471.3405.201.camel@xxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 include/linux/irqreturn.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/irqreturn.h b/include/linux/irqreturn.h
index e374e36..eb1bdcf 100644
--- a/include/linux/irqreturn.h
+++ b/include/linux/irqreturn.h
@@ -3,7 +3,7 @@
 
 /**
  * enum irqreturn
- * @IRQ_NONE		interrupt was not from this device
+ * @IRQ_NONE		interrupt was not from this device or was not handled
  * @IRQ_HANDLED		interrupt was handled by this device
  * @IRQ_WAKE_THREAD	handler requests to wake the handler thread
  */
--
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