linux-kernel - [tip:irq/urgent] genirq: generic chip: Use DIV_ROUND

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Date:	Fri, 5 Jul 2013 02:48:57 -0700
From:	tip-bot for Axel Lin <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, grant.likely@...aro.org,
	hpa@...or.com, mingo@...nel.org, tony@...mide.com, arnd@...db.de,
	tglx@...utronix.de, axel.lin@...ics.com
Subject: [tip:irq/urgent] genirq: generic chip:
  Use DIV_ROUND_UP to calculate numchips

Commit-ID:  002fca5df168922103a2bb52748f9984e6de80b2
Gitweb:     http://git.kernel.org/tip/002fca5df168922103a2bb52748f9984e6de80b2
Author:     Axel Lin <axel.lin@...ics.com>
AuthorDate: Fri, 5 Jul 2013 17:13:12 +0800
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 5 Jul 2013 11:39:25 +0200

genirq: generic chip: Use DIV_ROUND_UP to calculate numchips

The number of interrupts in a domain may be not divisible by the
number of interrupts each chip handles. Integer division may truncate
the result, thus use DIV_ROUND_UP to count numchips.

Seems all users of irq_alloc_domain_generic_chips() in current code do
not have this issue. I just found the issue while reading the code.

Signed-off-by: Axel Lin <axel.lin@...ics.com>
Cc: Grant Likely <grant.likely@...aro.org>
Cc: Tony Lindgren <tony@...mide.com>
Cc: Arnd Bergmann <arnd@...db.de>
Link: http://lkml.kernel.org/r/1373015592.18252.2.camel@phoenix
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/irq/generic-chip.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/irq/generic-chip.c b/kernel/irq/generic-chip.c
index 1c39ecc..2f274f3 100644
--- a/kernel/irq/generic-chip.c
+++ b/kernel/irq/generic-chip.c
@@ -278,7 +278,7 @@ int irq_alloc_domain_generic_chips(struct irq_domain *d, int irqs_per_chip,
 	if (d->revmap_type != IRQ_DOMAIN_MAP_LINEAR)
 		return -EINVAL;
 
-	numchips = d->revmap_data.linear.size / irqs_per_chip;
+	numchips = DIV_ROUND_UP(d->revmap_data.linear.size, irqs_per_chip);
 	if (!numchips)
 		return -EINVAL;
 
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