linux-kernel - [PATCH] driver-core: use 'dev' argument in dev_dbg

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Date:	Thu, 24 Mar 2016 22:19:40 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Andrew Lunn <andrew@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Hiroshi Doyu <hdoyu@...dia.com>,
	Aaron Conole <aconole@...hat.com>,
	Arnd Bergmann <arnd@...db.de>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] driver-core: use 'dev' argument in dev_dbg_ratelimited stub

dev_dbg_ratelimited() is a macro that ignores its first argument when DEBUG is
not set, which can lead to unused variable warnings:

ethernet/mellanox/mlxsw/pci.c: In function 'mlxsw_pci_cqe_sdq_handle':
ethernet/mellanox/mlxsw/pci.c:646:18: warning: unused variable 'pdev' [-Wunused-variable]
ethernet/mellanox/mlxsw/pci.c: In function 'mlxsw_pci_cqe_rdq_handle':
ethernet/mellanox/mlxsw/pci.c:671:18: warning: unused variable 'pdev' [-Wunused-variable]

The macro already ensures that all its other arguments are silently
ignored by the compiler without triggering a warning, through the
use of the no_printk() macro, but the dev argument is not passed into
that.

This changes the definition to use the same trick as no_printk() with
an if(0) that leads the compiler to not evaluate the side-effects but
still see that 'dev' might not be unused.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Suggested-by: Andrew Lunn <andrew@...n.ch>
Fixes: 6f586e663e3b ("driver-core: Shut up dev_dbg_reatelimited() without DEBUG")
---
 include/linux/device.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/device.h b/include/linux/device.h
index 002c59728dbe..07f74c246cac 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1293,8 +1293,11 @@ do {									\
 		dev_printk(KERN_DEBUG, dev, fmt, ##__VA_ARGS__);	\
 } while (0)
 #else
-#define dev_dbg_ratelimited(dev, fmt, ...)			\
-	no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
+#define dev_dbg_ratelimited(dev, fmt, ...)				\
+do {									\
+	if (0)								\
+		dev_printk(KERN_DEBUG, dev, fmt, ##__VA_ARGS__);	\
+} while (0)
 #endif
 
 #ifdef VERBOSE_DEBUG
-- 
2.7.0