linux-kernel - [PATCH 3.16 040/305] driver-core: use 'dev' argument in dev_dbg

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Date:	Sat, 13 Aug 2016 18:42:51 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Dmitry Torokhov" <dmitry.torokhov@...il.com>,
	"Andrew Lunn" <andrew@...n.ch>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	"Arnd Bergmann" <arnd@...db.de>
Subject: [PATCH 3.16 040/305] driver-core: use 'dev' argument in
 dev_dbg_ratelimited stub

3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@...db.de>

commit 1f62ff34a90471d1b735bac2c79e894afc7c59bc upstream.

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")
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 include/linux/device.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1161,8 +1161,11 @@ 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