linux-kernel - [PATCH 1/2] scsi: lpfc: avoid harmless comparison warning

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Date:	Wed, 15 Jun 2016 22:42:17 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	"James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	James Smart <james.smart@...gotech.com>,
	Dick Kennedy <dick.kennedy@...gotech.com>,
	Hannes Reinicke <hare@...e.de>,
	James Bottomley <JBottomley@...n.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] scsi: lpfc: avoid harmless comparison warning

When building with -Wextra, we get a lot of warnings for the lpfc driver
concerning expressions that are always true, starting with:

drivers/scsi/lpfc/lpfc_attr.c: In function 'lpfc_enable_npiv_init':
drivers/scsi/lpfc/lpfc_attr.c:2786:77: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]
drivers/scsi/lpfc/lpfc_attr.c: In function 'lpfc_enable_rrq_init':
drivers/scsi/lpfc/lpfc_attr.c:2802:76: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]
drivers/scsi/lpfc/lpfc_attr.c: In function 'lpfc_suppress_link_up_init':
drivers/scsi/lpfc/lpfc_attr.c:2812:2050: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]
drivers/scsi/lpfc/lpfc_attr.c: In function 'lpfc_log_verbose_init':
drivers/scsi/lpfc/lpfc_attr.c:3064:1930: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]

The code works as intented, but it would be nice to shut up the
warning so we don't clutter up build logs with this. Using a
separate inline function for it makes it clear to the compiler
that the comparison is necessary in the caller but still lets
it do the constant-folding.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/scsi/lpfc/lpfc_attr.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_attr.c b/drivers/scsi/lpfc/lpfc_attr.c
index cfec2eca4dd3..3e1d2e669902 100644
--- a/drivers/scsi/lpfc/lpfc_attr.c
+++ b/drivers/scsi/lpfc/lpfc_attr.c
@@ -1620,6 +1620,11 @@ lpfc_sriov_hw_max_virtfn_show(struct device *dev,
 	return snprintf(buf, PAGE_SIZE, "%d\n", max_nr_virtfn);
 }
 
+static inline bool lpfc_rangecheck(uint val, uint min, uint max)
+{
+	return val >= min && val <= max;
+}
+
 /**
  * lpfc_param_show - Return a cfg attribute value in decimal
  *
@@ -1697,7 +1702,7 @@ lpfc_##attr##_show(struct device *dev, struct device_attribute *attr, \
 static int \
 lpfc_##attr##_init(struct lpfc_hba *phba, uint val) \
 { \
-	if (val >= minval && val <= maxval) {\
+	if (lpfc_rangecheck(val, minval, maxval)) {\
 		phba->cfg_##attr = val;\
 		return 0;\
 	}\
@@ -1732,7 +1737,7 @@ lpfc_##attr##_init(struct lpfc_hba *phba, uint val) \
 static int \
 lpfc_##attr##_set(struct lpfc_hba *phba, uint val) \
 { \
-	if (val >= minval && val <= maxval) {\
+	if (lpfc_rangecheck(val, minval, maxval)) {\
 		lpfc_printf_log(phba, KERN_ERR, LOG_INIT, \
 			"3052 lpfc_" #attr " changed from %d to %d\n", \
 			phba->cfg_##attr, val); \
@@ -1856,7 +1861,7 @@ lpfc_##attr##_show(struct device *dev, struct device_attribute *attr, \
 static int \
 lpfc_##attr##_init(struct lpfc_vport *vport, uint val) \
 { \
-	if (val >= minval && val <= maxval) {\
+	if (lpfc_rangecheck(val, minval, maxval)) {\
 		vport->cfg_##attr = val;\
 		return 0;\
 	}\
@@ -1888,7 +1893,7 @@ lpfc_##attr##_init(struct lpfc_vport *vport, uint val) \
 static int \
 lpfc_##attr##_set(struct lpfc_vport *vport, uint val) \
 { \
-	if (val >= minval && val <= maxval) {\
+	if (lpfc_rangecheck(val, minval, maxval)) {\
 		lpfc_printf_vlog(vport, KERN_ERR, LOG_INIT, \
 			"3053 lpfc_" #attr \
 			" changed from %d (x%x) to %d (x%x)\n", \
-- 
2.9.0