linux-kernel - [PATCH] powercap: sscanf return value error handling

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Message-ID: <20251207151549.202452-1-sumeet4linux@gmail.com>
Date: Sun,  7 Dec 2025 20:45:48 +0530
From: Sumeet Pawnikar <sumeet4linux@...il.com>
To: rafael@...nel.org,
	linux-pm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	sumeet4linux@...il.com
Subject: [PATCH] powercap: sscanf return value error handling

Inconsistent error handling for sscanf() return value check.
It uses implicit boolean conversion instead of explicit return
value check. The code checks if (!sscanf(...)) which is incorrect
because:
 1. sscanf returns the number of successfully parsed items
 2. On success, it returns 1 (one item passed)
 3. On failure, it returns 0 or EOF
 4. The check 'if (!sscanf(...))' is wrong because it treats
    success (1) as failure

All occurrences of sscanf() now uses explicit return value check.
With this behavior it returns '-EINVAL' when parsing fails (returns
0 or EOF), and continues when parsing succeeds (returns 1).

Signed-off-by: Sumeet Pawnikar <sumeet4linux@...il.com>
---
 drivers/powercap/powercap_sys.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/powercap/powercap_sys.c b/drivers/powercap/powercap_sys.c
index bdc65e040d17..e998454e4bf6 100644
--- a/drivers/powercap/powercap_sys.c
+++ b/drivers/powercap/powercap_sys.c
@@ -68,7 +68,7 @@ static ssize_t show_constraint_##_attr(struct device *dev, \
 	int id; \
 	struct powercap_zone_constraint *pconst;\
 	\
-	if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id)) \
+	if (sscanf(dev_attr->attr.name, "constraint_%d_", &id) != 1) \
 		return -EINVAL; \
 	if (id >= power_zone->const_id_cnt)	\
 		return -EINVAL; \
@@ -93,7 +93,7 @@ static ssize_t store_constraint_##_attr(struct device *dev,\
 	int id; \
 	struct powercap_zone_constraint *pconst;\
 	\
-	if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id)) \
+	if (sscanf(dev_attr->attr.name, "constraint_%d_", &id) != 1) \
 		return -EINVAL; \
 	if (id >= power_zone->const_id_cnt)	\
 		return -EINVAL; \
@@ -162,7 +162,7 @@ static ssize_t show_constraint_name(struct device *dev,
 	ssize_t len = -ENODATA;
 	struct powercap_zone_constraint *pconst;
 
-	if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id))
+	if (sscanf(dev_attr->attr.name, "constraint_%d_", &id) != 1)
 		return -EINVAL;
 	if (id >= power_zone->const_id_cnt)
 		return -EINVAL;
-- 
2.43.0