powercap: fix sscanf() error return value handling

[ Upstream commit efc4c35b741af973de90f6826bf35d3b3ac36bf1 ]

Fix inconsistent error handling for sscanf() return value check.

Implicit boolean conversion is used instead of explicit return
value checks. 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@gmail.com>
[ rjw: Subject and changelog edits ]
Link: https://patch.msgid.link/20251207151549.202452-1-sumeet4linux@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/powercap/powercap_sys.c b/drivers/powercap/powercap_sys.c
index 2019b61e7b9014e33fbe0317046316c908733b05..40cf6e337bdef7ab7ed70055a2562fe0fb951b68 100644 (file)
--- a/drivers/powercap/powercap_sys.c
+++ b/drivers/powercap/powercap_sys.c
@@ -67,7 +67,7 @@ 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; \
@@ -92,7 +92,7 @@ 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; \
@@ -161,7 +161,7 @@ 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;