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From:   Gioh Kim <gi-oh.kim@ionos.com>
To:     linux-kernel@vger.kernel.org
Cc:     ndesaulniers@google.com, dan.j.williams@intel.com,
        laniel_francis@privacyrequired.com, keescook@chromium.org,
        dja@axtens.net, akpm@linux-foundation.org, haris.iqbal@ionos.com,
        jinpu.wang@ionos.com, Gioh Kim <gi-oh.kim@ionos.com>
Subject: [PATCH v4] lib/string: Introduce sysfs_streqcase
Date:   Thu,  8 Apr 2021 15:06:05 +0200
Message-Id: <20210408130605.541796-1-gi-oh.kim@ionos.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

As the name shows, it checks if strings are equal in case insensitive
manner.

For example, drivers/infiniband/ulp/rtrs/rtrs-clt-sysfs.c uses
strncasecmp to check that the input via sysfs is "mi". But it would
work even-if the input is "min-wrongcommand".

I found some more cases using strncasecmp to check the entire string
such as rtrs-clt-sysfs.c does. drivers/pnp/interface.c checks
"disable" command with strncasecmp but it would also work if the
command is "disable-wrong".

Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com>
---
 include/linux/string.h |  1 +
 lib/string.c           | 36 ++++++++++++++++++++++++++++--------
 2 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/include/linux/string.h b/include/linux/string.h
index 4fcfb56abcf5..36d00ff8013e 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -184,6 +184,7 @@ extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
 extern void argv_free(char **argv);
 
 extern bool sysfs_streq(const char *s1, const char *s2);
+extern bool sysfs_streqcase(const char *s1, const char *s2);
 extern int kstrtobool(const char *s, bool *res);
 static inline int strtobool(const char *s, bool *res)
 {
diff --git a/lib/string.c b/lib/string.c
index 7548eb715ddb..d0fb02efd5da 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -687,6 +687,17 @@ char *strsep(char **s, const char *ct)
 EXPORT_SYMBOL(strsep);
 #endif
 
+static inline bool __streq_terminal(const char *s1, const char *s2)
+{
+	if (*s1 == *s2)
+		return true;
+	if (!*s1 && *s2 == '\n' && !s2[1])
+		return true;
+	if (*s1 == '\n' && !s1[1] && !*s2)
+		return true;
+	return false;
+}
+
 /**
  * sysfs_streq - return true if strings are equal, modulo trailing newline
  * @s1: one string
@@ -703,17 +714,26 @@ bool sysfs_streq(const char *s1, const char *s2)
 		s1++;
 		s2++;
 	}
-
-	if (*s1 == *s2)
-		return true;
-	if (!*s1 && *s2 == '\n' && !s2[1])
-		return true;
-	if (*s1 == '\n' && !s1[1] && !*s2)
-		return true;
-	return false;
+	return __streq_terminal(s1, s2);
 }
 EXPORT_SYMBOL(sysfs_streq);
 
+/**
+ * sysfs_streqcase - same to sysfs_streq and case insensitive
+ * @s1: one string
+ * @s2: another string
+ *
+ */
+bool sysfs_streqcase(const char *s1, const char *s2)
+{
+	while (*s1 && tolower(*s1) == tolower(*s2)) {
+		s1++;
+		s2++;
+	}
+	return __streq_terminal(s1, s2);
+}
+EXPORT_SYMBOL(sysfs_streqcase);
+
 /**
  * match_string - matches given string in an array
  * @array:	array of strings
-- 
2.25.1