[PATCH v2] platform/x86: dell-wmi-sysman: Clean up security buffer helpers

[Thorsten Blum <thorsten.blum@linux.dev>]

In calculate_security_buffer(), call strlen() once and use ALIGN() to
round up to an even size.

In populate_security_buffer(), also avoid recomputing strlen(), rename
the u32 pointer from 'seclen' to 'seclenp' to avoid confusion with the
new length variable, and drop the memcpy() guard since calling it with
size 0 is a no-op and therefore safe.

Use 'const char *' for the read-only source string in both helpers.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
Changes in v2:
- Include headers (Ilpo)
- Link to v1: https://lore.kernel.org/lkml/20260309211811.82403-3-thorsten.blum@linux.dev/
---
 .../dell/dell-wmi-sysman/dell-wmi-sysman.h    |  4 ++--
 .../x86/dell/dell-wmi-sysman/sysman.c         | 22 +++++++++----------
 2 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/drivers/platform/x86/dell/dell-wmi-sysman/dell-wmi-sysman.h b/drivers/platform/x86/dell/dell-wmi-sysman/dell-wmi-sysman.h
index 817ee7ba07ca..5278a93fdaf7 100644
--- a/drivers/platform/x86/dell/dell-wmi-sysman/dell-wmi-sysman.h
+++ b/drivers/platform/x86/dell/dell-wmi-sysman/dell-wmi-sysman.h
@@ -189,8 +189,8 @@ void exit_bios_attr_set_interface(void);
 int init_bios_attr_set_interface(void);
 int map_wmi_error(int error_code);
 size_t calculate_string_buffer(const char *str);
-size_t calculate_security_buffer(char *authentication);
-void populate_security_buffer(char *buffer, char *authentication);
+size_t calculate_security_buffer(const char *authentication);
+void populate_security_buffer(char *buffer, const char *authentication);
 ssize_t populate_string_buffer(char *buffer, size_t buffer_len, const char *str);
 int set_new_password(const char *password_type, const char *new);
 int init_bios_attr_pass_interface(void);
diff --git a/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c b/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
index 9dddab6c9397..4ae37a1c77f4 100644
--- a/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
+++ b/drivers/platform/x86/dell/dell-wmi-sysman/sysman.c
@@ -7,10 +7,12 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/align.h>
 #include <linux/fs.h>
 #include <linux/dmi.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
+#include <linux/string.h>
 #include <linux/wmi.h>
 #include "dell-wmi-sysman.h"
 #include "../../firmware_attributes_class.h"
@@ -72,13 +74,9 @@ size_t calculate_string_buffer(const char *str)
  *
  * Currently only supported type is Admin password
  */
-size_t calculate_security_buffer(char *authentication)
+size_t calculate_security_buffer(const char *authentication)
 {
-	if (strlen(authentication) > 0) {
-		return (sizeof(u32) * 2) + strlen(authentication) +
-			strlen(authentication) % 2;
-	}
-	return sizeof(u32) * 2;
+	return sizeof(u32) * 2 + ALIGN(strlen(authentication), 2);
 }
 
 /**
@@ -88,18 +86,18 @@ size_t calculate_security_buffer(char *authentication)
  *
  * Currently only supported type is PLAIN TEXT
  */
-void populate_security_buffer(char *buffer, char *authentication)
+void populate_security_buffer(char *buffer, const char *authentication)
 {
+	size_t seclen = strlen(authentication);
 	char *auth = buffer + sizeof(u32) * 2;
 	u32 *sectype = (u32 *) buffer;
-	u32 *seclen = sectype + 1;
+	u32 *seclenp = sectype + 1;
 
-	*sectype = strlen(authentication) > 0 ? 1 : 0;
-	*seclen = strlen(authentication);
+	*sectype = !!seclen;
+	*seclenp = seclen;
 
 	/* plain text */
-	if (strlen(authentication) > 0)
-		memcpy(auth, authentication, *seclen);
+	memcpy(auth, authentication, seclen);
 }
 
 /**