platform/x86: dell-wmi-sysman: work around for BIOS bug

BIOS sets incorrect value (zero) when SET value passed for integer
attribute with + sign. Added workaround to remove + sign before passing
input to BIOS.

Co-developed-by: Mario Limonciello <mario.limonciello@dell.com>
Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Co-developed-by: Prasanth KSR <prasanth.ksr@dell.com>
Signed-off-by: Prasanth KSR <prasanth.ksr@dell.com>
Signed-off-by: Divya Bharathi <divya.bharathi@dell.com>
Link: https://lore.kernel.org/r/20201202131935.307372-1-divya.bharathi@dell.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/dell-wmi-sysman/int-attributes.c

@@ -39,7 +39,7 @@ static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *a
  * @instance_id: The instance on which input is validated
  * @buf: Input value
  */
-static int validate_integer_input(int instance_id, const char *buf)
+static int validate_integer_input(int instance_id, char *buf)
 {
 	int in_val;
 	int ret;
@@ -51,6 +51,12 @@ static int validate_integer_input(int instance_id, const char *buf)
 			in_val > wmi_priv.integer_data[instance_id].max_value)
 		return -EINVAL;
 
+	/* workaround for BIOS error.
+	 * validate input to avoid setting 0 when integer input passed with + sign
+	 */
+	if (*buf == '+')
+		memmove(buf, (buf + 1), strlen(buf + 1) + 1);
+
 	return ret;
 }