hwmon: (dell-smm) Unify i8k_ioctl() and i8k_ioctl_unlocked()

The only purpose of i8k_ioctl() is to call i8k_ioctl_unlocked()
with i8k_mutex held. Judging from the hwmon code, this mutex
only needs to be held when setting the fan speed/mode, so
the operation of I8K_SET_FAN is guaranteed to be atomic.
Unify both functions and reduce the locking of i8k_mutex
to I8K_SET_FAN.

Tested on a Dell Inspiron 3505.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Reviewed-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20211211155422.16830-3-W_Armin@gmx.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/dell-smm-hwmon.c

@@ -449,12 +449,12 @@ static int i8k_get_power_status(void)
  * Procfs interface
  */
 
-static int
-i8k_ioctl_unlocked(struct file *fp, struct dell_smm_data *data, unsigned int cmd, unsigned long arg)
+static long i8k_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
 {
-	int val = 0;
-	int speed, err;
+	struct dell_smm_data *data = PDE_DATA(file_inode(fp));
 	int __user *argp = (int __user *)arg;
+	int speed, err;
+	int val = 0;
 
 	if (!argp)
 		return -EINVAL;
@@ -516,11 +516,13 @@ i8k_ioctl_unlocked(struct file *fp, struct dell_smm_data *data, unsigned int cmd
 		if (copy_from_user(&speed, argp + 1, sizeof(int)))
 			return -EFAULT;
 
+		mutex_lock(&data->i8k_mutex);
 		err = i8k_set_fan(data, val, speed);
 		if (err < 0)
-			return err;
-
+			val = err;
+		else
 			val = i8k_get_fan_status(data, val);
+		mutex_unlock(&data->i8k_mutex);
 		break;
 
 	default:
@@ -536,18 +538,6 @@ i8k_ioctl_unlocked(struct file *fp, struct dell_smm_data *data, unsigned int cmd
 	return 0;
 }
 
-static long i8k_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
-{
-	struct dell_smm_data *data = PDE_DATA(file_inode(fp));
-	long ret;
-
-	mutex_lock(&data->i8k_mutex);
-	ret = i8k_ioctl_unlocked(fp, data, cmd, arg);
-	mutex_unlock(&data->i8k_mutex);
-
-	return ret;
-}
-
 /*
  * Print the information for /proc/i8k.
  */