修复buzzer驱动bug

buzzer.c

@@ -191,14 +191,15 @@ static ssize_t buzzer_write(struct file *filp, const char __user *buf,
     freq = (dev->buffer[2]<<8) + dev->buffer[1];
     duration = dev->buffer[3];
 
-    if(freq == 0)
-    {
-        mutex_unlock(&dev->lock);
-        return -EINVAL;
-    }
+
 
     if(status_flag == 1)
     {
+        if(freq == 0)
+        {
+            mutex_unlock(&dev->lock);
+            return -EINVAL;
+        }
         BeepOn(freq);
     }
     else