Fix output garbling and allow clean restart after game exit

main.c

@@ -435,6 +435,7 @@ static int kxo_release(struct inode *inode, struct file *filp)
         fast_buf_clear();
     }
     pr_info("release, current cnt: %d\n", atomic_read(&open_cnt));
+    attr_obj.end = 48;
 
     return 0;
 }

xo-user.c

@@ -67,15 +67,15 @@ static void listen_keyboard_handler(void)
             read_attr ^= 1;
             write(attr_fd, buf, 6);
             if (!read_attr)
-                printf("Stopping to display the chess board...\n");
+                printf("\n\nStopping to display the chess board...\n");
             break;
         case 17: /* Ctrl-Q */
             read(attr_fd, buf, 6);
             buf[4] = '1';
             read_attr = false;
             end_attr = true;
             write(attr_fd, buf, 6);
-            printf("Stopping the kernel space tic-tac-toe game...\n");
+            printf("\n\nStopping the kernel space tic-tac-toe game...\n");
             break;
         }
     }
@@ -91,32 +91,45 @@ int main(int argc, char *argv[])
     int flags = fcntl(STDIN_FILENO, F_GETFL, 0);
     fcntl(STDIN_FILENO, F_SETFL, flags | O_NONBLOCK);
 
-    char display_buf[DRAWBUFFER_SIZE];
+    char display_buf[DRAWBUFFER_SIZE];  // Buffer for storing board data read
+                                        // from the device.
 
     fd_set readset;
-    int device_fd = open(XO_DEVICE_FILE, O_RDONLY);
-    int max_fd = device_fd > STDIN_FILENO ? device_fd : STDIN_FILENO;
-    read_attr = true;
-    end_attr = false;
+    int device_fd =
+        open(XO_DEVICE_FILE, O_RDONLY);  // Open the device node to transfer
+                                         // data from kernel to user space.
+    int max_fd = device_fd > STDIN_FILENO
+                     ? device_fd
+                     : STDIN_FILENO;  // The maximum file descriptor required.
+    read_attr = true;                 // true: Continue reading the board
+    end_attr = false;                 // true: Terminate the main loop
 
     while (!end_attr) {
-        FD_ZERO(&readset);
-        FD_SET(STDIN_FILENO, &readset);
-        FD_SET(device_fd, &readset);
-
+        FD_ZERO(&readset);  // Clear readset
+        FD_SET(
+            STDIN_FILENO,
+            &readset);  // Add the file descriptor for standard input to readset
+        FD_SET(device_fd,
+               &readset);  // Add the file descriptor for the device to readset.
+
+        // Wait for any event to occur
         int result = select(max_fd + 1, &readset, NULL, NULL, NULL);
         if (result < 0) {
             printf("Error with select system call\n");
             exit(1);
         }
 
+        // Handle keyboard input events (Ctrl-P or Ctrl-Q)
         if (FD_ISSET(STDIN_FILENO, &readset)) {
             FD_CLR(STDIN_FILENO, &readset);
             listen_keyboard_handler();
+
+            // Display the board
         } else if (read_attr && FD_ISSET(device_fd, &readset)) {
             FD_CLR(device_fd, &readset);
             printf("\033[H\033[J"); /* ASCII escape code to clear the screen */
             read(device_fd, display_buf, DRAWBUFFER_SIZE);
+            display_buf[DRAWBUFFER_SIZE - 1] = '\0';
             printf("%s", display_buf);
         }
     }