[mnyman-xhci:dbc 5/5] drivers/usb/host/xhci-dbgtty.c:423 xhci_dbc_tty_register_device() warn: unsigned 'port->minor' is never less than zero.

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git dbc
head:   595547d1cfa3f6c591ea084cc1f77cd45bd81213
commit: 595547d1cfa3f6c591ea084cc1f77cd45bd81213 [5/5] xhci: dbgtty: use IDR to support several dbc instances.
config: riscv-randconfig-m031-20220118 (https://download.01.org/0day-ci/archive/20220120/202201200955.C9pzrtCw-lkp@xxxxxxxxx/config)
compiler: riscv32-linux-gcc (GCC) 11.2.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

smatch warnings:
drivers/usb/host/xhci-dbgtty.c:423 xhci_dbc_tty_register_device() warn: unsigned 'port->minor' is never less than zero.

vim +423 drivers/usb/host/xhci-dbgtty.c

   407	
   408	static int xhci_dbc_tty_register_device(struct xhci_dbc *dbc)
   409	{
   410		int			ret;
   411		struct device		*tty_dev;
   412		struct dbc_port		*port = dbc_to_port(dbc);
   413	
   414		if (port->registered)
   415			return -EBUSY;
   416	
   417		xhci_dbc_tty_init_port(dbc, port);
   418	
   419		mutex_lock(&dbc_tty_minors_lock);
   420		port->minor = idr_alloc(&dbc_tty_minors, port, 0, 64, GFP_KERNEL);
   421		mutex_unlock(&dbc_tty_minors_lock);
   422	
 > 423		if (port->minor < 0) {
   424			ret = port->minor;
   425			goto err_idr;
   426		}
   427	
   428		ret = kfifo_alloc(&port->write_fifo, DBC_WRITE_BUF_SIZE, GFP_KERNEL);
   429		if (ret)
   430			goto err_exit_port;
   431	
   432		ret = xhci_dbc_alloc_requests(dbc, BULK_IN, &port->read_pool,
   433					      dbc_read_complete);
   434		if (ret)
   435			goto err_free_fifo;
   436	
   437		ret = xhci_dbc_alloc_requests(dbc, BULK_OUT, &port->write_pool,
   438					      dbc_write_complete);
   439		if (ret)
   440			goto err_free_requests;
   441	
   442		tty_dev = tty_port_register_device(&port->port,
   443						   dbc_tty_driver, port->minor, NULL);
   444		if (IS_ERR(tty_dev)) {
   445			ret = PTR_ERR(tty_dev);
   446			goto err_free_requests;
   447		}
   448	
   449		port->registered = true;
   450	
   451		return 0;
   452	
   453	err_free_requests:
   454		xhci_dbc_free_requests(&port->read_pool);
   455		xhci_dbc_free_requests(&port->write_pool);
   456	err_free_fifo:
   457		kfifo_free(&port->write_fifo);
   458	err_exit_port:
   459		idr_remove(&dbc_tty_minors, port->minor);
   460	err_idr:
   461		xhci_dbc_tty_exit_port(port);
   462	
   463		dev_err(dbc->dev, "can't register tty port, err %d\n", ret);
   464	
   465		return ret;
   466	}
   467	

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