drivers/tty/serial/serial_core.c:621 uart_write_room() warn: unsigned 'ret' is never less than zero.

[kernel test robot]

tree:   https://github.com/0day-ci/linux/commits/Tony-Lindgren/Get-rid-of-pm_runtime_irq_safe-for-8250_omap/20210922-152808
head:   4456f28c1932b70461a0d8c45d4e863fa9d1be29
commit: 3c7e2a8d4353263d8c5607fc7eca5e4b009f45eb serial: core: Add new prep_tx for power management
date:   6 days ago
config: i386-randconfig-m021-20210927 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0

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

New smatch warnings:
drivers/tty/serial/serial_core.c:621 uart_write_room() warn: unsigned 'ret' is never less than zero.

Old smatch warnings:
drivers/tty/serial/serial_core.c:308 uart_shutdown() error: we previously assumed 'uport' could be null (see line 304)
drivers/tty/serial/serial_core.c:329 uart_shutdown() error: uninitialized symbol 'flags'.
drivers/tty/serial/serial_core.c:2753 iomem_base_show() warn: argument 3 to %lX specifier is cast from pointer

vim +/ret +621 drivers/tty/serial/serial_core.c

   611	
   612	static unsigned int uart_write_room(struct tty_struct *tty)
   613	{
   614		struct uart_state *state = tty->driver_data;
   615		struct uart_port *port;
   616		unsigned long flags;
   617		unsigned int ret;
   618	
   619		port = uart_port_lock(state, flags);
   620		ret = __uart_prep_tx(tty);
 > 621		if (ret < 0) {
   622			uart_port_unlock(port, flags);
   623			return 0;
   624		}
   625	
   626		ret = uart_circ_chars_free(&state->xmit);
   627		uart_port_unlock(port, flags);
   628		return ret;
   629	}
   630	

---
0-DAY CI Kernel Test Service, Intel Corporation
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Attachment: .config.gz
Description: application/gzip