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Commit 7deb39ed authored by Thomas Pfaff's avatar Thomas Pfaff Committed by Greg Kroah-Hartman
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serial_core: fix uart PORT_UNKNOWN handling 



While porting a RS485 driver from 2.6.29 to 3.14, i noticed that the serial tty
driver could break it by using uart ports that it does not own :

1. uart_change_pm ist called during uart_open and calls the uart pm function
   without checking for PORT_UNKNOWN.
   The fix is to move uart_change_pm from uart_open to uart_port_startup.
2. The return code from the uart request_port call in uart_set_info is not
   handled properly, leading to the situation that the serial driver also
   thinks it owns the uart ports.
   This can triggered by doing following actions :

   setserial /dev/ttyS0 uart none    # release the uart ports
   modprobe lirc-serial              # or any other device that uses the uart
   setserial /dev/ttyS0 uart 16550   # gives no error and the uart tty driver
                                     # can use the ports as well

Signed-off-by: default avatarThomas Pfaff <tpfaff@pcs.com>
Reviewed-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f94b0572

drivers/tty/serial/serial_core.c

+21 −18
Original line number Diff line number Diff line
@@ -136,6 +136,11 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state, 
	if (uport->type == PORT_UNKNOWN)

		return 1;



	/*

	 * Make sure the device is in D0 state.

	 */

	uart_change_pm(state, UART_PM_STATE_ON);



	/*

	 * Initialise and allocate the transmit and temporary

	 * buffer.
@@ -825,13 +830,15 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port, 
		 * If we fail to request resources for the

		 * new port, try to restore the old settings.

		 */

		if (retval && old_type != PORT_UNKNOWN) {

		if (retval) {

			uport->iobase = old_iobase;

			uport->type = old_type;

			uport->hub6 = old_hub6;

			uport->iotype = old_iotype;

			uport->regshift = old_shift;

			uport->mapbase = old_mapbase;



			if (old_type != PORT_UNKNOWN) {

				retval = uport->ops->request_port(uport);

				/*

				 * If we failed to restore the old settings,
@@ -844,6 +851,8 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port, 
				 * We failed anyway.

				 */

				retval = -EBUSY;

			}



			/* Added to return the correct error -Ram Gupta */

			goto exit;

		}
@@ -1570,12 +1579,6 @@ static int uart_open(struct tty_struct *tty, struct file *filp) 
		goto err_dec_count;

	}



	/*

	 * Make sure the device is in D0 state.

	 */

	if (port->count == 1)

		uart_change_pm(state, UART_PM_STATE_ON);



	/*

	 * Start up the serial port.

	 */