From 7deb39ed8d9494ea541bcaa69b56036a94f79dc2 Mon Sep 17 00:00:00 2001 From: Thomas Pfaff Date: Wed, 23 Apr 2014 12:33:22 +0200 Subject: [PATCH] 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: Thomas Pfaff Reviewed-by: Alan Cox Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/serial_core.c | 39 +++++++++++++++++--------------- 1 file changed, 21 insertions(+), 18 deletions(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index f26834d262b3..b68550d95a40 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -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. @@ -825,25 +830,29 @@ 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; - retval = uport->ops->request_port(uport); - /* - * If we failed to restore the old settings, - * we fail like this. - */ - if (retval) - uport->type = PORT_UNKNOWN; - /* - * We failed anyway. - */ - retval = -EBUSY; + if (old_type != PORT_UNKNOWN) { + retval = uport->ops->request_port(uport); + /* + * If we failed to restore the old settings, + * we fail like this. + */ + if (retval) + uport->type = PORT_UNKNOWN; + + /* + * 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. */ -- 2.39.5