From: "Thomas Pfaff" <tpf...@pcs.com>
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.
2. uart_shutdown is called from uart_set_info and does not check it either.
3. 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 <tpf...@pcs.com>
---
diff -urp linux-3.14.org/drivers/tty/serial/serial_core.c
linux-3.14/drivers/tty/serial/serial_core.c
--- linux-3.14.org/drivers/tty/serial/serial_core.c 2014-03-31
05:40:15.000000000 +0200
+++ linux-3.14/drivers/tty/serial/serial_core.c 2014-04-08 16:51:28.176459065
+0200
@@ -225,6 +225,9 @@ static void uart_shutdown(struct tty_str
struct uart_port *uport = state->uart_port;
struct tty_port *port = &state->port;
+ if (uport->type == PORT_UNKNOWN)
+ return;
+
/*
* Set the TTY IO error marker
*/
@@ -826,25 +829,29 @@ static int uart_set_info(struct tty_stru
* 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;
}
@@ -1900,6 +1907,9 @@ static void uart_change_pm(struct uart_s
{
struct uart_port *port = state->uart_port;
+ if (port->type == PORT_UNKNOWN)
+ return;
+
if (state->pm_state != pm_state) {
if (port->ops->pm)
port->ops->pm(port, pm_state, state->pm_state);
--
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