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Subject[PATCH AUTOSEL for 4.14 09/51] serial: 8250_fintek: Fix rs485 disablement on invalid ioctl()
Date
From: Lukas Wunner <lukas@wunner.de>

[ Upstream commit 3236a965486ba0c6043cf2c7b51943d8b382ae29 ]

This driver's ->rs485_config callback checks if SER_RS485_RTS_ON_SEND
and SER_RS485_RTS_AFTER_SEND have the same value. If they do, it means
the user has passed in invalid data with the TIOCSRS485 ioctl()
since RTS must have a different polarity when sending and when not
sending. In this case, rs485 mode is not enabled (the RS485_URA bit
is not set in the RS485 Enable Register) and this is supposed to be
signaled back to the user by clearing the SER_RS485_ENABLED bit in
struct serial_rs485 ... except a missing tilde character is preventing
that from happening.

Fixes: 28e3fb6c4dce ("serial: Add support for Fintek F81216A LPC to 4 UART")
Cc: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Cc: "Ji-Ze Hong (Peter Hong)" <hpeter@gmail.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
---
drivers/tty/serial/8250/8250_fintek.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_fintek.c b/drivers/tty/serial/8250/8250_fintek.c
index e500f7dd2470..9d8f4b78d03b 100644
--- a/drivers/tty/serial/8250/8250_fintek.c
+++ b/drivers/tty/serial/8250/8250_fintek.c
@@ -208,7 +208,7 @@ static int fintek_8250_rs485_config(struct uart_port *port,

if ((!!(rs485->flags & SER_RS485_RTS_ON_SEND)) ==
(!!(rs485->flags & SER_RS485_RTS_AFTER_SEND)))
- rs485->flags &= SER_RS485_ENABLED;
+ rs485->flags &= ~SER_RS485_ENABLED;
else
config |= RS485_URA;

--
2.11.0
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