This is a note to let you know that I've just added the patch titled
serial: 8250_fintek: Check SER_RS485_RTS_* only with RS485
to the 5.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
serial-8250_fintek-check-ser_rs485_rts_-only-with-rs.patch
and it can be found in the queue-5.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f01914199b5edf2e4eb5d3b2b4192633db1b1b8f
Author: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Date: Fri May 13 16:46:43 2022 +0300
serial: 8250_fintek: Check SER_RS485_RTS_* only with RS485
[ Upstream commit af0179270977508df6986b51242825d7edd59caf ]
SER_RS485_RTS_ON_SEND and SER_RS485_RTS_AFTER_SEND relate to behavior
within RS485 operation. The driver checks if they have the same value
which is not possible to realize with the hardware. The check is taken
regardless of SER_RS485_ENABLED flag and -EINVAL is returned when the
check fails, which creates problems.
This check makes it unnecessarily complicated to turn RS485 mode off as
simple zeroed serial_rs485 struct will trigger that equal values check.
In addition, the driver itself memsets its rs485 structure to zero when
RS485 is disabled but if userspace would try to make an TIOCSRS485
ioctl() call with the very same struct, it would end up failing with
-EINVAL which doesn't make much sense.
Resolve the problem by moving the check inside SER_RS485_ENABLED block.
Fixes: 7ecc77011c6f ("serial: 8250_fintek: Return -EINVAL on invalid configuration")
Cc: Ricardo Ribalda Delgado <ricardo.ribalda@xxxxxxxxx>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/035c738-8ea5-8b17-b1d7-84a7b3aeaa51@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/tty/serial/8250/8250_fintek.c b/drivers/tty/serial/8250/8250_fintek.c
index 251f0018ae8c..dba5950b8d0e 100644
--- a/drivers/tty/serial/8250/8250_fintek.c
+++ b/drivers/tty/serial/8250/8250_fintek.c
@@ -200,12 +200,12 @@ static int fintek_8250_rs485_config(struct uart_port *port,
if (!pdata)
return -EINVAL;
- /* Hardware do not support same RTS level on send and receive */
- if (!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
- !(rs485->flags & SER_RS485_RTS_AFTER_SEND))
- return -EINVAL;
if (rs485->flags & SER_RS485_ENABLED) {
+ /* Hardware do not support same RTS level on send and receive */
+ if (!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
+ !(rs485->flags & SER_RS485_RTS_AFTER_SEND))
+ return -EINVAL;
memset(rs485->padding, 0, sizeof(rs485->padding));
config |= RS485_URA;
} else {
