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serial: core: fix sanitizing check for RTS settings 

Among other things uart_sanitize_serial_rs485() tests the sanity of the RTS
settings in a RS485 configuration that has been passed by userspace.
If RTS-on-send and RTS-after-send are both set or unset the configuration
is adjusted and RTS-after-send is disabled and RTS-on-send enabled.

This however makes only sense if both RTS modes are actually supported by
the driver.

With commit be2e2cb1d2 ("serial: Sanitize rs485_struct") the code does
take the driver support into account but only checks if one of both RTS
modes are supported. This may lead to the errorneous result of RTS-on-send
being set even if only RTS-after-send is supported.

Fix this by changing the implemented logic: First clear all unsupported
flags in the RS485 configuration, then adjust an invalid RTS setting by
taking into account which RTS mode is supported.

Cc:  <stable@vger.kernel.org>
Fixes: be2e2cb1d2 ("serial: Sanitize rs485_struct")
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
Link: https://lore.kernel.org/r/20240103061818.564-4-l.sanfilippo@kunbus.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Lino Sanfilippo 2024-01-03 07:18:14 +01:00 committed by Greg Kroah-Hartman
parent 1a33e33ca0
commit 4afeced55b
1 changed files with 20 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
drivers/tty/serial/serial_core.c
View File

@ -1376,20 +1376,28 @@ static void uart_sanitize_serial_rs485(struct uart_port *port, struct serial_rs4
return;
}
/* Pick sane settings if the user hasn't */
if ((supported_flags & (SER_RS485_RTS_ON_SEND|SER_RS485_RTS_AFTER_SEND)) &&
!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
!(rs485->flags & SER_RS485_RTS_AFTER_SEND)) {
dev_warn_ratelimited(port->dev,
"%s (%d): invalid RTS setting, using RTS_ON_SEND instead\n",
port->name, port->line);
rs485->flags |= SER_RS485_RTS_ON_SEND;
rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
supported_flags |= SER_RS485_RTS_ON_SEND|SER_RS485_RTS_AFTER_SEND;
}
rs485->flags &= supported_flags;
/* Pick sane settings if the user hasn't */
if (!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
!(rs485->flags & SER_RS485_RTS_AFTER_SEND)) {
if (supported_flags & SER_RS485_RTS_ON_SEND) {
rs485->flags |= SER_RS485_RTS_ON_SEND;
rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
dev_warn_ratelimited(port->dev,
"%s (%d): invalid RTS setting, using RTS_ON_SEND instead\n",
port->name, port->line);
} else {
rs485->flags |= SER_RS485_RTS_AFTER_SEND;
rs485->flags &= ~SER_RS485_RTS_ON_SEND;
dev_warn_ratelimited(port->dev,
"%s (%d): invalid RTS setting, using RTS_AFTER_SEND instead\n",
port->name, port->line);
}
}
uart_sanitize_serial_rs485_delays(port, rs485);
/* Return clean padding area to userspace */