Fintek F81504/508/512 can support both RTS_ON_SEND and RTS_AFTER_SEND, but pci_fintek_rs485_supported only announces the former.

This makes it impossible to unset SER_RS485_RTS_ON_SEND from userspace because of uart_sanitize_serial_rs485(). Some devices with these chips need RTS low on TX, so they are effectively broken.

Fix this by announcing the support for SER_RS485_RTS_AFTER_SEND, similar to commit 068d35a7be65 ("serial: sc16is7xx: announce support for SER_RS485_RTS_ON_SEND").

Fixes: 4afeced55baa ("serial: core: fix sanitizing check for RTS settings") Cc: stable@vger.kernel.org Signed-off-by: Marnix Rijnart marnix.rijnart@iwell.eu ---

Changes in v3: - Rewrite commit message to clarify problem - Use longer commit hashes - v2: https://patch.msgid.link/20260111135933.31316-1-marnix.rijnart@iwell.eu

Changes in v2: - Added fixes tags - Cc stable - v1: https://patch.msgid.link/20250923221756.26770-1-marnix.rijnart@iwell.eu

--- drivers/tty/serial/8250/8250_pci.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c index 152f914c599d..a9da222bd174 100644 --- a/drivers/tty/serial/8250/8250_pci.c +++ b/drivers/tty/serial/8250/8250_pci.c @@ -1645,7 +1645,7 @@ static int pci_fintek_rs485_config(struct uart_port *port, struct ktermios *term }

static const struct serial_rs485 pci_fintek_rs485_supported = { - .flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND, + .flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND, /* F81504/508/512 does not support RTS delay before or after send */ };