tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
1
fork

Configure Feed

Select the types of activity you want to include in your feed.

serial: 8250_pci: Fix broken RS485 for F81504/508/512

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 <stable@kernel.org>
Signed-off-by: Marnix Rijnart <marnix.rijnart@iwell.eu>
Link: https://patch.msgid.link/20260112000931.61703-1-marnix.rijnart@iwell.eu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

authored by

Marnix Rijnart and committed by
Greg Kroah-Hartman 27aff0a5 fb47423d

+1 -1
+1 -1
drivers/tty/serial/8250/8250_pci.c
··· 1658 1658 } 1659 1659 1660 1660 static const struct serial_rs485 pci_fintek_rs485_supported = { 1661 - .flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND, 1661 + .flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND, 1662 1662 /* F81504/508/512 does not support RTS delay before or after send */ 1663 1663 }; 1664 1664