Commit e8759ad17d41 ("serial: uapi: Add support for bus termination"),
allowed user space to change rs485 bus termination through a flag in
struct serial_rs485. But so far only a single driver, 8250_exar.c,
supports the flag: It hardcodes a GPIO specific to Siemens IOT2040
products.
Provide for a more generic solution: Define a device tree binding
for an rs485 bus termination GPIO (patch [3/4]), amend the serial core
to retrieve the GPIO from the device tree and amend the default
->rs485_config() callback for 8250 drivers to change the GPIO on
request from user space (patch [4/4]).
Retrieving the GPIO from the device tree may fail, so allow
uart_get_rs485_mode() to return an errno and change all callers
to check for failure (patch [2/4]).
Testing has exposed a bug in the 8250 core if retrieval of the GPIO
initially fails with -EPROBE_DEFER and is later retried. That bug
is fixed by patch [1/4].
Lukas Wunner (4):
serial: 8250: Avoid error message on reprobe
serial: Allow uart_get_rs485_mode() to return errno
dt-bindings: serial: Add binding for rs485 bus termination GPIO
serial: 8250: Support rs485 bus termination GPIO
.../devicetree/bindings/serial/rs485.yaml | 4 +++
drivers/tty/serial/8250/8250_core.c | 16 +++++++---
drivers/tty/serial/8250/8250_port.c | 4 +++
drivers/tty/serial/ar933x_uart.c | 6 ++--
drivers/tty/serial/atmel_serial.c | 6 ++--
drivers/tty/serial/fsl_lpuart.c | 5 +++-
drivers/tty/serial/imx.c | 6 +++-
drivers/tty/serial/omap-serial.c | 4 ++-
drivers/tty/serial/serial_core.c | 30 ++++++++++++++++++-
drivers/tty/serial/stm32-usart.c | 8 ++---
include/linux/serial_core.h | 4 ++-
11 files changed, 76 insertions(+), 17 deletions(-)
--
2.26.2
