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serial: 8250: allow UART drivers to override rx_trig_bytes handling

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The rx_trig_bytes sysfs attribute currently relies on 8250-internal
helper functions and assumes a fixed mapping between trigger levels and
FIFO behavior.

Some UARTs provide hardware-specific RX trigger mechanisms that do not
fit this model. Add optional uart_port callbacks for setting and getting
the RX trigger level, and use them when provided, while preserving the
existing 8250 helpers as the default fallback.

Signed-off-by: Crescent Hsieh <crescentcy.hsieh@moxa.com>
Link: https://patch.msgid.link/20260731074820.735619-13-crescentcy.hsieh@moxa.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Crescent Hsieh 2026-07-31 15:48:18 +08:00 committed by Greg Kroah-Hartman
parent ade78d3d25
commit 8a6c543cf8
3 changed files with 18 additions and 2 deletions
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4
drivers/tty/serial/8250/8250_core.c
View File

@ -845,6 +845,10 @@ int serial8250_register_8250_port(const struct uart_8250_port *up)
uart->port.get_divisor = up->port.get_divisor;
if (up->port.set_divisor)
uart->port.set_divisor = up->port.set_divisor;
if (up->port.get_rxtrig)
uart->port.get_rxtrig = up->port.get_rxtrig;
if (up->port.set_rxtrig)
uart->port.set_rxtrig = up->port.set_rxtrig;
if (up->port.startup)
uart->port.startup = up->port.startup;
if (up->port.shutdown)

14
drivers/tty/serial/8250/8250_port.c
View File

@ -3035,9 +3035,14 @@ static ssize_t rx_trig_bytes_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct tty_port *port = dev_get_drvdata(dev);
struct uart_state *state = container_of(port, struct uart_state, port);
struct uart_port *uport = state->uart_port;
int rxtrig_bytes;
rxtrig_bytes = do_serial8250_get_rxtrig(port);
if (uport->get_rxtrig)
rxtrig_bytes = uport->get_rxtrig(uport);
else
rxtrig_bytes = do_serial8250_get_rxtrig(port);
if (rxtrig_bytes < 0)
return rxtrig_bytes;
@ -3080,6 +3085,8 @@ static ssize_t rx_trig_bytes_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
struct tty_port *port = dev_get_drvdata(dev);
struct uart_state *state = container_of(port, struct uart_state, port);
struct uart_port *uport = state->uart_port;
unsigned char bytes;
int ret;
@ -3090,7 +3097,10 @@ static ssize_t rx_trig_bytes_store(struct device *dev,
if (ret < 0)
return ret;
ret = do_serial8250_set_rxtrig(port, bytes);
if (uport->set_rxtrig)
ret = uport->set_rxtrig(uport, bytes);
else
ret = do_serial8250_set_rxtrig(port, bytes);
if (ret < 0)
return ret;

2
include/linux/serial_core.h
View File

@ -460,6 +460,8 @@ struct uart_port {
unsigned int baud,
unsigned int quot,
unsigned int quot_frac);
int (*get_rxtrig)(struct uart_port *port);
int (*set_rxtrig)(struct uart_port *port, unsigned char bytes);
int (*startup)(struct uart_port *port);
void (*shutdown)(struct uart_port *port);
void (*throttle)(struct uart_port *port);