From: Crescent Hsieh <crescentcy.hsieh@moxa.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jirislaby@kernel.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org,
FangpingFP.Cheng@moxa.com, Epson.Chiang@moxa.com,
Crescent Hsieh <crescentcy.hsieh@moxa.com>
Subject: [PATCH v2 12/15] serial: 8250: allow low-level drivers to override break control
Date: Wed, 1 Jul 2026 11:41:25 +0800 [thread overview]
Message-ID: <20260701034128.218569-13-crescentcy.hsieh@moxa.com> (raw)
In-Reply-To: <20260701034128.218569-1-crescentcy.hsieh@moxa.com>
Some UARTs require driver-specific handling for break signaling, which
cannot be expressed by the generic 8250 break implementation alone.
Add an optional uart_port break_ctl callback and route
serial8250_break_ctl() through it when provided. Rename the existing
8250 implementation to serial8250_do_break_ctl() and export it under the
SERIAL_8250_PCI namespace so low-level drivers can reuse the default
8250 behavior when appropriate.
Signed-off-by: Crescent Hsieh <crescentcy.hsieh@moxa.com>
---
drivers/tty/serial/8250/8250_core.c | 2 ++
drivers/tty/serial/8250/8250_port.c | 11 ++++++++++-
include/linux/serial_8250.h | 1 +
include/linux/serial_core.h | 1 +
4 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index bfa421ab3253..0a3355eb4bc3 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -796,6 +796,8 @@ int serial8250_register_8250_port(const struct uart_8250_port *up)
uart->port.startup = up->port.startup;
if (up->port.shutdown)
uart->port.shutdown = up->port.shutdown;
+ if (up->port.break_ctl)
+ uart->port.break_ctl = up->port.break_ctl;
if (up->port.pm)
uart->port.pm = up->port.pm;
if (up->port.handle_break)
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index a17fdb5d68d2..72ecc0112b8a 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1937,7 +1937,7 @@ static void serial8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
serial8250_do_set_mctrl(port, mctrl);
}
-static void serial8250_break_ctl(struct uart_port *port, int break_state)
+void serial8250_do_break_ctl(struct uart_port *port, int break_state)
{
struct uart_8250_port *up = up_to_u8250p(port);
@@ -1950,6 +1950,15 @@ static void serial8250_break_ctl(struct uart_port *port, int break_state)
up->lcr &= ~UART_LCR_SBC;
serial_port_out(port, UART_LCR, up->lcr);
}
+EXPORT_SYMBOL_NS_GPL(serial8250_do_break_ctl, "SERIAL_8250_PCI");
+
+static void serial8250_break_ctl(struct uart_port *port, int break_state)
+{
+ if (port->break_ctl)
+ port->break_ctl(port, break_state);
+ else
+ serial8250_do_break_ctl(port, break_state);
+}
/* Returns true if @bits were set, false on timeout */
static bool wait_for_lsr(struct uart_8250_port *up, int bits)
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index 01efdce0fda0..5ae00dede026 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -192,6 +192,7 @@ void serial8250_do_shutdown(struct uart_port *port);
void serial8250_do_pm(struct uart_port *port, unsigned int state,
unsigned int oldstate);
void serial8250_do_set_mctrl(struct uart_port *port, unsigned int mctrl);
+void serial8250_do_break_ctl(struct uart_port *port, int break_state);
void serial8250_do_set_divisor(struct uart_port *port, unsigned int baud,
unsigned int quot);
int fsl8250_handle_irq(struct uart_port *port);
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 666430b47899..d9e5e3d02003 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -463,6 +463,7 @@ struct uart_port {
void (*shutdown)(struct uart_port *port);
void (*throttle)(struct uart_port *port);
void (*unthrottle)(struct uart_port *port);
+ void (*break_ctl)(struct uart_port *port, int break_state);
int (*handle_irq)(struct uart_port *);
void (*pm)(struct uart_port *, unsigned int state,
unsigned int old);
--
2.45.2
next prev parent reply other threads:[~2026-07-01 3:44 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-01 3:41 [PATCH v2 00/15] serial: 8250: add Moxa MUEx50 PCIe board support Crescent Hsieh
2026-07-01 3:41 ` [PATCH v2 01/15] serial: 8250: split Moxa PCIe serial board support out of 8250_pci Crescent Hsieh
2026-07-01 12:42 ` Andy Shevchenko
2026-07-01 3:41 ` [PATCH v2 02/15] serial: 8250: add Moxa MUEx50 UART port type Crescent Hsieh
2026-07-01 3:41 ` [PATCH v2 03/15] serial: 8250_mxpcie: enable enhanced mode and program FIFO trigger levels Crescent Hsieh
2026-07-01 3:41 ` [PATCH v2 04/15] serial: 8250_mxpcie: enable automatic RTS/CTS flow control Crescent Hsieh
2026-07-01 3:41 ` [PATCH v2 05/15] serial: 8250_mxpcie: offload XON/XOFF flow control to MUEx50 hardware Crescent Hsieh
2026-07-01 3:41 ` [PATCH v2 06/15] serial: 8250_mxpcie: add custom handle_irq callback Crescent Hsieh
2026-07-01 12:41 ` Andy Shevchenko
2026-07-01 3:41 ` [PATCH v2 07/15] serial: 8250_mxpcie: speed up RX using memory-mapped FIFO window Crescent Hsieh
2026-07-01 3:41 ` [PATCH v2 08/15] serial: 8250_mxpcie: speed up TX " Crescent Hsieh
2026-07-01 12:36 ` Andy Shevchenko
2026-07-01 3:41 ` [PATCH v2 09/15] serial: 8250_mxpcie: introduce per-port private data structure Crescent Hsieh
2026-07-01 3:41 ` [PATCH v2 10/15] serial: 8250_mxpcie: defer uart_write_wakeup() to workqueue Crescent Hsieh
2026-07-01 3:41 ` [PATCH v2 11/15] serial: 8250_mxpcie: support serial interface mode switching Crescent Hsieh
2026-07-01 3:41 ` Crescent Hsieh [this message]
2026-07-01 3:41 ` [PATCH v2 13/15] serial: 8250_mxpcie: add break support for RS485 using MUEx50 features Crescent Hsieh
2026-07-01 3:41 ` [PATCH v2 14/15] serial: 8250: allow UART drivers to override rx_trig_bytes handling Crescent Hsieh
2026-07-01 3:41 ` [PATCH v2 15/15] serial: 8250_mxpcie: implement rx_trig_bytes callbacks via MUEx50 RTL Crescent Hsieh
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