[PATCH v7 04/12] serial: 8250: expose RX trigger controls for custom callbacks

[James Hilliard <james.hilliard1@gmail.com>]

The rx_trig_bytes attribute dispatches to a port's get_rxtrig and
set_rxtrig callbacks when present, but the attribute group is registered
only when the port type has a static receive-trigger table.

Allow a port that supplies both callbacks to expose the attribute without
a static table. This lets integrations such as Octeon provide their
FIFO-relative thresholds through callbacks while retaining their existing
port type. Require both callbacks because the attribute is read/write;
ports with a static table continue to use the existing fallback handlers.

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
 drivers/tty/serial/8250/8250_port.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 73bc9e7ab703..d87e2b852c3c 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -3152,7 +3152,8 @@ static void register_dev_spec_attr_grp(struct uart_8250_port *up)
 {
 	const struct serial8250_config *conf_type = &uart_config[up->port.type];
 
-	if (conf_type->rxtrig_bytes[0])
+	if (conf_type->rxtrig_bytes[0] ||
+	    (up->port.get_rxtrig && up->port.set_rxtrig))
 		up->port.attr_group = &serial8250_dev_attr_group;
 }
 

-- 
2.53.0