[RFC PATCH] serial: Don't assume uart_ops .throttle is always set

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

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uart_throttle() assumes that a driver provides a throttle function in
uart_ops. But not all drivers do and there seems to nothing in
serial_core that would set it either. Thus, check it before calling.

Reported-by: Nuno Gonçalves <nunojpg@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

---
 drivers/tty/serial/serial_core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 6a8963caf954..18c9d46e0b85 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -697,7 +697,8 @@ static void uart_throttle(struct tty_struct *tty)
 		mask |= UPSTAT_AUTORTS;
 
 	if (port->status & mask) {
-		port->ops->throttle(port);
+		if (port->ops->throttle)
+			port->ops->throttle(port);
 		mask &= ~port->status;
 	}
 

-- 
tg: (19317433057d..) serial/fix-uart_throttle (depends on: tty-linus)