serdev: Add method to assert break signal over tty UART port

Adds serdev_device_break_ctl() and an implementation for ttyport.
This function simply calls the break_ctl in tty layer, which can
assert a break signal over UART-TX line, if the tty and the
underlying platform and UART peripheral supports this operation.

Signed-off-by: Neeraj Sanjay Kale <neeraj.sanjaykale@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

drivers/tty/serdev/core.c

@@ -405,6 +405,17 @@ int serdev_device_set_tiocm(struct serdev_device *serdev, int set, int clear)
 }
 EXPORT_SYMBOL_GPL(serdev_device_set_tiocm);
 
+int serdev_device_break_ctl(struct serdev_device *serdev, int break_state)
+{
+	struct serdev_controller *ctrl = serdev->ctrl;
+
+	if (!ctrl || !ctrl->ops->break_ctl)
+		return -EOPNOTSUPP;
+
+	return ctrl->ops->break_ctl(ctrl, break_state);
+}
+EXPORT_SYMBOL_GPL(serdev_device_break_ctl);
+
 static int serdev_drv_probe(struct device *dev)
 {
 	const struct serdev_device_driver *sdrv = to_serdev_device_driver(dev->driver);

drivers/tty/serdev/serdev-ttyport.c

@@ -247,6 +247,17 @@ static int ttyport_set_tiocm(struct serdev_controller *ctrl, unsigned int set, u
 	return tty->ops->tiocmset(tty, set, clear);
 }
 
+static int ttyport_break_ctl(struct serdev_controller *ctrl, unsigned int break_state)
+{
+	struct serport *serport = serdev_controller_get_drvdata(ctrl);
+	struct tty_struct *tty = serport->tty;
+
+	if (!tty->ops->break_ctl)
+		return -EOPNOTSUPP;
+
+	return tty->ops->break_ctl(tty, break_state);
+}
+
 static const struct serdev_controller_ops ctrl_ops = {
 	.write_buf = ttyport_write_buf,
 	.write_flush = ttyport_write_flush,
@@ -259,6 +270,7 @@ static const struct serdev_controller_ops ctrl_ops = {
 	.wait_until_sent = ttyport_wait_until_sent,
 	.get_tiocm = ttyport_get_tiocm,
 	.set_tiocm = ttyport_set_tiocm,
+	.break_ctl = ttyport_break_ctl,
 };
 
 struct device *serdev_tty_port_register(struct tty_port *port,

include/linux/serdev.h

@@ -93,6 +93,7 @@ struct serdev_controller_ops {
 	void (*wait_until_sent)(struct serdev_controller *, long);
 	int (*get_tiocm)(struct serdev_controller *);
 	int (*set_tiocm)(struct serdev_controller *, unsigned int, unsigned int);
+	int (*break_ctl)(struct serdev_controller *ctrl, unsigned int break_state);
 };
 
 /**
@@ -203,6 +204,7 @@ int serdev_device_write_buf(struct serdev_device *, const unsigned char *, size_
 void serdev_device_wait_until_sent(struct serdev_device *, long);
 int serdev_device_get_tiocm(struct serdev_device *);
 int serdev_device_set_tiocm(struct serdev_device *, int, int);
+int serdev_device_break_ctl(struct serdev_device *serdev, int break_state);
 void serdev_device_write_wakeup(struct serdev_device *);
 int serdev_device_write(struct serdev_device *, const unsigned char *, size_t, long);
 void serdev_device_write_flush(struct serdev_device *);
@@ -256,6 +258,10 @@ static inline int serdev_device_set_tiocm(struct serdev_device *serdev, int set,
 {
 	return -EOPNOTSUPP;
 }
+static inline int serdev_device_break_ctl(struct serdev_device *serdev, int break_state)
+{
+	return -EOPNOTSUPP;
+}
 static inline int serdev_device_write(struct serdev_device *sdev, const unsigned char *buf,
 				      size_t count, unsigned long timeout)
 {