[PATCH 1/4] TTY: use class_find_device to find port in uart_suspend/resume.

[NeilBrown <neil@brown.name>]

uart_{suspend,resume}_port search the children of a uart device
to find a particular tty device.
This requires all the ttys to be direct children of the uart.

A future patch will allow a 'tty_slave' to intervene between
the port and the uart, voiding this requirement.

So change to use class_find_device.  This is made possible by
exporting a "tty_find_device" from tty_io.c.

This new "tty_find_device" is very similar to the existing
tty_get_device() which has a single caller, so discard
tty_get_device() and just use tty_find_device().

Signed-off-by: NeilBrown <neil@brown.name>
---
 drivers/tty/serial/serial_core.c |   21 ++++++++-------------
 drivers/tty/tty_io.c             |    6 +++---
 include/linux/tty.h              |    1 +
 3 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index eb5b03be9dfd..3ea16f524e89 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2005,26 +2005,19 @@ struct uart_match {
 	struct uart_driver *driver;
 };
 
-static int serial_match_port(struct device *dev, void *data)
-{
-	struct uart_match *match = data;
-	struct tty_driver *tty_drv = match->driver->tty_driver;
-	dev_t devt = MKDEV(tty_drv->major, tty_drv->minor_start) +
-		match->port->line;
-
-	return dev->devt == devt; /* Actually, only one tty per port */
-}
 
 int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
 {
 	struct uart_state *state = drv->state + uport->line;
 	struct tty_port *port = &state->port;
 	struct device *tty_dev;
-	struct uart_match match = {uport, drv};
+	dev_t devt = MKDEV(drv->tty_driver->major,
+			   drv->tty_driver->minor_start) +
+		uport->line;
 
 	mutex_lock(&port->mutex);
 
-	tty_dev = device_find_child(uport->dev, &match, serial_match_port);
+	tty_dev = tty_find_device(devt);
 	if (device_may_wakeup(tty_dev)) {
 		if (!enable_irq_wake(uport->irq))
 			uport->irq_wake = 1;
@@ -2084,12 +2077,14 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
 	struct uart_state *state = drv->state + uport->line;
 	struct tty_port *port = &state->port;
 	struct device *tty_dev;
-	struct uart_match match = {uport, drv};
 	struct ktermios termios;
+	dev_t devt = MKDEV(drv->tty_driver->major,
+			   drv->tty_driver->minor_start) +
+		uport->line;
 
 	mutex_lock(&port->mutex);
 
-	tty_dev = device_find_child(uport->dev, &match, serial_match_port);
+	tty_dev = tty_find_device(devt);
 	if (!uport->suspended && device_may_wakeup(tty_dev)) {
 		if (uport->irq_wake) {
 			disable_irq_wake(uport->irq);
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index e5695467598f..ccb99b772965 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3077,11 +3077,11 @@ static int dev_match_devt(struct device *dev, const void *data)
 }
 
 /* Must put_device() after it's unused! */
-static struct device *tty_get_device(struct tty_struct *tty)
+struct device *tty_find_device(dev_t devt)
 {
-	dev_t devt = tty_devnum(tty);
 	return class_find_device(tty_class, NULL, &devt, dev_match_devt);
 }
+EXPORT_SYMBOL(tty_find_device);
 
 
 /**
@@ -3123,7 +3123,7 @@ struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
 	tty->ops = driver->ops;
 	tty->index = idx;
 	tty_line_name(driver, idx, tty->name);
-	tty->dev = tty_get_device(tty);
+	tty->dev = tty_find_device(tty_devnum(tty));
 
 	return tty;
 }
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 358a337af598..04d5f1213700 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -461,6 +461,7 @@ extern void tty_vhangup(struct tty_struct *tty);
 extern int tty_hung_up_p(struct file *filp);
 extern void do_SAK(struct tty_struct *tty);
 extern void __do_SAK(struct tty_struct *tty);
+extern struct device *tty_find_device(dev_t devt);
 extern void no_tty(void);
 extern void tty_flush_to_ldisc(struct tty_struct *tty);
 extern void tty_buffer_free_all(struct tty_port *port);