serial: core: Move tty and serdev to be children of serial core port device

Let's move tty and serdev controller to be children of the serial core port
device. This way the runtime PM usage count of a child device propagates
to the serial hardware device.

The tty and serdev devices are associated with a specific serial port of
a serial hardware controller device, and we now have serial core hierarchy
of controllers and ports.

The tty device moves happily with just a change of the parent device and
update of device_find_child() handling. The serdev device init needs some
changes to separate the serial hardware controller device from the parent
device.

With this change the tty devices move under sysfs similar to this x86_64
qemu example of a diff of "find /sys -name ttyS*":

 /sys/class/tty/ttyS0
 /sys/class/tty/ttyS3
 /sys/class/tty/ttyS1
-/sys/devices/pnp0/00:04/tty/ttyS0
-/sys/devices/platform/serial8250/tty/ttyS2
-/sys/devices/platform/serial8250/tty/ttyS3
-/sys/devices/platform/serial8250/tty/ttyS1
+/sys/devices/pnp0/00:04/00:04:0/00:04:0.0/tty/ttyS0
+/sys/devices/platform/serial8250/serial8250:0/serial8250:0.3/tty/ttyS3
+/sys/devices/platform/serial8250/serial8250:0/serial8250:0.1/tty/ttyS1
+/sys/devices/platform/serial8250/serial8250:0/serial8250:0.2/tty/ttyS2

If a serdev device is used instead of a tty, it moves in a similar way.

Suggested-by: Johan Hovold <johan@kernel.org>
Cc: Maximilian Luz <luzmaximilian@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20231113080758.30346-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 9 insertions, 3 deletions

diff --git a/include/linux/serdev.h b/include/linux/serdev.h
index f5f97fa25e8a..0ebf53bb254f 100644
--- a/include/linux/serdev.h
+++ b/include/linux/serdev.h
@@ -99,12 +99,14 @@ struct serdev_controller_ops {
 /**
  * struct serdev_controller - interface to the serdev controller
  * @dev:	Driver model representation of the device.
+ * @host:	Serial port hardware controller device
  * @nr:		number identifier for this controller/bus.
  * @serdev:	Pointer to slave device for this controller.
  * @ops:	Controller operations.
  */
 struct serdev_controller {
 	struct device		dev;
+	struct device		*host;
 	unsigned int		nr;
 	struct serdev_device	*serdev;
 	const struct serdev_controller_ops *ops;
@@ -167,7 +169,9 @@ struct serdev_device *serdev_device_alloc(struct serdev_controller *);
 int serdev_device_add(struct serdev_device *);
 void serdev_device_remove(struct serdev_device *);
 
-struct serdev_controller *serdev_controller_alloc(struct device *, size_t);
+struct serdev_controller *serdev_controller_alloc(struct device *host,
+						  struct device *parent,
+						  size_t size);
 int serdev_controller_add(struct serdev_controller *);
 void serdev_controller_remove(struct serdev_controller *);
 
@@ -311,11 +315,13 @@ struct tty_driver;
 
 #ifdef CONFIG_SERIAL_DEV_CTRL_TTYPORT
 struct device *serdev_tty_port_register(struct tty_port *port,
+					struct device *host,
 					struct device *parent,
 					struct tty_driver *drv, int idx);
 int serdev_tty_port_unregister(struct tty_port *port);
 #else
 static inline struct device *serdev_tty_port_register(struct tty_port *port,
+					   struct device *host,
 					   struct device *parent,
 					   struct tty_driver *drv, int idx)
 {
diff --git a/include/linux/tty_port.h b/include/linux/tty_port.h
index 6b367eb17979..3276311a7f38 100644
--- a/include/linux/tty_port.h
+++ b/include/linux/tty_port.h
@@ -149,10 +149,10 @@ struct device *tty_port_register_device_attr(struct tty_port *port,
 		const struct attribute_group **attr_grp);
 struct device *tty_port_register_device_serdev(struct tty_port *port,
 		struct tty_driver *driver, unsigned index,
-		struct device *device);
+		struct device *host, struct device *parent);
 struct device *tty_port_register_device_attr_serdev(struct tty_port *port,
 		struct tty_driver *driver, unsigned index,
-		struct device *device, void *drvdata,
+		struct device *host, struct device *parent, void *drvdata,
 		const struct attribute_group **attr_grp);
 void tty_port_unregister_device(struct tty_port *port,
 		struct tty_driver *driver, unsigned index);