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>

1 files changed, 9 insertions, 7 deletions

diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 63c125250961..ef72d2e4b928 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -171,7 +171,8 @@ EXPORT_SYMBOL_GPL(tty_port_register_device_attr);
  * @port: tty_port of the device
  * @driver: tty_driver for this device
  * @index: index of the tty
- * @device: parent if exists, otherwise NULL
+ * @host: serial port hardware device
+ * @parent: parent if exists, otherwise NULL
  * @drvdata: driver data for the device
  * @attr_grp: attribute group for the device
  *
@@ -180,20 +181,20 @@ EXPORT_SYMBOL_GPL(tty_port_register_device_attr);
  */
 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)
 {
 	struct device *dev;
 
 	tty_port_link_device(port, driver, index);
 
-	dev = serdev_tty_port_register(port, device, driver, index);
+	dev = serdev_tty_port_register(port, host, parent, driver, index);
 	if (PTR_ERR(dev) != -ENODEV) {
 		/* Skip creating cdev if we registered a serdev device */
 		return dev;
 	}
 
-	return tty_register_device_attr(driver, index, device, drvdata,
+	return tty_register_device_attr(driver, index, parent, drvdata,
 			attr_grp);
 }
 EXPORT_SYMBOL_GPL(tty_port_register_device_attr_serdev);
@@ -203,17 +204,18 @@ EXPORT_SYMBOL_GPL(tty_port_register_device_attr_serdev);
  * @port: tty_port of the device
  * @driver: tty_driver for this device
  * @index: index of the tty
- * @device: parent if exists, otherwise NULL
+ * @host: serial port hardware controller device
+ * @parent: parent if exists, otherwise NULL
  *
  * Register a serdev or tty device depending on if the parent device has any
  * defined serdev clients or not.
  */
 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)
 {
 	return tty_port_register_device_attr_serdev(port, driver, index,
-			device, NULL, NULL);
+			host, parent, NULL, NULL);
 }
 EXPORT_SYMBOL_GPL(tty_port_register_device_serdev);