platform/x86: serdev_helpers: Add get_serdev_controller_from_parent() helper

The x86-android-tablets code needs to be able to get a serdev_controller
device from a PCI parent, rather then by the ACPI HID+UID of the parent,
because on some tablets the UARTs are enumerated as PCI devices instead
of ACPI devices.

Split the code to walk the device hierarchy to find the serdev_controller
from its parents out into a get_serdev_controller_from_parent() helper
so that the x86-android-tablets code can re-use it.

Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20241204204227.95757-5-hdegoede@redhat.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

1 files changed, 34 insertions, 26 deletions

diff --git a/drivers/platform/x86/serdev_helpers.h b/drivers/platform/x86/serdev_helpers.h
index 3bc7fd8e1e19..57eac75805e2 100644
--- a/drivers/platform/x86/serdev_helpers.h
+++ b/drivers/platform/x86/serdev_helpers.h
@@ -22,32 +22,14 @@
 #include <linux/string.h>
 
 static inline struct device *
-get_serdev_controller(const char *serial_ctrl_hid,
-		      const char *serial_ctrl_uid,
-		      int serial_ctrl_port,
-		      const char *serdev_ctrl_name)
+get_serdev_controller_from_parent(struct device *ctrl_dev,
+				  int serial_ctrl_port,
+				  const char *serdev_ctrl_name)
 {
-	struct device *ctrl_dev, *child;
-	struct acpi_device *ctrl_adev;
+	struct device *child;
 	char name[32];
 	int i;
 
-	ctrl_adev = acpi_dev_get_first_match_dev(serial_ctrl_hid, serial_ctrl_uid, -1);
-	if (!ctrl_adev) {
-		pr_err("error could not get %s/%s serial-ctrl adev\n",
-		       serial_ctrl_hid, serial_ctrl_uid ?: "*");
-		return ERR_PTR(-ENODEV);
-	}
-
-	/* get_first_physical_node() returns a weak ref */
-	ctrl_dev = get_device(acpi_get_first_physical_node(ctrl_adev));
-	if (!ctrl_dev) {
-		pr_err("error could not get %s/%s serial-ctrl physical node\n",
-		       serial_ctrl_hid, serial_ctrl_uid ?: "*");
-		ctrl_dev = ERR_PTR(-ENODEV);
-		goto put_ctrl_adev;
-	}
-
 	/* Walk host -> uart-ctrl -> port -> serdev-ctrl */
 	for (i = 0; i < 3; i++) {
 		switch (i) {
@@ -67,14 +49,40 @@ get_serdev_controller(const char *serial_ctrl_hid,
 		put_device(ctrl_dev);
 		if (!child) {
 			pr_err("error could not find '%s' device\n", name);
-			ctrl_dev = ERR_PTR(-ENODEV);
-			goto put_ctrl_adev;
+			return ERR_PTR(-ENODEV);
 		}
 
 		ctrl_dev = child;
 	}
 
-put_ctrl_adev:
-	acpi_dev_put(ctrl_adev);
 	return ctrl_dev;
 }
+
+static inline struct device *
+get_serdev_controller(const char *serial_ctrl_hid,
+		      const char *serial_ctrl_uid,
+		      int serial_ctrl_port,
+		      const char *serdev_ctrl_name)
+{
+	struct acpi_device *adev;
+	struct device *parent;
+
+	adev = acpi_dev_get_first_match_dev(serial_ctrl_hid, serial_ctrl_uid, -1);
+	if (!adev) {
+		pr_err("error could not get %s/%s serial-ctrl adev\n",
+		       serial_ctrl_hid, serial_ctrl_uid ?: "*");
+		return ERR_PTR(-ENODEV);
+	}
+
+	/* get_first_physical_node() returns a weak ref */
+	parent = get_device(acpi_get_first_physical_node(adev));
+	acpi_dev_put(adev);
+	if (!parent) {
+		pr_err("error could not get %s/%s serial-ctrl physical node\n",
+		       serial_ctrl_hid, serial_ctrl_uid ?: "*");
+		return ERR_PTR(-ENODEV);
+	}
+
+	/* This puts our reference on parent and returns a ref on the ctrl */
+	return get_serdev_controller_from_parent(parent, serial_ctrl_port, serdev_ctrl_name);
+}