platform/x86: ideapad-laptop: introduce a generic notification chain

There are several cases where a notification chain can simplify Lenovo
WMI drivers.

Add a generic notification chain into ideapad-laptop.
Signed-off-by: Gergo Koteles <soyer@irl.hu>
Link: https://lore.kernel.org/r/c5a43efae8a32bd034c3d19c0a686941347575a7.1721898747.git.soyer@irl.huReviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

drivers/platform/x86/ideapad-laptop.c

@@ -1592,6 +1592,39 @@ static void ideapad_sync_touchpad_state(struct ideapad_private *priv, bool send_
 	priv->r_touchpad_val = value;
 }
 
+static int ideapad_laptop_nb_notify(struct notifier_block *nb,
+				    unsigned long action, void *data)
+{
+	switch (action) {
+	}
+
+	return 0;
+}
+
+static struct notifier_block ideapad_laptop_notifier = {
+	.notifier_call = ideapad_laptop_nb_notify,
+};
+
+static BLOCKING_NOTIFIER_HEAD(ideapad_laptop_chain_head);
+
+int ideapad_laptop_register_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&ideapad_laptop_chain_head, nb);
+}
+EXPORT_SYMBOL_NS_GPL(ideapad_laptop_register_notifier, IDEAPAD_LAPTOP);
+
+int ideapad_laptop_unregister_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&ideapad_laptop_chain_head, nb);
+}
+EXPORT_SYMBOL_NS_GPL(ideapad_laptop_unregister_notifier, IDEAPAD_LAPTOP);
+
+void ideapad_laptop_call_notifier(unsigned long action, void *data)
+{
+	blocking_notifier_call_chain(&ideapad_laptop_chain_head, action, data);
+}
+EXPORT_SYMBOL_NS_GPL(ideapad_laptop_call_notifier, IDEAPAD_LAPTOP);
+
 static void ideapad_acpi_notify(acpi_handle handle, u32 event, void *data)
 {
 	struct ideapad_private *priv = data;
@@ -1974,6 +2007,8 @@ static int ideapad_acpi_add(struct platform_device *pdev)
 	if (err)
 		goto shared_init_failed;
 
+	ideapad_laptop_register_notifier(&ideapad_laptop_notifier);
+
 	return 0;
 
 shared_init_failed:
@@ -2006,6 +2041,8 @@ static void ideapad_acpi_remove(struct platform_device *pdev)
 	struct ideapad_private *priv = dev_get_drvdata(&pdev->dev);
 	int i;
 
+	ideapad_laptop_unregister_notifier(&ideapad_laptop_notifier);
+
 	ideapad_shared_exit(priv);
 
 	acpi_remove_notify_handler(priv->adev->handle,

drivers/platform/x86/ideapad-laptop.h

@@ -12,6 +12,11 @@
 #include <linux/acpi.h>
 #include <linux/jiffies.h>
 #include <linux/errno.h>
+#include <linux/notifier.h>
+
+int ideapad_laptop_register_notifier(struct notifier_block *nb);
+int ideapad_laptop_unregister_notifier(struct notifier_block *nb);
+void ideapad_laptop_call_notifier(unsigned long action, void *data);
 
 enum {
 	VPCCMD_R_VPC1 = 0x10,