[RFC 02/13] acpi/x86: s2idle: add support for Display Off and Display On callbacks

[Antheas Kapenekakis <lkml@antheas.dev>]

The Display Off and Display On firmware notifications are meant to signify
the system entering a state where the user is not actively interacting
with it (i.e., in Windows this state is called "Screen Off" and the
system enters it once it turns the screen off e.g., due to inactivity).

Currently, these functions are called within the suspend sequence, which
causes issues when these notifications interact with e.g., a USB device
and makes them unable to be called as part of the screen turning off.

This patch adds a set of callbacks to allow calling the Display On/Off
notifications outside of the suspend/resume path.

Co-developed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
---
 include/linux/suspend.h |  2 ++
 kernel/power/suspend.c  | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index da6ebca3ff77..57c083754e8b 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -132,6 +132,7 @@ struct platform_suspend_ops {
 };
 
 struct platform_s2idle_ops {
+	int (*display_off)(void);
 	int (*begin)(void);
 	int (*prepare)(void);
 	int (*prepare_late)(void);
@@ -140,6 +141,7 @@ struct platform_s2idle_ops {
 	void (*restore_early)(void);
 	void (*restore)(void);
 	void (*end)(void);
+	int (*display_on)(void);
 };
 
 #ifdef CONFIG_SUSPEND
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 09f8397bae15..cded6b9b439b 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -254,6 +254,16 @@ static bool sleep_state_supported(suspend_state_t state)
 	       (valid_state(state) && !cxl_mem_active());
 }
 
+static int platform_standby_display_off(void)
+{
+	return s2idle_ops && s2idle_ops->display_off ? s2idle_ops->display_off() : 0;
+}
+
+static int platform_standby_display_on(void)
+{
+	return s2idle_ops && s2idle_ops->display_on ? s2idle_ops->display_on() : 0;
+}
+
 static int platform_suspend_prepare(suspend_state_t state)
 {
 	return state != PM_SUSPEND_TO_IDLE && suspend_ops->prepare ?
-- 
2.47.0