[PATCH v3 5/7] platform/x86: thinkpad_acpi: Skip LED suspend/resume on auto-mode machines

[Qiling Zhu <kmatzkaczor244@gmail.com>]

On machines whose EC supports the auto mode (MLCG bit 20) the firmware
takes care of the keyboard backlight across suspend by itself: on a
ThinkPad X1 Carbon Gen 14 it turns the backlight off on suspend and
restores the previous level on resume for the manual levels, and keeps
auto mode across suspend; after hibernation from auto mode the
backlight comes back off.

Skip led_classdev_suspend() and led_classdev_resume() entirely on those
machines: the LED core no longer enters the suspended state, which also
removes the window in which userspace writes and pending
set_brightness work would race against a suspended LED.

Machines without auto-mode support keep the existing behavior.

Signed-off-by: Qiling Zhu <kmatzkaczor244@gmail.com>
---
 drivers/platform/x86/lenovo/thinkpad_acpi.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/platform/x86/lenovo/thinkpad_acpi.c b/drivers/platform/x86/lenovo/thinkpad_acpi.c
index 681b340a1..f9e2d324d 100644
--- a/drivers/platform/x86/lenovo/thinkpad_acpi.c
+++ b/drivers/platform/x86/lenovo/thinkpad_acpi.c
@@ -5317,6 +5317,14 @@ static void kbdlight_suspend(void)
 	if (!tp_features.kbdlight)
 		return;
 
+	/*
+	 * On machines with auto-mode support the firmware takes care of
+	 * the keyboard backlight across suspend by itself; keep the LED
+	 * core out of it.
+	 */
+	if (tp_features.kbdlight_auto)
+		return;
+
 	led_cdev = &tpacpi_led_kbdlight.led_classdev;
 	led_update_brightness(led_cdev);
 	led_classdev_suspend(led_cdev);
@@ -5327,6 +5335,9 @@ static void kbdlight_resume(void)
 	if (!tp_features.kbdlight)
 		return;
 
+	if (tp_features.kbdlight_auto)
+		return;
+
 	led_classdev_resume(&tpacpi_led_kbdlight.led_classdev);
 }
 
-- 
2.56.1