platform/x86: acer-wmi: Ignore backlight event

On the Acer Nitro AN515-58, the event 4 - 0 is send by the ACPI
firmware when the backlight up/down keys are pressed. Ignore this
event to avoid spamming the kernel log with error messages, as the
acpi-video driver already handles brightness up/down events.

Reported-by: Bugaddr <Bugaddr@protonmail.com>
Closes: https://bugaddr.tech/posts/2025-11-16-debugging-the-acer-nitro-5-an515-58-fn-f10-keyboard-backlight-bug-on-linux/#wmi-interface-issues
Tested-by: Bugaddr <Bugaddr@protonmail.com>
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://patch.msgid.link/20251117155938.3030-1-W_Armin@gmx.de
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: Wer-Wolf

drivers/platform/x86/acer-wmi.c

@@ -102,6 +102,7 @@ MODULE_ALIAS("wmi:676AA15E-6A47-4D9F-A2CC-1E6D18D14026");
 
 enum acer_wmi_event_ids {
 	WMID_HOTKEY_EVENT = 0x1,
+	WMID_BACKLIGHT_EVENT = 0x4,
 	WMID_ACCEL_OR_KBD_DOCK_EVENT = 0x5,
 	WMID_GAMING_TURBO_KEY_EVENT = 0x7,
 	WMID_AC_EVENT = 0x8,
@@ -2369,6 +2370,9 @@ static void acer_wmi_notify(union acpi_object *obj, void *context)
 			sparse_keymap_report_event(acer_wmi_input_dev, scancode, 1, true);
 		}
 		break;
+	case WMID_BACKLIGHT_EVENT:
+		/* Already handled by acpi-video */
+		break;
 	case WMID_ACCEL_OR_KBD_DOCK_EVENT:
 		acer_gsensor_event();
 		acer_kbd_dock_event(&return_value);