From e9cf4d9b9a6fdb1df6401a59f5ac5d24006bfeae Mon Sep 17 00:00:00 2001
From: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Date: Mon, 24 Oct 2022 17:12:10 +0300
Subject: [PATCH] ACPI: video: Fix missing native backlight on Chromebooks
Git-commit: e9cf4d9b9a6fdb1df6401a59f5ac5d24006bfeae
Patch-mainline: v6.1-rc3
References: bsc#1206843

Chromebooks don't have backlight in ACPI table, they suppose to use
native backlight in this case. Check presence of the CrOS embedded
controller ACPI device and prefer the native backlight if EC found.

Suggested-by: Hans de Goede <hdegoede@redhat.com>
Fixes: 2600bfa3df99 ("ACPI: video: Add acpi_video_backlight_use_native() helper")
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20221024141210.67784-1-dmitry.osipenko@collabora.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/acpi/video_detect.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/drivers/acpi/video_detect.c
+++ b/drivers/acpi/video_detect.c
@@ -558,6 +558,11 @@ static int acpi_video_backlight_notify(s
 	return NOTIFY_OK;
 }
 
+static bool google_cros_ec_present(void)
+{
+	return acpi_dev_found("GOOG0004");
+}
+
 /*
  * Determine which type of backlight interface to use on this system,
  * First check cmdline, then dmi quirks, then do autodetect.
@@ -618,6 +623,13 @@ static enum acpi_backlight_type __acpi_v
 			return acpi_backlight_video;
 	}
 
+	/*
+	 * Chromebooks that don't have backlight handle in ACPI table
+	 * are supposed to use native backlight if it's available.
+	 */
+	if (google_cros_ec_present() && native_available)
+		return acpi_backlight_native;
+
 	/* No ACPI video (old hw), use vendor specific fw methods. */
 	return acpi_backlight_vendor;
 }