From: Hans de Goede <hdegoede@redhat.com>

Date: Fri, 17 Feb 2023 15:42:08 +0100

Subject: [PATCH] platform/x86: nvidia-wmi-ec-backlight: Add force module

 parameter

References: bsc#1012628

Patch-mainline: 6.2.1

Git-commit: 0d9bdd8a550170306c2021b8d6766c5343b870c2

commit 0d9bdd8a550170306c2021b8d6766c5343b870c2 upstream.

On some Lenovo Legion models, the backlight might be driven by either

one of nvidia_wmi_ec_backlight or amdgpu_bl0 at different times.

When the Nvidia WMI EC backlight interface reports the backlight is

controlled by the EC, the current backlight handling only registers

nvidia_wmi_ec_backlight (and registers no other backlight interfaces).

This hides (never registers) the amdgpu_bl0 interface, where as prior

to 6.1.4 users would have both nvidia_wmi_ec_backlight and amdgpu_bl0

and could work around things in userspace.

Add a force module parameter which can be used with acpi_backlight=native

to restore the old behavior as a workound (for now) by passing:

"acpi_backlight=native nvidia-wmi-ec-backlight.force=1"

Fixes: 8d0ca287fd8c ("platform/x86: nvidia-wmi-ec-backlight: Use acpi_video_get_backlight_type()")

Link: https://bugzilla.kernel.org/show_bug.cgi?id=217026

Cc: stable@vger.kernel.org

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Reviewed-by: Daniel Dadap <ddadap@nvidia.com>

Link: https://lore.kernel.org/r/20230217144208.5721-1-hdegoede@redhat.com

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Jiri Slaby <jslaby@suse.cz>

---

 drivers/platform/x86/nvidia-wmi-ec-backlight.c | 6 +++++-

 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/nvidia-wmi-ec-backlight.c b/drivers/platform/x86/nvidia-wmi-ec-backlight.c

index baccdf65..1b572c90 100644

--- a/drivers/platform/x86/nvidia-wmi-ec-backlight.c

+++ b/drivers/platform/x86/nvidia-wmi-ec-backlight.c

@@ -12,6 +12,10 @@

 #include <linux/wmi.h>

 #include <acpi/video.h>

+static bool force;

+module_param(force, bool, 0444);

+MODULE_PARM_DESC(force, "Force loading (disable acpi_backlight=xxx checks");

+

 /**

  * wmi_brightness_notify() - helper function for calling WMI-wrapped ACPI method

  * @w:    Pointer to the struct wmi_device identified by %WMI_BRIGHTNESS_GUID

@@ -91,7 +95,7 @@ static int nvidia_wmi_ec_backlight_probe(struct wmi_device *wdev, const void *ct

 	int ret;

 	/* drivers/acpi/video_detect.c also checks that SOURCE == EC */

-	if (acpi_video_get_backlight_type() != acpi_backlight_nvidia_wmi_ec)

+	if (!force && acpi_video_get_backlight_type() != acpi_backlight_nvidia_wmi_ec)

 		return -ENODEV;

 	/*

-- 

2.35.3