[Bug] Lenovo LOQ 15ARP9: _BCM evaluation failed (-22), backlight control broken

Hello, I am writing to report a backlight control issue on a Lenovo LOQ 15ARP9 laptop (AMD Ryzen + NVIDIA GPU using the open-source nouveau driver). Display brightness adjustment is completely non-functional. During boot, the kernel outputs the following error: [ 5.209088] nouveau 0000:01:00.0: drm: [DRM/0000000b:kmsOutp] [BL_GET level:0] (ret:-22) After discussing this with Karol Herbst (nouveau maintainer), it was pointed out that this is an ACPI subsystem/firmware issue rather than a driver bug. I have created a detailed bug report on Bugzilla containing all necessary debugging details (full dmesg logs and acpidump): https://bugzilla.kernel.org/show_bug.cgi?id=221859 Please let me know if any additional tests or information are needed to help resolve this.