From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C1DA52192FA for ; Sat, 6 Jun 2026 19:28:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780774134; cv=none; b=FLV9ISnbkOfChARlskoE9CU6jCo3om4xPykY/1DBQGhBB2V89arhPRoqSxAq2gsSqYu2I8qDdxhleFH0nsTqIHBztXMFe9Ib6+YP5shHeCar9cMbJhqzdZgNGVrcLNO1vYyIqx7DFtqcGc50ISwJQgmw9CuupN41aTekzXf0V2I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780774134; c=relaxed/simple; bh=oyAPoepHl0yU5GomzmO2t7w+pifKz3OglIln4FNdk6Q=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: Content-Type:MIME-Version; b=FzFiDjgjIb0VFW6XvCD5RfxpUpLnlfwfksAr2GUjj6aPT0ZJZetalvrXF6BabbXXY+m7cUDGjmsWkiJSzrqw9IBh6q1RNY8cowMfanuM/n2AUz0RSVCdGAugYBIVoLd00tU1PJaRoqF4uGFustR2a/HOTd95YpZ28pO5xNiqR8g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=pQpkGKyJ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="pQpkGKyJ" Received: by smtp.kernel.org (Postfix) with ESMTPS id 65DBAC2BCC4 for ; Sat, 6 Jun 2026 19:28:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1780774134; bh=oyAPoepHl0yU5GomzmO2t7w+pifKz3OglIln4FNdk6Q=; h=From:To:Subject:Date:In-Reply-To:References:From; b=pQpkGKyJp23lBrFl3XBhHxjOKei8yy9HJ3MPVH9wtdN5P21KV2oP6BJw2TfIZJtYT A45irh/hV+duLSBXWHu+vNc9QN/5fUsoD/x3UmuFvhm7IFmGUQYn9DQnAhW5IEE4vY DIwbGMaKoWU2o9hNuNiGRoVMuqY1BX5b8eK/Mv+Jhn+klJyxkFq3tx4/zGd3H7oNDT u+fNZ4tNsCf5ZFjL4R/fcI9/z5gTfoX8yYhgCCtAIk4SDfoP0aUXHte6r99X6ActZF ydvx4D/2x69n+qWI+DRgMNT+fBZRUxLT8LXjtOww1c8VwJ0WQ+PsHGfaHiZiUjsyAn bi0r1zVqCDS5g== Received: by aws-us-west-2-korg-bugzilla-1.web.codeaurora.org (Postfix, from userid 48) id 42026C41613; Sat, 6 Jun 2026 19:28:54 +0000 (UTC) From: bugzilla-daemon@kernel.org To: platform-driver-x86@vger.kernel.org Subject: [Bug 221583] Lenovo 82KU: keyboard backlight works via Fn+Space but no kbd_backlight LED device exposed Date: Sat, 06 Jun 2026 19:28:54 +0000 X-Bugzilla-Reason: None X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: AssignedTo drivers_platform_x86@kernel-bugs.osdl.org X-Bugzilla-Product: Drivers X-Bugzilla-Component: Platform_x86 X-Bugzilla-Version: 2.5 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: i@rong.moe X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: drivers_platform_x86@kernel-bugs.osdl.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugzilla.kernel.org/ Auto-Submitted: auto-generated Precedence: bulk X-Mailing-List: platform-driver-x86@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 https://bugzilla.kernel.org/show_bug.cgi?id=3D221583 --- Comment #34 from Rong Zhang (i@rong.moe) --- Hmm, let's try some radical approaches. There is still a chance that some registers near 0x8A have something to do with the keyboard backlight brightness. 1. Set physical keyboard brightness to Low 2. Backup 0x8A: sudo busybox devmem 0xFE00D48A 8 3. sudo busybox devmem 0xFE00D42A 8 0x05 4. sudo busybox devmem 0xFE00D48A 8 0x00 5. sudo busybox devmem 0xFE00D42A 8 6. sudo busybox devmem 0xFE00D42A 8 0x05 7. sudo busybox devmem 0xFE00D48A 8 0xFF 8. sudo busybox devmem 0xFE00D42A 8 9. Restore the backup of 0x8A: sudo busybox devmem 0xFE00D48A 8 REPEAT the same procedure, but replace 0x8A with 0x8B. REPEAT with 0x8C. REPEAT with 0x8D. It could be dangerous as it massages a lot of bits. Be sure you have SSH ac= cess before trying this, as it could turn off the backlight of the screen. If massaging any of the four registers switches the brightness level to Hig= h, stop experimenting and restore the backup of the register value. If still no luck, you'd probably have to accept that it may not be possible= to set the brightness to High using software. I don't have any other idea, sig= h. Optimistically speaking, you can still switch between Off and Low using software and get OSD work for all three states. If you can take that, I thi= nk I can make a DSDT patch to achieve it. --=20 You may reply to this email to add a comment. You are receiving this mail because: You are watching the assignee of the bug.=