From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1B8DAC36010 for ; Tue, 8 Apr 2025 19:27:46 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 86BC310E283; Tue, 8 Apr 2025 19:27:45 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="LRm0gUHH"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id E2E2E10E283 for ; Tue, 8 Apr 2025 19:27:43 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 47579451A1; Tue, 8 Apr 2025 19:27:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 182EDC4CEE5; Tue, 8 Apr 2025 19:27:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744140461; bh=1nJbBDFh6oitUst+PBO9XClnNvX8SJl/gbJ4B7oS8wM=; h=From:To:Cc:Subject:Date:From; b=LRm0gUHHhLBoNfRJaYuqHacI8HdGAQ6ymvgxS5NRfprxFQaX/TJvYVYNspc0R88u9 a4tVowMx1OVGGPKnlR5bUs4Bw79hBoVaiLyKj5AXqW75lpnCdA1hfjbJwpmz12ziKx qYzaLkRGxvNwGAh0vW71RdyG4ThsPrT69CZdwwW2CpEH2DFhx0V+25agijfnGzaDau eTD9+3QRimifJdbTjddf/YEpnXoylzN49P8kRAW0TBYtsuK8LPxWlByeSsPzHqqaS0 VZXDcw0NpDlNDFNQ4W0Oyf8G1mlAZa6lv909n0hHHfBBq/aRlv4vb0RTNUTlxed7gF eBOwYZEQa4Lbg== From: Mario Limonciello To: mario.limonciello@amd.com, lee@kernel.org, danielt@kernel.org, jingoohan1@gmail.com Cc: Lennart Poettering , richard.purdie@linuxfoundation.org, dri-devel@lists.freedesktop.org Subject: [PATCH] docs: backlight: Clarify `actual_brightness` Date: Tue, 8 Apr 2025 14:27:28 -0500 Message-ID: <20250408192729.4091391-1-superm1@kernel.org> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" From: Mario Limonciello Currently userspace software systemd treats `brightness` and `actual_brightness` identically due to a bug found in an out of tree driver. This however causes problems for in-tree drivers that use brightness to report user requested `brightness` and `actual_brightness` to report what the hardware actually has programmed. Clarify the documentation to match the behavior described in commit 6ca017658b1f9 ("[PATCH] backlight: Backlight Class Improvements"). Cc: Lennart Poettering Cc: richard.purdie@linuxfoundation.org Link: https://github.com/systemd/systemd/pull/36881 Signed-off-by: Mario Limonciello --- Documentation/ABI/stable/sysfs-class-backlight | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/Documentation/ABI/stable/sysfs-class-backlight b/Documentation/ABI/stable/sysfs-class-backlight index 6102d6bebdf9a..909cacde85041 100644 --- a/Documentation/ABI/stable/sysfs-class-backlight +++ b/Documentation/ABI/stable/sysfs-class-backlight @@ -26,7 +26,9 @@ Date: March 2006 KernelVersion: 2.6.17 Contact: Richard Purdie Description: - Show the actual brightness by querying the hardware. + Show the actual brightness by querying the hardware. This + takes into account other factors besides the value programmed + for 'brightness' and may not match the value in 'brightness'. Users: HAL What: /sys/class/backlight//max_brightness -- 2.43.0