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 DC224C369AB for ; Tue, 15 Apr 2025 15:53:28 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2FC8F10E7E6; Tue, 15 Apr 2025 15:53:28 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="loWozUvt"; 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 7444610E7E6 for ; Tue, 15 Apr 2025 15:53:24 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 395F543852; Tue, 15 Apr 2025 15:53:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9DD30C4CEEB; Tue, 15 Apr 2025 15:53:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744732404; bh=W6Fvl1K7fKXPPKAM32Emk/h6KeYYqQ1cLu0Rj4bwCGg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=loWozUvtLWm+OMRpPsZeKzhrTKC8RzMXNRem4vneHdOVkFgXFByZoI48hukvZlBea DSWaMbcL/55v9cJrC5rRmiT9HaSDuBzC3fFJURZoCg5lri2u1W3DcOcVJCQFoQwese /wqcvN/bfwILlXJe5vq9sEXbEBlsjwPX1kkXX0FtJXAw6ak3iL3UKw7sDiYsNXLS9t TxQoh17aEYd+tUJ6yAqKA0tpeJxK1yxFje0GrPxIdcEYu5K6Tn08/DvKj0q1IZz4rf yuzwJ338JIO4NdEAiEqYxeMOGTYxIReEcMVYC7eCNU+jhSq6UWSK3v26ybiNm2+PAT v9zEXfPW/dOFQ== Date: Tue, 15 Apr 2025 16:53:19 +0100 From: Lee Jones To: Mario Limonciello Cc: mario.limonciello@amd.com, danielt@kernel.org, jingoohan1@gmail.com, Lennart Poettering , richard.purdie@linuxfoundation.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH] docs: backlight: Clarify `actual_brightness` Message-ID: <20250415155319.GZ372032@google.com> References: <20250408192729.4091391-1-superm1@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250408192729.4091391-1-superm1@kernel.org> 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" On Tue, 08 Apr 2025, Mario Limonciello wrote: > 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'. Which factors? Under what circumstances may the values not match? > Users: HAL > > What: /sys/class/backlight//max_brightness > -- > 2.43.0 > -- Lee Jones [李琼斯]