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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9E0B0FA3740 for ; Mon, 24 Oct 2022 20:16:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234159AbiJXUQ4 (ORCPT ); Mon, 24 Oct 2022 16:16:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33992 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234135AbiJXUQV (ORCPT ); Mon, 24 Oct 2022 16:16:21 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7E00C150F88; Mon, 24 Oct 2022 11:33:43 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C0FA1612E7; Mon, 24 Oct 2022 13:14:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F11F4C433C1; Mon, 24 Oct 2022 13:14:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666617295; bh=3nE0pujKjkKrAG3Zlhw1YeJuPRfB3mFezLZb6lzLCGA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LMm2+6OBEsQawTDmuHx79XkDRpx8g9QS54i0VAgQtCk02UkomS95/vMkOooCKFRX3 xxQEe24yv/tDtsQYrTGmzauMv0Jh6zHqana1EL/TBHlmO6GXulViaDuIlAEYGkafKP kqE4fIBr817hQoEx/xF9wYtGawey5ywjjoX7MjRMntvcbUYm0BK0RPqRrLUuuXw2Nk nhWxKTcWwM9VEt4aM7KgAIT39FftcsQukjfpyyfLMkVVk5XzPzt3H5NCVm2IIV71GR WEwDHsAVQ/xfBG0zYbWT3h7jEZyT/78B/fc3OPRLq/euFmv9sbHup10WXUReRUbepL 1J6fTEisi4WTg== Received: by pali.im (Postfix) id 060EE82F; Mon, 24 Oct 2022 15:14:51 +0200 (CEST) Date: Mon, 24 Oct 2022 15:14:51 +0200 From: Pali =?utf-8?B?Um9ow6Fy?= To: Akihiko Odaki Cc: Hans de Goede , David Airlie , Daniel Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Jonathan Corbet , "Rafael J. Wysocki" , Len Brown , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , "Lee, Chun-Yi" , Mark Gross , Corentin Chary , Cezary Jackiewicz , Matthew Garrett , Jonathan Woithe , Ike Panhc , Daniel Dadap , Kenneth Chan , Mattia Dongili , Henrique de Moraes Holschuh , Azael Avalos , Lee Jones , Daniel Thompson , Jingoo Han , Helge Deller , Robert Moore , dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, intel-gfx@lists.freedesktop.org, platform-driver-x86@vger.kernel.org, acpi4asus-user@lists.sourceforge.net, ibm-acpi-devel@lists.sourceforge.net, linux-fbdev@vger.kernel.org, devel@acpica.org Subject: Re: [PATCH 00/22] Fallback to native backlight Message-ID: <20221024131451.lvkesdg3kvyvbi7n@pali> References: <20221024113513.5205-1-akihiko.odaki@daynix.com> <746e5cc6-516f-8f69-9d4b-8fe237de8fd6@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Monday 24 October 2022 21:58:57 Akihiko Odaki wrote: > Regarding the second limitation, I don't even understand the difference > between vendor and native. My guess is that a vendor backlight device uses > vendor-specific ACPI interface, and a native one directly uses hardware > registers. If my guess is correct, the difference between vendor and native > does not imply that both of them are likely to exist at the same time. As > the conclusion, there is no more motivation to try to de-duplicate the > vendor/native combination than to try to de-duplicate combination of devices > with a single type. Hello! I just want to point one thing. On some Dell laptops there are 3 different ways (= 3 different APIs) how to control display backlight. There is ACPI driver (uses ACPI), GPU/DRM driver (i915.ko; uses directly HW) and platform vendor driver (dell-laptop.ko; uses vendor BIOS or firmware API). Just every driver has different pre-calculated scaling values. So sometimes user wants to choose different driver just because it allows to set backlight level with "better" granularity. Registering all 3 device drivers is bad as user does not want to see 3 display panels and forcing registration of specific one without runtime option is also bad (some of those drivers do not have to be suitable or has worse granularity as other).