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 B12A3FA373F for ; Mon, 24 Oct 2022 22:40:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230158AbiJXWkF (ORCPT ); Mon, 24 Oct 2022 18:40:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43472 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232420AbiJXWje (ORCPT ); Mon, 24 Oct 2022 18:39:34 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DEE19491E7 for ; Mon, 24 Oct 2022 14:03:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666645299; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Pm5HJkjYWeeX/qs3JDehVtgKORU0AuoMo2twQDux5eA=; b=Pkjw5YuhCqBjYoycjA4MeeQMG10d0rPQlFzVQ/n6tKqfw6xDHSWnsMzPkeqJdorUiJTMYs 68hZF34d6WnmSIIcZcq252r8frSNU2ZJQgMjPGncTPOcycd8m61vPvpc4bVrD7K+YEmPN/ +PsLce+ZnuNKhdAmp+4PWMg+v//328s= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-191-yR3jpZ-sOIOwG_A6Z8LFjw-1; Mon, 24 Oct 2022 09:24:01 -0400 X-MC-Unique: yR3jpZ-sOIOwG_A6Z8LFjw-1 Received: by mail-ed1-f70.google.com with SMTP id z7-20020a05640235c700b0045d3841ccf2so9610408edc.9 for ; Mon, 24 Oct 2022 06:24:01 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Pm5HJkjYWeeX/qs3JDehVtgKORU0AuoMo2twQDux5eA=; b=TvBB1fkKfHRmG6OtuXQAktrqPcx5d2eTB5m9OQJdUspHNs9EMHd9t+aBjIT74KTqbS NqHR7l5HTAQxpTqEj6M3AbGzcpFPBPr0GxLiFFgsjmucIJ3xioPP1+K0A7kzIm2M+kaU dwqv7FtdFP1dut/q2pgqM3uooEYvEr8L6YKC57A8fos+WVvBwXRVMYTey7fcDY9GQy65 leXCYd/GZ6eIBoZYqyMgpWswriU1FoR5PjRbmNqlB714NdRVZTNdREmMKUwW5VYGkLoz lJ74bbukvM7Mc88kCnhbVa66VRL68Kgg1WD9iDZ2uxodKy+3XYshU+HHZmnNhaZ7Scae 0anQ== X-Gm-Message-State: ACrzQf33lyE+y9g6WKYvX93I2JkQzrA8dneTy/5ZTi7Rqt27xaKPBpSQ 6IO7eGq8gjuzJfMAzjYJCmmyN+XMjTmc7sHoJRI/QqQ8fyrN0UaUmHzFLQHRqnUJcPy+/069fQQ 1bHxR2UNuhhBQWZgbQwm41g== X-Received: by 2002:a17:907:75c4:b0:78e:176e:f62e with SMTP id jl4-20020a17090775c400b0078e176ef62emr27636755ejc.736.1666617840052; Mon, 24 Oct 2022 06:24:00 -0700 (PDT) X-Google-Smtp-Source: AMsMyM6nRpfOUd7fXfaQxZAoL/YNjVZG4I1hOQtgleKwhNKXvtlVx02RUh+6naoowPVHW1NVhRqxQg== X-Received: by 2002:a17:906:8a6a:b0:79e:2efe:e0 with SMTP id hy10-20020a1709068a6a00b0079e2efe00e0mr12680099ejc.401.1666617828842; Mon, 24 Oct 2022 06:23:48 -0700 (PDT) Received: from [10.40.98.142] ([78.108.130.194]) by smtp.gmail.com with ESMTPSA id b27-20020a17090630db00b0073dbaeb50f6sm15619252ejb.169.2022.10.24.06.23.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Oct 2022 06:23:48 -0700 (PDT) Message-ID: <84d86b61-7694-2e22-3593-b11b3ce33cf8@redhat.com> Date: Mon, 24 Oct 2022 15:23:46 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.1 Subject: Re: [PATCH 00/22] Fallback to native backlight Content-Language: en-US To: =?UTF-8?Q?Pali_Roh=c3=a1r?= , Akihiko Odaki Cc: 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 References: <20221024113513.5205-1-akihiko.odaki@daynix.com> <746e5cc6-516f-8f69-9d4b-8fe237de8fd6@redhat.com> <20221024131451.lvkesdg3kvyvbi7n@pali> From: Hans de Goede In-Reply-To: <20221024131451.lvkesdg3kvyvbi7n@pali> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org Hi, On 10/24/22 15:14, Pali Rohár wrote: > 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). Right and that is just one example of laptops which can register both vendor + native backlight devices, which is why this whole series is a bad idea. Regards, Hans > 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).