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 4D08AC433F5 for ; Wed, 16 Feb 2022 18:10:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237484AbiBPSKq (ORCPT ); Wed, 16 Feb 2022 13:10:46 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:49816 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237442AbiBPSKo (ORCPT ); Wed, 16 Feb 2022 13:10:44 -0500 Received: from mail-il1-x12d.google.com (mail-il1-x12d.google.com [IPv6:2607:f8b0:4864:20::12d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 011C32B0B1C for ; Wed, 16 Feb 2022 10:10:31 -0800 (PST) Received: by mail-il1-x12d.google.com with SMTP id f13so412438ilq.5 for ; Wed, 16 Feb 2022 10:10:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=dhg8ObNqJqU9MXgC8htbZHEYozTLZfTKNUE4M3ppPEQ=; b=X3YBCQPLYrjbSwdYieYTzfp5aHHmxsfeg3RTf4qZg0wFQ6+c9DxcKdaAJmOlc37Dsv CTdEpl0BzCTg87o7PF2lX4vr7saXRgNN4zH/iPLgcyLTPMZGhRdeuiUlyPMWzB1yffkQ L1SizYyjHV+Gfh5MA9OSmEyn4e1glalJ49FS0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=dhg8ObNqJqU9MXgC8htbZHEYozTLZfTKNUE4M3ppPEQ=; b=ueoZreMQ1k4DLXCSdUsHQZ2vn7iQ90WHddohi2Vq1KHLJ1thG89EZWEeea9H/TGV9M ROYRiWLJ4SIEXG3Yi1KqZ8+EnsY0nLM3g4GC00VKRsTkjD35DRpouz+AvaEjKwP0/NSs bZGpjcK48O8HEcx293p3joUkSf1TKR/FHNxsb9PB0u2I3fP2p2uSpJxA2s3Jl/UOwaHJ KynwkRCfaX7MPKvbKvxfKmGo9nyYIC/Xfws/HKQRmLGGSkXb5z8LO4M9cjwl2L1Yna75 GwffU0U3sQnYus/WlNKVABPZ8ZRLcS46qkrLqiVtcx1g3YS+gdQTk4OyCcq1MSOoaL3u 72Gg== X-Gm-Message-State: AOAM532fEBhwpXtWsen6Kc831Fb01OLRsJFx9ax9nMFYnKR24E5sAmYC AJ38lmhxggJ06X1Mjwq0KZPlWxYGJUiK9A== X-Google-Smtp-Source: ABdhPJyC1DggR2p3sQ6nOYoxwJqirAuyffugkK9LFHAKY1NBaAMwy5VIlMoO6PmDJDGXMNPwp8yW4w== X-Received: by 2002:a92:c269:0:b0:2be:795d:abb2 with SMTP id h9-20020a92c269000000b002be795dabb2mr2638878ild.46.1645035031221; Wed, 16 Feb 2022 10:10:31 -0800 (PST) Received: from mail-il1-f179.google.com (mail-il1-f179.google.com. [209.85.166.179]) by smtp.gmail.com with ESMTPSA id w4sm284536ilv.13.2022.02.16.10.10.28 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Feb 2022 10:10:29 -0800 (PST) Received: by mail-il1-f179.google.com with SMTP id z7so408410ilb.6 for ; Wed, 16 Feb 2022 10:10:28 -0800 (PST) X-Received: by 2002:a05:6e02:144f:b0:2bd:da3d:f50b with SMTP id p15-20020a056e02144f00b002bdda3df50bmr2425111ilo.165.1645035028535; Wed, 16 Feb 2022 10:10:28 -0800 (PST) MIME-Version: 1.0 References: <20211001144212.v2.1.I773a08785666ebb236917b0c8e6c05e3de471e75@changeid> In-Reply-To: From: Doug Anderson Date: Wed, 16 Feb 2022 10:10:16 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2] drm/bridge: analogix_dp: Grab runtime PM reference for DP-AUX To: Brian Norris Cc: Andrzej Hajda , Neil Armstrong , Sean Paul , Jonas Karlman , LKML , Jernej Skrabec , Laurent Pinchart , dri-devel , "open list:ARM/Rockchip SoC..." , "# 4.0+" , Tomeu Vizoso Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Tue, Feb 15, 2022 at 4:41 PM Brian Norris wrote: > > On Tue, Feb 15, 2022 at 3:46 PM Doug Anderson wrote: > > On Tue, Feb 15, 2022 at 2:52 PM Brian Norris wrote: > > > It still makes me wonder what the point > > > of the /dev/drm_dp_aux interface is though, because it seems like > > > you're pretty much destined to not have reliable operation through > > > that means. > > > > I can't say I have tons of history for those files. I seem to recall > > maybe someone using them to have userspace tweak the embedded > > backlight on some external DP connected panels? I think we also might > > use it in Chrome OS to update the firmware of panels (dunno if > > internal or external) in some cases too? I suspect that it works OK > > for certain situations but it's really not going to work in all > > cases... > > Yes, I believe I'm only submitting patches like this because fwupd > apparently likes to indiscriminately whack at dpaux devices: > https://github.com/fwupd/fwupd/tree/main/plugins/synaptics-mst#kernel-dp-aux-interface > > That seems like a bad idea. > > (We've already disabled that plugin on these systems, but it seems > wise not to leave the stumbling block here for the next time.) Yeah, it doesn't seem great. I guess it's _slightly_ less bad since it's for an external device. As I understand it, they never really turn off in the same way. It still feels like letting userspace indiscriminately whack at DP AUX registers isn't a great idea, though.