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 X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2F7B8C433E1 for ; Mon, 24 Aug 2020 15:46:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 07597205CB for ; Mon, 24 Aug 2020 15:46:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727877AbgHXPql (ORCPT ); Mon, 24 Aug 2020 11:46:41 -0400 Received: from mga01.intel.com ([192.55.52.88]:54490 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726473AbgHXPqd (ORCPT ); Mon, 24 Aug 2020 11:46:33 -0400 IronPort-SDR: wzWOcaVaAOoJkM4BHPp4A/WFfMBqAVBahyEEq57b47V7F3plUW6oHwrv7RweijURoyLU4KQLSt 92ar8YSvHcTw== X-IronPort-AV: E=McAfee;i="6000,8403,9722"; a="173967474" X-IronPort-AV: E=Sophos;i="5.76,349,1592895600"; d="scan'208";a="173967474" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Aug 2020 08:46:33 -0700 IronPort-SDR: i7xHs3m94j+1i3c9HXOILdk4W9Z9gJTr27gBBejZQ8KOIcu6cMQhKqui/tQzcYc+PagzTKe9ht Q57pUhHYNWEw== X-IronPort-AV: E=Sophos;i="5.76,349,1592895600"; d="scan'208";a="443257291" Received: from ideak-desk.fi.intel.com ([10.237.68.141]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Aug 2020 08:46:29 -0700 Date: Mon, 24 Aug 2020 18:46:26 +0300 From: Imre Deak To: Lyude Paul Cc: Sean Paul , Ville Syrjala , nouveau@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Thomas Zimmermann , David Airlie , Lucas De Marchi , open list , Gwan-gyeong Mun , Manasi Navare , Uma Shankar , Rodrigo Vivi , =?iso-8859-1?Q?Jos=E9?= Roberto de Souza , Wambui Karuga Subject: Re: [RFC 13/20] drm/i915/dp: Extract drm_dp_downstream_read_info() Message-ID: <20200824154626.GA19658@ideak-desk.fi.intel.com> Reply-To: imre.deak@intel.com References: <20200811200457.134743-1-lyude@redhat.com> <20200811200457.134743-14-lyude@redhat.com> <20200819151547.GB46474@art_vandelay> <4d74a74aefcd8d0ea048b70252efda18820bc911.camel@redhat.com> <20200820223754.GA17451@ideak-desk.fi.intel.com> <597b83ace909f97bfefbe15ffbb0370c2101ff0f.camel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <597b83ace909f97bfefbe15ffbb0370c2101ff0f.camel@redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 21, 2020 at 01:43:39PM -0400, Lyude Paul wrote: > [...] > > The wording is a bit unclear, but as I understand the Standard only > > calls for the above: > > > > """ > > A DP upstream device shall read the capability from DPCD Addresses 00080h > > through 00083h. A DP Branch device with multiple DFPs shall report the > > detailed > > capability information of the lowest DFP number to which a downstream device > > is connected, consistent with the DisplayID or legacy EDID access routing > > policy > > of an SST-only DP Branch device as described in Section 2.1.4.1. > > """ > > So-I saw this too, but notice the use of the language "A /DP Branch/ device with > multiple DFPs shall report the detailed…". This makes me think it's implying > that this is a requirement for MSTBs and not SST sinks, just a guess. Not sure either. The above could also refer to an SST branch device with multiple DFPs (for instance a DP Replicator branch device). --Imre