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 100FCC25B48 for ; Tue, 24 Oct 2023 13:03:34 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 332AA10E398; Tue, 24 Oct 2023 13:03:33 +0000 (UTC) Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.65]) by gabe.freedesktop.org (Postfix) with ESMTPS id 9007710E398; Tue, 24 Oct 2023 13:03:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1698152611; x=1729688611; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=uOVs+S/Vm5KdP4XzRWN/fe7nQcMLrO0eNOaeBiJ8gw0=; b=nSxDdqrrhEgu4Mf8MzSwajaFVh6QQED1OR4bn7rexdOp3P0S7FH6iyvO 5Qk1ifIge10u7FJeN03wenx9G+429olDtlaHYmWCOwouG++7KRd4jLt07 d0leQzhzsuGmr1RIUwRlmj+TVJb6syKTEQjic/mutcTDFlP6ox6zKuLpg PrpME/U6dLJg6nupFsKQR8y/XohHDnbx+7FuNU/ecdMgAkLQ/i0Sfa51W Xs0SGBD8PG/IJUXZJgFqlJtD1qQ15uLk8xb4cH3ckJ/a0lGGYTEVs5hnk Rrbc0h2qEkvKBl7pL4oFeHjKplrqJ6pUlI5LW85TiJ+UvJbbAA5Vt1Y4s w==; X-IronPort-AV: E=McAfee;i="6600,9927,10873"; a="390925202" X-IronPort-AV: E=Sophos;i="6.03,247,1694761200"; d="scan'208";a="390925202" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Oct 2023 06:03:31 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10873"; a="875063991" X-IronPort-AV: E=Sophos;i="6.03,247,1694761200"; d="scan'208";a="875063991" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.74]) by fmsmga002.fm.intel.com with SMTP; 24 Oct 2023 06:03:26 -0700 Received: by stinkbox (sSMTP sendmail emulation); Tue, 24 Oct 2023 16:03:27 +0300 Date: Tue, 24 Oct 2023 16:03:27 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Simon Ser Subject: Re: [PATCH] drm/doc: describe PATH format for DP MST Message-ID: References: <20231023203629.198109-1-contact@emersion.fr> <20231024103604.6dd7f6d5@eldfell> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Patchwork-Hint: comment 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: , Cc: Dmitry Baryshkov , Daniel Vetter , Pekka Paalanen , dri-devel@lists.freedesktop.org, wayland-devel@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, Oct 24, 2023 at 09:03:22AM +0000, Simon Ser wrote: > On Tuesday, October 24th, 2023 at 09:36, Pekka Paalanen wrote: > > > Are DP MST port numbers guaranteed to be tied to the physical hardware > > configuration (e.g. how cables are connected) and therefore stable > > across reboots? What about stable across kernel upgrades? > > > > If I knew that, I could perhaps manufacture a stable identifier in > > userspace by replacing the parent connector ID with a stable connector > > designator. > > Hm, my assumption is that these are stable, but maybe that's also wrong? > Ville, Dmitry, do you know whether the DP MST port numbers are > guaranteed stable across reboots when retaining the exact same hardware > configuration (not the software, maybe the user upgraded the kernel)? I suspect in practice those should remain the same as long as the topology didn't change, but I don't think there's anything in the DP spec that actually guarantees that (eg. some branch device could in theory reshuffle its port numbers on a whim). But there is no stable identifier for the corresponding SST connector anyway so I don't know what you would even do with stable port numbers. -- Ville Syrjälä Intel