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 83C68F33807 for ; Tue, 17 Mar 2026 07:09:43 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C3BD010E34B; Tue, 17 Mar 2026 07:09:42 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="bjP/Zt2L"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.16]) by gabe.freedesktop.org (Postfix) with ESMTPS id 4923F10E34B for ; Tue, 17 Mar 2026 07:09:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1773731382; x=1805267382; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=ydlq9iZT7pXZv1FbMyd6TdpJuscB6ziFp9CUv6mPs+0=; b=bjP/Zt2Lh//2qa2CEU1Nzrspk5alNYzebs4rU4x52ftB/YwxNzc0yghl qzPZXOpGF/u+b77hWHd3psk6g9f4v0Sb2jbtAli/0bdZpRcph4cew1coH lczEfNgaK04hYf8mZNVUKrBOwaBn9nkxIKavH66oJ6aaUaGo1ZJlHd312 GhxlYkPVspGjKbDDhg24E9DJrvyfSknFU2FIXtaAIR/y82DTQepAJvIFi P8kEOfiRA/MGawqy+ZOEsIAHDpE2D7OCZzYQ0fQl+mTo+kDXfAEr40YoA KcxY519/3C0BkpEeiGDjEthIyzIg+AoCt+2/adlwPD3/9x7Gf95erhehh w==; X-CSE-ConnectionGUID: ufxEDksxTdKYMiRpuSwnZg== X-CSE-MsgGUID: viW74/NjQKS9hZQtiN1LQg== X-IronPort-AV: E=McAfee;i="6800,10657,11731"; a="62321764" X-IronPort-AV: E=Sophos;i="6.23,124,1770624000"; d="scan'208";a="62321764" Received: from fmviesa010.fm.intel.com ([10.60.135.150]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2026 00:09:41 -0700 X-CSE-ConnectionGUID: 2rl5YYinR4qS/QnWc+E1oA== X-CSE-MsgGUID: q2NQSYzSTIKk/IPjh2pz+w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,124,1770624000"; d="scan'208";a="218346746" Received: from pgcooper-mobl3.ger.corp.intel.com (HELO localhost) ([10.245.245.99]) by fmviesa010-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2026 00:09:30 -0700 Date: Tue, 17 Mar 2026 09:09:27 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Jani Nikula Cc: Thomas Zimmermann , Jammy Huang , Dave Airlie , Jocelyn Falempe , Maarten Lankhorst , Maxime Ripard , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/ast: DisplayPort edid supports 256 bytes Message-ID: References: <20260313-upstream_ast_dp_edid-v1-1-2a75b7c091b2@aspeedtech.com> 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 Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs Bertel Jungin Aukio 5, 02600 Espoo, Finland 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: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Mon, Mar 16, 2026 at 01:38:22PM +0200, Jani Nikula wrote: > On Mon, 16 Mar 2026, Thomas Zimmermann wrote: > > Hi Jammy > > > > Am 13.03.26 um 11:04 schrieb Jammy Huang: > >> DisplayPort supports edid at most 256 bytes. Thus, allow it to fetch > >> edid block 0 and 1. > >> > >> Signed-off-by: Jammy Huang > >> --- > >> ASPEED DisplayPort's EDID size can be 256 bytes at most. Thus, EDID > >> blocks fetched can be 0 and 1. > >> --- > >> drivers/gpu/drm/ast/ast_dp.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/drivers/gpu/drm/ast/ast_dp.c b/drivers/gpu/drm/ast/ast_dp.c > >> index 9d07dad358c..c938e1d6b1d 100644 > >> --- a/drivers/gpu/drm/ast/ast_dp.c > >> +++ b/drivers/gpu/drm/ast/ast_dp.c > >> @@ -88,7 +88,7 @@ static int ast_astdp_read_edid_block(void *data, u8 *buf, unsigned int block, si > >> int ret = 0; > >> unsigned int i; > >> > >> - if (block > 0) > >> + if (block > 1) > >> return -EIO; /* extension headers not supported */ > > > > But see the code at [1]. It clears the number of extensions to zero and > > updates the checksum accordingly. This is required to make the shortened > > EDID work with DRM. If you leave this as-is, it will still clear support > > for any extension in block 1. > > > > See the table 2.4 in the VESA EDID 1.4 standard for the semantics. For > > 1.3, if the number of blocks is >2, the first extensions is a 'block map > > of the extensions'. This is useless, as it's not a data extension in > > itself.  In 1.4, the block map is optional. That code should clear the > > EDID's number of extensions to 0 or 1, depending on whether there is a > > block map to be expected. > > I think long-term the goal should be for the kernel to not modify the > EDID, at all. I think as a short term goal it would be much better if all EDID mangling would be done by drm_edid.c rather than individual drivers. -- Ville Syrjälä Intel