From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 82187366043 for ; Mon, 16 Mar 2026 11:38:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773661111; cv=none; b=OZ6tVOgXmqVAQSSlcr6N4hzG7YmLDzMMj8eg+XasE9P8YKThrcOOEuhYL8nnR/7JWoopipMQSX33btIbB01QTR/3AFdOzv8FiqrH1CeXa8VQe7jUJuR/9X7+3BRUcNdOrCkHUwPdtc24Wq4XyCtlnBTUN1Ev7pr3Z4D1RfV1xCk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773661111; c=relaxed/simple; bh=+R6gKdN94J8gAlUgGk+V1A9HkdVF8gpG1K0Cax4/Y0w=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=eFbw9AfhFBn4SUXRIF4dgRhgR6Rn6Dv08w8AAZQh82pN5XlsXC4E7tB+3CG8OSZsrHhZLgzjyPzudV/k0APvN0UcVJMQZW4vsgmXkg49ZY1MxcEkg+8K0VKEWwTF+u6EApZk+owFs343sEubT3W1TRrEqvXh0ziVyeps90W3BMI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=LZhTCYGU; arc=none smtp.client-ip=192.198.163.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="LZhTCYGU" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1773661109; x=1805197109; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version:content-transfer-encoding; bh=+R6gKdN94J8gAlUgGk+V1A9HkdVF8gpG1K0Cax4/Y0w=; b=LZhTCYGU/GqF7IWyAfxrZRCke+YxWGfUVBmA0gySiz699GtxiXJEyArL RRp617iBSKiE8Msw4AwbwFqfK1cBpjb9ZOQ0RQaFi2pGrPctb1FcNF6MV gjby/Jatp6o37v0k0oJYm2B4vF/iJOtylpqkUs9BaCYlhME7MFI9EFf4K 8l7YKS+0G1gn4A7edH7SfyAQ9ejM7V3OlpiaA1Lf3vwjn3ym7DKFR4cZX p5lBqgdBXcQ7Cvfv6h1o4M1CcAAqCg+RgyCAswrta45M9oWrBwm+oZgRS 0MD0B6hS6ls7J5quvoYxc0krwuzbfDxzx2Prbl0pKIFbl+gigbRBtAJlQ g==; X-CSE-ConnectionGUID: eWlBnuokQbaDa1WH7+f3hw== X-CSE-MsgGUID: gizKeCSnTUaq5yj6FwR4Uw== X-IronPort-AV: E=McAfee;i="6800,10657,11730"; a="74591255" X-IronPort-AV: E=Sophos;i="6.23,124,1770624000"; d="scan'208";a="74591255" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by fmvoesa111.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Mar 2026 04:38:29 -0700 X-CSE-ConnectionGUID: B5rwkWNARhqGLnnb8/lkgw== X-CSE-MsgGUID: Dd2TWJwGR1WJ+oRLVEh7mw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,124,1770624000"; d="scan'208";a="217728754" Received: from mjarzebo-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.246.238]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Mar 2026 04:38:25 -0700 From: Jani Nikula To: Thomas Zimmermann , Jammy Huang , Dave Airlie , Jocelyn Falempe , Maarten Lankhorst , Maxime Ripard , David Airlie , Simona Vetter Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/ast: DisplayPort edid supports 256 bytes In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs Bertel Jungin Aukio 5, 02600 Espoo, Finland References: <20260313-upstream_ast_dp_edid-v1-1-2a75b7c091b2@aspeedtech.com> Date: Mon, 16 Mar 2026 13:38:22 +0200 Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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 *b= uf, unsigned int block, si >> int ret =3D 0; >> unsigned int i; >>=20=20=20 >> - 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=20 > updates the checksum accordingly. This is required to make the shortened= =20 > EDID work with DRM. If you leave this as-is, it will still clear support= =20 > for any extension in block 1. > > See the table 2.4 in the VESA EDID 1.4 standard for the semantics. For=20 > 1.3, if the number of blocks is >2, the first extensions is a 'block map= =20 > of the extensions'. This is useless, as it's not a data extension in=20 > itself.=C2=A0 In 1.4, the block map is optional. That code should clear t= he=20 > EDID's number of extensions to 0 or 1, depending on whether there is a=20 > block map to be expected. I think long-term the goal should be for the kernel to not modify the EDID, at all. BR, Jani. > > Best regards > Thomas > > [1]=20 > https://elixir.bootlin.com/linux/v6.19.8/source/drivers/gpu/drm/ast/ast_d= p.c#L157 > >>=20=20=20 >> /* >> >> --- >> base-commit: 5ee8dbf54602dc340d6235b1d6aa17c0f283f48c >> change-id: 20260313-upstream_ast_dp_edid-5fe6adf7ad36 >> >> Best regards, --=20 Jani Nikula, Intel