From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-02.galae.net (smtpout-02.galae.net [185.246.84.56]) (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 B280620FA9C for ; Thu, 11 Sep 2025 15:40:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.246.84.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757605238; cv=none; b=lw6VzVv/241Sufk8IOOMMMRJeAG5vZwLZs7BHhFsIyHRiYOVf3cmbx0PBbvdZeGPjZSSRy5y+FQ8lEwcUQGJUdJ7Nwo01DByI6A9aElH84w7uvKHjjnJHMUDFivXsnWGQ6O2jePwphEHo8uPZu1YK55gKhiHIqjZh3kGb8IBoRY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757605238; c=relaxed/simple; bh=XLnEv1pwlrklnJ3MsTJZ2o/QFtDD8KtD9zWM46Z9OsQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=TSWfhTwUdC5RctRG1RwciYY2MfFVAZSO/Ky4VrhLWfG4hmpnf0H6Y+x8zftt46GDTIz3go3vTHKtPifkSKdoO37Xu0CkWtCAseLTxmmQZvdZ96CTOAZ5a0t8IV1qZYSD5E4zYd3aEV+NtltWogS+If963coUGPNEHKxJ5ilLH24= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=F1mBagPt; arc=none smtp.client-ip=185.246.84.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="F1mBagPt" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-02.galae.net (Postfix) with ESMTPS id 042951A0E06; Thu, 11 Sep 2025 15:40:34 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id BD07860630; Thu, 11 Sep 2025 15:40:33 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 3BB8B102F28D5; Thu, 11 Sep 2025 17:40:16 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1757605232; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:content-language:in-reply-to:references; bh=gPU5mGOIjO/p5kD0/6hvIG6AkAyidyKBOg8b+G3gqCE=; b=F1mBagPtjuHNR6RN6OCyE3XFYJ4wuqKkPBKbZx9H9XkA7uzWVv6NahKo9RPACt6XxbYhMy qudA+qXKzqTb6L5VN9MafUXr7rsPzTPRQup92B3rR2mOjoo31sSv52pmzU/23HE1g59kIO qzMTXknYlruxUaFZaGrXMl1fW9xwVM80ID+Y97Klta3lSLehY/Vlp/9db1ka3NkMBqFoHr q4uJ2saBIA2WEVp/fU0Km+UizSOSwR7DdWEFDLJ41e6I2UZ04W1EydkqZnWuPKoa2u7Scs +QMxt0TBMNo53dqZAZy/3Vt7oukKZqZvehIzreGl3TlVm8sMoODRV+kZS9FDiQ== Message-ID: Date: Thu, 11 Sep 2025 17:40:16 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/bridge: ite-it66121: Add drm_connector support To: Dmitry Baryshkov Cc: Maxime Ripard , Phong LE , Neil Armstrong , Andrzej Hajda , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Thomas Zimmermann , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, thomas.petazzoni@bootlin.com, miquel.raynal@bootlin.com, kory.maincent@bootlin.com, romain.gantois@bootlin.com, praneeth@ti.com, Aradhya Bhatia References: <20250909-it66121-fix-v1-1-bc79ca83df17@bootlin.com> <6164422a-6265-4726-8da5-68bb8eafb9e6@bootlin.com> <20250911-innocent-daffodil-macaque-797f13@houat> <012046ab-d866-4b3a-8c8a-e130bc2b9628@bootlin.com> <2l5kp4ojrcsg2apcpv7mzeeypwynecyfesenks6zzvnst3qkbt@4yhbosy2zhah> Content-Language: en-US From: Miguel Gazquez In-Reply-To: <2l5kp4ojrcsg2apcpv7mzeeypwynecyfesenks6zzvnst3qkbt@4yhbosy2zhah> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Last-TLS-Session-Version: TLSv1.3 Le 11/09/2025 à 15:09, Dmitry Baryshkov a écrit : > On Thu, Sep 11, 2025 at 02:49:59PM +0200, Miguel Gazquez wrote: >> >> >> Le 11/09/2025 à 11:50, Maxime Ripard a écrit : >>> On Thu, Sep 11, 2025 at 10:51:06AM +0200, Miguel Gazquez wrote: >>>> >>>> >>>> Le 10/09/2025 à 04:28, Dmitry Baryshkov a écrit : >>>>> On Tue, Sep 09, 2025 at 06:16:43PM +0200, Miguel Gazquez wrote: >>>>>> From: Aradhya Bhatia >>>>>> >>>>>> Add support for DRM connector and make the driver support the older >>>>>> format of attaching connectors onto the encoder->bridge->connector >>>>>> chain. >>>>>> This makes the driver compatible with display controller that only >>>>>> supports the old format. >>>>>> >>>>>> [Miguel Gazquez: Rebased + made driver work with or without >>>>>> DRM_BRIDGE_ATTACH_NO_CONNECTOR] >>>>> >>>>> What is the use case for not using DRM_BRIDGE_ATTACH_NO_CONNECTOR? >>>> >>>> Some display controller drivers (like the tilcdc) call drm_bridge_attach >>>> without DRM_BRIDGE_ATTACH_NO_CONNECTOR, so the bridge must support both with >>>> and without DRM_BRIDGE_ATTACH_NO_CONNECTOR to be compatible with all display >>>> controllers. >>> >>> I'd rather convert tilcdc to use DRM_BRIDGE_ATTACH_NO_CONNECTOR then. >> >> The problem is that doing that break devicetrees using the tilcdc and a >> bridge who doesn't support DRM_BRIDGE_ATTACH_NO_CONNECTOR (there are >> multiple bridges that don't support DRM_BRIDGE_ATTACH_NO_CONNECTOR), and if >> my understanding is correct breaking devicetrees is not allowed. > > How does it break devicetree? The drm_bridge_connector isn't a part of > DT. In the current situation, a board could have the tilcdc linked with a bridge that does not support DRM_BRIDGE_ATTACH_NO_CONNECTOR (for example, the analogix-anx6345) , and everything will work fine. If we convert the tilcdc to always use DRM_BRIDGE_ATTACH_NO_CONNECTOR, that same configuration will stop working. When I said "breaking devicetree" I meant that a devicetree describing this setup would no longer produce a working system, not that the DT files or bindings themselves are incorrect. I didn't find any upstream dts with this configuration, but maybe there is some out-of-tree dts which would be affected. As far as I understand, we should avoid that. On top of that, having the it66121 handle both cases makes it compatible with display controllers that don’t use DRM_BRIDGE_ATTACH_NO_CONNECTOR, which are still fairly common. -- Miguel Gazquez, Bootlin Embedded Linux and Kernel engineering https://bootlin.com