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 D2F85C25B75 for ; Wed, 15 May 2024 15:20:05 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0405410E5B5; Wed, 15 May 2024 15:20:05 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=linux.dev header.i=@linux.dev header.b="XFxgfMP3"; dkim-atps=neutral Received: from out-172.mta1.migadu.com (out-172.mta1.migadu.com [95.215.58.172]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0D4F610E4C2 for ; Wed, 15 May 2024 15:20:03 +0000 (UTC) Message-ID: <2c15c859-6b2b-4979-8317-698bf6cc430c@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1715786402; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EmD4Qw+Oobw3jODJD0oLXnLEGlKRGxu/voHJf2ZarqM=; b=XFxgfMP3HPxLUow/pJcgRdJr6LVhiCG33NNCO9WQPk36A8Xk1FCTVDOgqDzgP73sAq7Rk4 IWgSOsYKCKHgsAJlBedjYqWBPhMdG2LvTfrpV7ilPe5Ka7/0t4xvR9XL/UOM3+xFbMTcgv 8RNIRLe1w9ETbdzwSueiZzzVYiP+/7E= Date: Wed, 15 May 2024 23:19:58 +0800 MIME-Version: 1.0 Subject: Re: [PATCH 0/2] drm/bridge: Add 'struct device *' field to the drm_bridge structure To: Maxime Ripard Cc: Neil Armstrong , Dmitry Baryshkov , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20240514154045.309925-1-sui.jingfeng@linux.dev> <20240514-scarlet-corgi-of-efficiency-faf2bb@penduick> <20240515-fair-satisfied-myna-480dea@penduick> <20240515-copper-chimpanzee-of-fortitude-ff3dab@penduick> Content-Language: en-US, en-AU X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Sui Jingfeng In-Reply-To: <20240515-copper-chimpanzee-of-fortitude-ff3dab@penduick> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT 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" Hi, On 5/15/24 22:58, Maxime Ripard wrote: > On Wed, May 15, 2024 at 10:53:00PM +0800, Sui Jingfeng wrote: >> On 5/15/24 22:30, Maxime Ripard wrote: >>> On Wed, May 15, 2024 at 12:53:33AM +0800, Sui Jingfeng wrote: >>>> On 2024/5/15 00:22, Maxime Ripard wrote: >>>>> Hi, >>>>> >>>>> On Tue, May 14, 2024 at 11:40:43PM +0800, Sui Jingfeng wrote: >>>>>> Because a lot of implementations has already added it into their drived >>>>>> class, promote it into drm_bridge core may benifits a lot. drm bridge is >>>>>> a driver, it should know the underlying hardware entity. >>>>> Is there some actual benefits, or is it theoretical at this point? >>>> >>>> >>>> I think, DRM bridge drivers could remove the 'struct device *dev' >>>> member from their derived structure. Rely on the drm bridge core >>>> when they need the 'struct device *' pointer. >>> >>> Sure, but why do we need to do so? >>> >>> The other thread you had with Jani points out that it turns out that >>> things are more complicated than "every bridge driver has a struct >>> device anyway", it creates inconsistency in the API (bridges would have >>> a struct device, but not other entities), and it looks like there's no >>> use for it anyway. >>> >>> None of these things are deal-breaker by themselves, but if there's only >>> downsides and no upside, it's not clear to me why we should do it at all. >> >> It can reduce boilerplate. > > You're still using a conditional here. It's for safety reason, prevent NULL pointer dereference. drm bridge can be seen as either a software entity or a device driver. It's fine to pass NULL if specific KMS drivers intend to see drm bridge as a pure software entity, and for internal use only. Both use cases are valid. > > Maxime -- Best regards Sui