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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 D45D4C282DE for ; Thu, 13 Mar 2025 12:18:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Subject:Cc:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=JhXUy51c9HOiF2dM0ShdmXt1Njr+UGlAd/NPatt3K0Q=; b=nXB9iyJm15tXTK8jWnP7AoWOZn YxM53qaZvQ9xFL6SAijbHXB7MGjc65NDm5zZ5mm8fJzG3x6fqFFHnb+1UaOYWTx4DZJyiyWZuIIvt 68eJB/5S/F1++HrQoGKLUPYnqwyaX+XHfGCHCF62nutVJEim3iqJLSovLyKK/GTIQgwPi44rqSxVH tSnvpGRj5Rpg1w0597gKpnyFlcbvBHU0IfVexr6BdWL0y+eK7KvdYNp4+WJNm38J6tSC/RASBlVkB 2pufgWCsDQYn110ucFRIam2LxnFYfyv4u+3pxCnM5C7aRwTQf4If0CfYiO01WRkvHOlslugio/WA7 MLXyKajg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tshVn-0000000BDVO-3GoT; Thu, 13 Mar 2025 12:18:08 +0000 Received: from relay6-d.mail.gandi.net ([2001:4b98:dc4:8::226]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tshBU-0000000B9RZ-1n6x for linux-arm-kernel@lists.infradead.org; Thu, 13 Mar 2025 11:57:10 +0000 Received: by mail.gandi.net (Postfix) with ESMTPSA id EA15B43290; Thu, 13 Mar 2025 11:56:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1741867023; 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=JhXUy51c9HOiF2dM0ShdmXt1Njr+UGlAd/NPatt3K0Q=; b=QwnyFTZYHlEK0gM8ijiyd15oLuWJmqqgsBCfTj5dOwO8Ny2Zx0aUjpStJFhwkMDmaPvmo0 Qk5FqkGvQlzKhqGEUhWczOpYH6r86aXQxq8KCQ69Kst4cIgUREiVQdPyh3JNUoFAtUzEdL oKBoPnqi4f8o+vBx3ceJ1my6wLrWoqSi7EGg9P9cvzKphYMEMGc2C79bpBU7P1aeyzGVky DCXwUhNvJFJmGTnswNa1DLdZWbdRwwbhMiKnrSAkj1ypGAcr3qs+sgFGzBZMXQIYI0jMaG GiT7iStHOIXg9NqorQxWoG/e1Fh95b4KKxXc4/BNXFp25JWtuZoVtP1q9dlmdQ== Date: Thu, 13 Mar 2025 12:56:56 +0100 From: Luca Ceresoli To: Maxime Ripard Cc: Simona Vetter , Inki Dae , Jagan Teki , Marek Szyprowski , Catalin Marinas , Will Deacon , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Daniel Thompson , Andrzej Hajda , Jonathan Corbet , Sam Ravnborg , Boris Brezillon , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea , Jessica Zhang , Paul Kocialkowski , Dmitry Baryshkov , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Thomas Zimmermann , David Airlie , =?UTF-8?B?SGVy?= =?UTF-8?B?dsOp?= Codina , Thomas Petazzoni , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Paul Kocialkowski Subject: Re: [PATCH v6 14/26] drm/bridge: add support for refcounted DRM bridges Message-ID: <20250313125656.70448d09@booty> In-Reply-To: <20250207-ingenious-daffodil-dugong-51be57@houat> References: <20250206-hotplug-drm-bridge-v6-0-9d6f2c9c3058@bootlin.com> <20250206-hotplug-drm-bridge-v6-14-9d6f2c9c3058@bootlin.com> <20250207-ingenious-daffodil-dugong-51be57@houat> Organization: Bootlin X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-GND-State: clean X-GND-Score: -100 X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgdduvdejkeekucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuifetpfffkfdpucggtfgfnhhsuhgsshgtrhhisggvnecuuegrihhlohhuthemuceftddunecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpeffhffvvefukfgjfhhoofggtgfgsehtjeertdertddvnecuhfhrohhmpefnuhgtrgcuvegvrhgvshholhhiuceolhhutggrrdgtvghrvghsohhlihessghoohhtlhhinhdrtghomheqnecuggftrfgrthhtvghrnheptdeljeejuddvudetffdtudelfedugfduledtueffuedufefgudegkeegtdeihedunecuffhomhgrihhnpehkvghrnhgvlhdrohhrghdpsghoohhtlhhinhdrtghomhenucfkphepvdgrtddvmeeijedtmedvtddvtdemvggrtddumegrtddtvdemudgsrgejmeegkehfjeemudeltgehnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehinhgvthepvdgrtddvmeeijedtmedvtddvtdemvggrtddumegrtddtvdemudgsrgejmeegkehfjeemudeltgehpdhhvghlohepsghoohhthidpmhgrihhlfhhrohhmpehluhgtrgdrtggvrhgvshholhhisegsohhothhlihhnrdgtohhmpdhnsggprhgtphhtthhopeefjedprhgtphhtthhopehmrhhiphgrrhgusehkvghrnhgvlhdrohhrghdprhgtphhtthhopehsihhmohhnrgesfhhffihllhdrtghhpdhrtghpthhtohepihhnkhhirdgurggvsehsrghmshhun hhgrdgtohhmpdhrtghpthhtohepjhgrghgrnhesrghmrghruhhlrghsohhluhhtihhonhhsrdgtohhmpdhrtghpthhtohepmhdrshiihihprhhofihskhhisehsrghmshhunhhgrdgtohhmpdhrtghpthhtoheptggrthgrlhhinhdrmhgrrhhinhgrshesrghrmhdrtghomhdprhgtphhtthhopeifihhllheskhgvrhhnvghlrdhorhhgpdhrtghpthhtohepshhhrgifnhhguhhosehkvghrnhgvlhdrohhrgh X-GND-Sasl: luca.ceresoli@bootlin.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250313_045708_916766_D04D6EA2 X-CRM114-Status: GOOD ( 29.76 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hello Maxime, On Fri, 7 Feb 2025 12:47:51 +0100 Maxime Ripard wrote: > Hi, > > On Thu, Feb 06, 2025 at 07:14:29PM +0100, Luca Ceresoli wrote: > > DRM bridges are currently considered as a fixed element of a DRM card, and > > thus their lifetime is assumed to extend for as long as the card > > exists. New use cases, such as hot-pluggable hardware with video bridges, > > require DRM bridges to be added and removed to a DRM card without tearing > > the card down. This is possible for connectors already (used by DP MST), so > > add this possibility to DRM bridges as well. > > > > Implementation is based on drm_connector_init() as far as it makes sense, > > and differs when it doesn't. A difference is that bridges are not exposed > > to userspace, hence struct drm_bridge does not embed a struct > > drm_mode_object which would provide the refcount. Instead we add to struct > > drm_bridge a refcount field (we don't need other struct drm_mode_object > > fields here) and instead of using the drm_mode_object_*() functions we > > reimplement from those functions the few lines that drm_bridge needs for > > refcounting. > > > > Also add a new devm_drm_bridge_alloc() macro to allocate a new refcounted > > bridge. > > > > Signed-off-by: Luca Ceresoli > > So, a couple of general comments: > > - I've said it a couple of times already, but I really think you're > making it harder than necessary for you here. This (and only this!) > should be the very first series you should be pushing. The rest can > only ever work if that work goes through, and it's already hard enough > as it is. So, split that patch into a series of its own, get that > merged, and then we will be able to deal with panels conversion and > whatever. That's even more true with panels since there's ongoing work > that will make it easier for you too. So the best thing here is > probably to wait. > > - This patch really needs to be split into several patches, something > along the lines of: > > + Creating devm_drm_bridge_alloc() > + Adding refcounting > + Taking the references in all the needed places > + Converting a bunch of drivers After reading Anusha's "[PATCH RFC 0/2] drm/panel: Refcounted panel allocation" [0] I think I need a clarification about the 4 steps you had outlined in the above quoted text. Are you suggesting those are four _series_, and you'd want to see a series only creating devm_drm_bridge_alloc() as a first step, similarly to Anusha's work? That was not my understanding so far, and so I've been working on a series containing all 4 items, and it's growing very long due to item 3 needing to touch many dozen drivers which need to put a bridge (many are identical oneliner patches though). Luca [0] https://lore.kernel.org/all/20250312-drm-panel-v1-0-e99cd69f6136@redhat.com/ -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com