From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (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 86485426EC0 for ; Mon, 29 Jun 2026 14:44:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782744289; cv=none; b=lx0poNLLVUZjPgxH43xx+U0TZKPjO60dpMOCqoMJX6RCJzxJBVqU30BSryaMzlKtguy+H6WcKX3Q6eJ5ilgrIXtgGu/Ug0EVKaCTtfABgj4+90m4JXI+MU+TrQ5cq44JgeMGOqhpVhT5VtUmBIVlGVQF3FXlNaF0pxKQoyPDnz0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782744289; c=relaxed/simple; bh=rgpIHVCv/jG78fP6tu1dl2Qy9Ys1bGvoYAfVxN1Vrr4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=AwDy2+U6i2kBwT0xXIU+o83IZTpA42StSgfuZyBv4udCSFaLqT25jb/kBsz0OIoogKW3iykk+NJPAJqG/aw6edyQNtrBHOqrv6d0nRLCh7ZAbEEyA1/f8B5xDdYSt+a2AQPUAmF15uAV0CWV2matbWeOvwzac5bNkeDfKj88X6M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=gokLY0M0; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="gokLY0M0" Received: from killaraus.ideasonboard.com (2001-14ba-70f3-e800--a06.rev.dnainternet.fi [IPv6:2001:14ba:70f3:e800::a06]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 8DBE0E91; Mon, 29 Jun 2026 16:44:01 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1782744241; bh=rgpIHVCv/jG78fP6tu1dl2Qy9Ys1bGvoYAfVxN1Vrr4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gokLY0M0tPdapkigMuv4Uqg6nQoeAp9ooLReXpUXVg3B3IlLcUc15FrUa6tHeiqlN XFFu3bImhumtdCJX1OIyNvqmI5cXpP+Vyu/8E7LiH3H7pl79GTXJAoWrYLIka2vje4 m2AGTwxSCKAcReaJbpW3lBv0zCLhNN5BQxEZwwZM= Date: Mon, 29 Jun 2026 17:44:43 +0300 From: Laurent Pinchart To: Luca Ceresoli Cc: Maxime Ripard , Maarten Lankhorst , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Jonas Karlman , Jernej Skrabec , Inki Dae , Jagan Teki , Marek Szyprowski , Marek Vasut , Stefan Agner , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Hui Pu , Ian Ray , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 05/37] drm/display: bridge-connector: split code creating the connector to a subfunction Message-ID: <20260629144443.GA3106950@killaraus.ideasonboard.com> References: <20260519-drm-bridge-hotplug-v1-0-45e2bdb3dfb4@bootlin.com> <20260519-drm-bridge-hotplug-v1-5-45e2bdb3dfb4@bootlin.com> <20260608-mindful-heavy-frigatebird-be9faf@houat> <20260624-proud-unbiased-pony-ecc3c3@houat> <20260626-polite-hairy-perch-25e1aa@houat> <20260626-classy-nightingale-of-romance-1cacad@houat> 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-Disposition: inline In-Reply-To: On Fri, Jun 26, 2026 at 06:51:14PM +0200, Luca Ceresoli wrote: > On Fri Jun 26, 2026 at 4:38 PM CEST, Maxime Ripard wrote: > > On Fri, Jun 26, 2026 at 04:16:39PM +0200, Luca Ceresoli wrote: > >> On Fri Jun 26, 2026 at 12:09 PM CEST, Maxime Ripard wrote: > >> > On Wed, Jun 24, 2026 at 05:47:10PM +0200, Luca Ceresoli wrote: > >> >> On Wed Jun 24, 2026 at 1:41 PM CEST, Maxime Ripard wrote: > >> >> > On Fri, Jun 12, 2026 at 02:56:24PM +0200, Luca Ceresoli wrote: > >> >> >> On Mon Jun 8, 2026 at 1:40 PM CEST, Maxime Ripard wrote: > >> >> >> > On Tue, May 19, 2026 at 12:37:22PM +0200, Luca Ceresoli wrote: > >> >> >> >> In preparation to introduce bridge hotplug, split out from > >> >> >> >> drm_bridge_connector_init() the code adding the drm_connector into a > >> >> >> >> dedicated function. This will be needed to be able to add (and re-add) the > >> >> >> >> connector from different code paths. > >> >> >> > > >> >> >> > Same story here, explaining what you need later on that calls for that > >> >> >> > change would be nice. > >> >> >> > >> >> >> Here's a more verbose version: > >> >> >> > >> >> >> Currently drm_bridge_connector_init() does two things: > >> >> >> > >> >> >> * allocate and initialize the drm_bridge_connector > >> >> >> (which embeds a drm_connector) > >> >> >> * initialize and register the embedded drm_connector > >> >> >> > >> >> >> For bridge hotplug we need to separate these two actions: > >> >> >> > >> >> >> * the drm_connector needs to be added and removed at any time based on > >> >> >> hotplug events > >> >> >> * the drm_bridge_connector is designated to create and remove the > >> >> >> drm_connector, so it must be persistent for the card lifetime > >> >> >> > >> >> >> As the lifetimes of drm_bridge_connector and drm_connector become > >> >> >> different, we need to create them in different moments. > >> >> >> > >> >> >> In preparation to support that, split out from > >> >> >> drm_bridge_connector_init() the code adding the drm_connector into a > >> >> >> dedicated function. No functional changes, just moving code around for > >> >> >> now. A future commit will make the drm_connector be created based on > >> >> >> hotplug events. > >> >> >> > >> >> >> Looks good? > >> >> > > >> >> > The message itself, yes, thanks. > >> >> > > >> >> > However, I have questions now :) > >> >> > > >> >> > Do we really expect drm_bridge_connector to stick around when a bridge > >> >> > gets unplugged? If so, how does it cope with having, say, an HDMI > >> >> > connector, and then swapping out the hotplugged part for an LVDS one? > >> >> > Does the HDMI connector sticks around indefinitely? > >> >> > >> >> In your example, the HDMI drm_connector would be unregistered and put on > >> >> hotunplug. Its allocation will stick around until the last put but that's > >> >> quite irrelevant. Then, on plugging the LVDS addon, a new LVDS > >> >> drm_connector will be created and registered. > >> >> > >> >> > *Especially* if we're using overlays for this, I'd expect everything > >> >> > after the first hotplugged bridge to be destroyed, no? > >> >> > >> >> As said, it would be unregistered immediately but might be freed later on > >> >> if still refcounted. > >> >> > >> >> This is visible in patches 36+15, the path to follow is: > >> >> > >> >> drm_bridge_connector_handle_event(event = DRM_BRIDGE_DETACHED) [patch 36] > >> >> -> drm_bridge_connector_dynconn_release() [patch 15] > >> >> > >> >> Does this solve your concern? > >> > > >> > Not really, I'm talking about drm_bridge_connector. The fact that > >> > bridges are destroyed make sense to me. The fact that > >> > drm_bridge_connector sticks around doesn't. It's supposed to be a > >> > connector for bridges. If you don't have bridges because they got > >> > destroyed, and connector, drm_bridge_connector doesn't have a reason to > >> > exist anymore, unless it's drm_bridge_hotplug in a trench coat :) > >> > >> It is not a hotplug-bridge in a trench coat, no :) The code is clear about > >> this. > >> > >> I'd say with this series a "drm_bridge_connector" is just becoming > >> something more (perhaps something else too). Somewhat as "a drm_bridge is > >> either a bridge or something else". :) > >> > >> > >> But let's leave names aside for a moment. If just looking at the current > >> code, the drm_bridge_connector is "a handler, owned by the card/encoder and > >> having the same lifetime, which takes care of drm_connector > >> creation/destruction at card probe/removal". > >> > >> What we need now is just the same plug " and on hotplug events" appended. > >> > >> So in both cases there needs to be "a handler persitent with the card". > >> > >> Do we agree so far? > > > > Ish. If we go for that, then we need to update the name. > > drm_connector_manager? > drm_bridge_connector_manager? I'm fine with a rename. When developing drm_bridge_connector I've always envisioned it as code that manages the creation of a connector for a chain of bridges. In particular, the drm_bridge_connector object is *not* and has never been a bridge. Ideally all this should move to the DRM core and be transparent to drivers. Drivers could set a flag somewhere to opt-in for connectors managed by the DRM core. > > drm_bridge_connector for something that is neither a bridge or a > > connector is not great. > > > > But even then, I'm not even sure why we need to have that "manager" in > > the first place. You want to make bridges be aware if they are the last > > in the chain or not. I don't think bridges should be aware of whether or not they're the last one in the chain. > > Use that property in attach to either create a > > drm_bridge_connector instance if you're last, or attach the next bridge > > if you aren't. > > What? o_O > > Several encoder drivers have been painfully converted to create a > drm_bridge_connector. Now if the bridges start doing it themselves we > should go back to those encoder drivers and ditch all the > drm_bridge_connector from there? > > I must be missing something. Can you elaborate on this? -- Regards, Laurent Pinchart