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 109CEC61DC4 for ; Thu, 27 Aug 2026 14:17:10 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 411B310F082; Thu, 27 Aug 2026 14:17:09 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="LOOuDyD1"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id DD92310F082 for ; Thu, 27 Aug 2026 14:17:08 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 98C2A41639; Thu, 27 Aug 2026 14:17:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0A01B1F000E9; Thu, 27 Aug 2026 14:17:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787840228; bh=SRS6X6TXw6Tr+PFBiZcsPHGo5nRK4IWPTb7UQu+FNwU=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=LOOuDyD1bld19rGBu8oHAHMiweAT/Te66dh5B+NbY34f+CmejOjHIq9nTHRXW/uEZ D4b1L46WgQJnV0e4gnFWE7mszOSJ/PMQPzId1vHY6PWFj+S5/66sKQJpEN/jglF65J E2BzvdctpNl7LKh331P3vgzpvAPozUc3FFQlMZpuSXtl/MV0bqXubI8MnyqKVqGEYg yiIqoMnZXTWiabr4DFJiBexZKXlgWCXIPXfZ6ThRad0UYimgqlgiDCTcd9y5v2PVvP Ov+jNbQTZ3lKRizZWwuezlN+mFrChWxAZEq0C4AjOW+Kw2GewlJu4iO+7yVd6VKENg DHrK4LzA99R0g== Date: Thu, 27 Aug 2026 16:17:04 +0200 From: Maxime Ripard To: Luca Ceresoli Cc: Maarten Lankhorst , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Jessica Zhang , Linus Walleij , Inki Dae , Jagan Teki , Marek Szyprowski , Dmitry Baryshkov , Hui Pu , Ian Ray , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 04/11] drm/panel: merge the drm_kms_helper module into the drm module Message-ID: References: <20260824-cuddly-aardwark-of-reward-0d93d4@houat> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha384; protocol="application/pgp-signature"; boundary="3h6vkmrdieos4f6d" Content-Disposition: inline In-Reply-To: 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" --3h6vkmrdieos4f6d Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH 04/11] drm/panel: merge the drm_kms_helper module into the drm module MIME-Version: 1.0 On Mon, Aug 24, 2026 at 04:16:02PM +0200, Luca Ceresoli wrote: > Hi Maxime, >=20 > On Mon Aug 24, 2026 at 9:48 AM CEST, Maxime Ripard wrote: > > On Mon, Aug 17, 2026 at 02:27:58PM +0200, Luca Ceresoli wrote: > >> On Mon Aug 17, 2026 at 10:31 AM CEST, Maxime Ripard wrote: > >> > On Fri, Aug 14, 2026 at 04:05:52PM +0200, Luca Ceresoli wrote: > >> >> Work is in progress to make every drm_panel automatically create a > >> >> panel_bridge [0][1]. > >> >> > >> >> This requires the panel code to call the drm_panel_bridge APIs. How= ever > >> >> this would create a circular dependency loop on modular builds: > >> >> > >> >> __devm_drm_panel_alloc() [drm] > >> >> -> drm_panel_bridge_add() [drm_kms_helper] > >> >> -> drm_bridge.c APIs [drm] > >> >> > >> >> Moving just the panel_brige.o file from [drm_kms_helper] to [drm] d= oes not > >> >> work because the panel bridge code uses the drm_atomic_helper and > >> >> drm_probe_helper which add further dependencies on symbols in the > >> >> [drm_kms_helper] module. > >> >> > >> >> So take a simple approach, and move the entire drm_kms_helper into = the > >> >> [drm] module. > >> >> > >> >> Link: https://lore.kernel.org/all/emuj2innmp6zmzd7pyakqzjqpdzhly6qf= hakya3ydwmd63pl26@5jwxaidpikjw/ [0] > >> >> Link: https://lore.kernel.org/lkml/20250206-hotplug-drm-bridge-v6-8= -9d6f2c9c3058@bootlin.com/ [1] > >> >> Signed-off-by: Luca Ceresoli > >> > > >> > So, that's not an option. However, why do we need drm_panel_bridge_a= dd() > >> > after this work is done? If we want to create a bridge for every pan= el, > >> > then the bridge implementation can live in drm_panel.c, which is par= t of > >> > the drm module. > >> > > >> > And we'd essentially move drm_panel_bridge into drm_panel.c, and mak= e it > >> > private. > >> > >> Yes in theory, but the panel_bridge code uses other parts of the > >> drm_kms_helper module: drm_atomic_helper and drm_probe_helper, maybe m= ore, > >> so we'd have to move them into the drm module too. > > > > Ah, right. What would happen if we were doing it the other way around > > then? Move drm_panel out of the main drm module? >=20 > Into the drm_kms_helper module? >=20 > I had a look and did some experiments and I found at least one user in th= e drm > module calling a drm_panel API, and guess who: >=20 > drm_of_find_panel_or_bridge() (in drm_of.c, drm module) > -> calls of_drm_find_panel (in drm_panel.c, drm_kms_helper module) >=20 > Based on our discussion after patch 3, I'm not sure > drm_of_find_panel_or_bridge() will disappear soon. If it doesn't, I guess > we can try to move drm_of_find_panel_or_bridge() into bridge/panel.c which > is in the drm_kms_helper module (and from drm_of.h info > drm_bridge.h?). That however might trigger build failures for drivers whi= ch > currently don't select DRM_KMS_HELPER and which would have to select it. >=20 > I'll give it a try, and if I see major drawbacks I will get back to moving > all the drm_kms_helper code into the main drm module. No, I meant into its own module. Do we have any dependency from the main drm module into drm_panel? Maxime --3h6vkmrdieos4f6d Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJUEABMJAB0WIQTkHFbLp4ejekA/qfgnX84Zoj2+dgUCapBG3AAKCRAnX84Zoj2+ dncAAX9e0Le80mECcRvZjSFwfKDsJn14yX3qpt61zpnr4XCT7oYutU6uDr1R3/aq BtDoNW8BgKN0pJx0d4WvMJowi4FKM9HLeXIVZOanNJQlHbCV551rvrJJHQkcpP9u wtO4YWM9TA== =RS0G -----END PGP SIGNATURE----- --3h6vkmrdieos4f6d--