From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 63B4636CC63; Tue, 26 Aug 2025 15:48:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756223301; cv=none; b=IrMBkqe4X8ygU2V3PMu3DbsujKaNcHEJtz9ABXcV+sF7kXNuGTJjgs7SbrRv2Ij3TlNK4g/1qQ9ChoPLA4s5MwLI5c2UKJni3ebXGiiZ5n66+Vl106pYIjjNPUgXlX3f8q3o0EjEiqqDBMdqjDOAH4GOp+DZZhcJtj8QTabIX1E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756223301; c=relaxed/simple; bh=b8FPl/vsVw5JNumARcRZVHO1eLeE0zNGP8ZNm5DfGWI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=AonG9Jqztv9zlIGpKIUdm9J11jmPOPQ0TPdFN2akVJypNEdxQfu36WS6a6OHWl5b6VgFt9ONP5mZUwWrZMiMIihDqHGgSmbN1BtAIA6pxcxHiLzdH4bJvyiIBftNAxO8fD+Lw5dW2//qXF2Wq2OW1ydRNB6xpBkjOM06iMKbwLI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cBpUZwwJ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cBpUZwwJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D1E1C4CEF1; Tue, 26 Aug 2025 15:48:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756223300; bh=b8FPl/vsVw5JNumARcRZVHO1eLeE0zNGP8ZNm5DfGWI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cBpUZwwJwkflKJ0/vGcmpkC8DliLFLjpny0HUmG2Ln346CiBilgYH94HOREACj5jF Eq+XapbP4mc3qqOBbKqJAOA0njYw2EK8+6zfRSA0eWXfO/SnsO8pThLIrOhMQixQZd XHTps7BStTJKDCTVj8vOn5Gy/oHQabqqNoH1MEnvwi5qkv97UYldOWhQP3PUn5/9Lm OHy0yblKZsp109frfTjXxEUXfzNX/BWGVXFCAq2cHizxUwV7oPc2+wbbiLb4kwDlOc 9FKAQoMjqXrG9GwaCG+g+UxkSz4WB1qo0ykVddH858/C+LLN/pLzUJQA3YX3ce1Yuk 4SOasopz6FeBw== Date: Tue, 26 Aug 2025 17:48:18 +0200 From: "mripard@kernel.org" To: "Kandpal, Suraj" Cc: Dmitry Baryshkov , "liviu.dudau@arm.com" , Laurent Pinchart , "kernel-list@raspberrypi.com" , "amd-gfx@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" , "linux-renesas-soc@vger.kernel.org" , "linux-arm-msm@vger.kernel.org" , "freedreno@lists.freedesktop.org" , "dri-devel@lists.freedesktop.org" , "intel-xe@lists.freedesktop.org" , "intel-gfx@lists.freedesktop.org" , "Nautiyal, Ankit K" , "Murthy, Arun R" , "Shankar, Uma" , "Nikula, Jani" , "harry.wentland@amd.com" , "siqueira@igalia.com" , "alexander.deucher@amd.com" , "christian.koenig@amd.com" , "airlied@gmail.com" , "simona@ffwll.ch" , "maarten.lankhorst@linux.intel.com" , "robin.clark@oss.qualcomm.com" , "abhinav.kumar@linux.dev" , "tzimmermann@suse.de" , "jessica.zhang@oss.qualcomm.com" , "sean@poorly.run" , "marijn.suijten@somainline.org" , "mcanal@igalia.com" , "dave.stevenson@raspberrypi.com" , "tomi.valkeinen+renesas@ideasonboard.com" , "kieran.bingham+renesas@ideasonboard.com" , "louis.chauvet@bootlin.com" Subject: Re: [RFC PATCH 1/8] drm: writeback: Refactor drm_writeback_connector structure Message-ID: <20250826-skinny-dancing-otter-de9be4@houat> References: <20250811092707.3986802-2-suraj.kandpal@intel.com> <20250811094429.GE21313@pendragon.ideasonboard.com> <20250811111546.GA30760@pendragon.ideasonboard.com> <2ah3pau7p7brgw7huoxznvej3djct76vgfwtc72n6uub7sjojd@zzaebjdcpdwf> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha384; protocol="application/pgp-signature"; boundary="h5fbt5za66ojtx6g" Content-Disposition: inline In-Reply-To: --h5fbt5za66ojtx6g Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [RFC PATCH 1/8] drm: writeback: Refactor drm_writeback_connector structure MIME-Version: 1.0 On Mon, Aug 25, 2025 at 06:26:48AM +0000, Kandpal, Suraj wrote: > > Subject: Re: [RFC PATCH 1/8] drm: writeback: Refactor > > drm_writeback_connector structure > >=20 > > Hi, > >=20 > > On Sat, Aug 16, 2025 at 01:20:53AM +0300, Dmitry Baryshkov wrote: > > > On Thu, Aug 14, 2025 at 05:13:54PM +0100, liviu.dudau@arm.com wrote: > > > > Hi, > > > > > > > > On Wed, Aug 13, 2025 at 10:04:22AM +0000, Kandpal, Suraj wrote: > > > > > > > > }; > > > > > > > > > > > > > > I still don't like that. This really doesn't belong here. If > > > > > > > anything, the drm_connector for writeback belongs to drm_crtc. > > > > > > > > > > > > Why? We already have generic HDMI field inside drm_connector. I > > > > > > am really hoping to be able to land DP parts next to it. In > > > > > > theory we can have a DVI- specific entry there (e.g. with the > > subconnector type). > > > > > > The idea is not to limit how the drivers subclass those structu= res. > > > > > > > > > > > > I don't see a good case why WB should deviate from that design. > > > > > > > > > > > > > If the issue is that some drivers need a custom drm_connector > > > > > > > subclass, then I'd rather turn the connector field of > > > > > > > drm_writeback_connector into a pointer. > > > > > > > > > > > > Having a pointer requires additional ops in order to get > > > > > > drm_connector from WB code and vice versa. Having > > > > > > drm_connector_wb inside drm_connector saves us from those ops > > (which don't manifest for any other kind of structure). > > > > > > Nor will it take any more space since union will reuse space > > > > > > already taken up by HDMI part. > > > > > > > > > > > > > > > > > > > > > > > Seems like this thread has died. We need to get a conclusion on t= he > > design. > > > > > Laurent do you have any issue with the design given Dmitry's > > > > > explanation as to why this Design is good for drm_writeback_conne= ctor. > > > > > > > > I'm with Laurent here. The idea for drm_connector (and a lot of drm > > > > structures) are to be used as base "classes" for extended > > > > structures. I don't know why HDMI connector ended up inside > > > > drm_connector as not all connectors have HDMI functionality, but th= at's a > > cleanup for another day. > > > > > > Maybe Maxime can better comment on it, but I think it was made exactly > > > for the purpose of not limiting the driver's design. For example, a > > > lot of drivers subclass drm_connector via drm_bridge_connector. If > > > struct drm_connector_hdmi was a wrapper around struct drm_connector, > > > then it would have been impossible to use HDMI helpers for bridge > > > drivers, while current design freely allows any driver to utilize > > > corresponding library code. > >=20 > > That's exactly why we ended up like this. With that design, we wouldn't= have > > been able to "inherit" two connector "classes": bridge_connector is one, > > intel_connector another one. > >=20 > > See here for the rationale: > > https://lore.kernel.org/dri-devel/ZOTDKHxn2bOg+Xmg@phenom.ffwll.local/ > >=20 > > I don't think the "but we'll bloat drm_connector" makes sense either. > > There's already a *lot* of things that aren't useful to every connector= (fwnode, > > display_info, edid in general, scaling, vrr, etc.) > >=20 > > And it's not like we allocate more than a handful of them during a syst= em's life. >=20 > So Are we okay with the approach mentioned here with the changes that hav= e been proposed here like > Having drm_writeback_connector in union with drm_hdmi_connector I don't think we need a union here. It artificially creates the same issue: we can't have two types for a connector if we do so. > Also one more thing I would like to clarify here is how everyone would > like the patches patches where each patch changes both the drm core > and all related drivers (ensures buildability but then review is tough > for each driver). Or patches where we have initial drm core changes > and then each patch does the all changes in a driver in its own > respective patch. The latter should be preferred, but if you can't maintain bisectability that way, then it's the most important and you should fall back to the former. Maxime --h5fbt5za66ojtx6g Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJQEABMJAB0WIQTkHFbLp4ejekA/qfgnX84Zoj2+dgUCaK3XPQAKCRAnX84Zoj2+ dkGOAXsF9clyGa0v79Lvcn8LKsqqNonbB//uZEuQy7tvsCVTi+DhFkU8idQEhmiv 4/hwQBIBdjsjXoUxkxPssK1Cqn88KbP1KGjTWNATiM+3ovUf9J35gCUaNCEzp/9o nS7FRKYC =Lfn+ -----END PGP SIGNATURE----- --h5fbt5za66ojtx6g--