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<1a8b1a34-89bd-436e-8b5c-64ea71e8f333@nxp.com> Date: Thu, 2 Apr 2026 12:55:32 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 10/10] drm/mxsfb/lcdif: use DRM_BRIDGE_ATTACH_NO_CONNECTOR and the bridge-connector To: Luca Ceresoli , Marek Vasut , Stefan Agner , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Rob Herring , Saravana Kannan Cc: Damon Ding , "Kory Maincent (TI.com)" , =?UTF-8?Q?Herv=C3=A9_Codina?= , Hui Pu , Ian Ray , Thomas Petazzoni , dri-devel@lists.freedesktop.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, Adam Ford , Alexander Stein , Christopher Obbard , Daniel Scally , Emanuele Ghidoli , Fabio Estevam , Francesco Dolcini , Frieder Schrempf , Gilles Talis , =?UTF-8?B?R29yYW4gUmHEkWVub3ZpxIc=?= , Heiko Schocher , Josua Mayer , Kieran Bingham , Marco Felsch , Martyn Welch , Oleksij Rempel , Peng Fan , Richard Hu , Shengjiu Wang , Stefan Eichenberger , Vitor Soares References: <20260330-drm-lcdif-dbanc-v2-0-c7f2af536a24@bootlin.com> <20260330-drm-lcdif-dbanc-v2-10-c7f2af536a24@bootlin.com> From: Liu Ying Content-Language: en-US In-Reply-To: <20260330-drm-lcdif-dbanc-v2-10-c7f2af536a24@bootlin.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SI2P153CA0025.APCP153.PROD.OUTLOOK.COM (2603:1096:4:190::12) To AM7PR04MB7046.eurprd04.prod.outlook.com (2603:10a6:20b:113::22) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: AM7PR04MB7046:EE_|AS8PR04MB8994:EE_ X-MS-Office365-Filtering-Correlation-Id: bee08a06-bd1e-4bd8-2035-08de9073e91b X-LD-Processed: 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09:25:51PM +0200, Luca Ceresoli wrote: > Convert this driver to DRM_BRIDGE_ATTACH_NO_CONNECTOR and to the > drm_bridge_connector framework which is the current DRM bridge best > practice. > > Tested-by: Martyn Welch > Tested-by: Alexander Stein # TQMa8MPxL/MBa8MPxL > Signed-off-by: Luca Ceresoli > > --- > > Changes in v2: > - Added missing select DRM_DISPLAY_HELPER in Kconfig > - Rebased on previous patch changes > --- > drivers/gpu/drm/mxsfb/Kconfig | 2 ++ > drivers/gpu/drm/mxsfb/lcdif_drv.c | 16 +++++++++++++++- > 2 files changed, 17 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/mxsfb/Kconfig b/drivers/gpu/drm/mxsfb/Kconfig > index 264e74f45554..31db7a824a93 100644 > --- a/drivers/gpu/drm/mxsfb/Kconfig > +++ b/drivers/gpu/drm/mxsfb/Kconfig > @@ -33,6 +33,8 @@ config DRM_IMX_LCDIF > select DRM_GEM_DMA_HELPER > select DRM_PANEL > select DRM_PANEL_BRIDGE > + select DRM_DISPLAY_HELPER > + select DRM_BRIDGE_CONNECTOR > help > Choose this option if you have an LCDIFv3 LCD controller. > Those devices are found in various i.MX SoC (i.MX8MP, > diff --git a/drivers/gpu/drm/mxsfb/lcdif_drv.c b/drivers/gpu/drm/mxsfb/lcdif_drv.c > index c8ba8f9b1da8..7f07ae24e0dc 100644 > --- a/drivers/gpu/drm/mxsfb/lcdif_drv.c > +++ b/drivers/gpu/drm/mxsfb/lcdif_drv.c > @@ -18,6 +18,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -57,6 +58,7 @@ static int lcdif_attach_bridge(struct lcdif_drm_private *lcdif) > struct of_endpoint of_ep; > struct drm_bridge *bridge; > struct drm_encoder *encoder; > + struct drm_connector *connector; > int ret; > > if (!of_device_is_available(remote)) > @@ -86,11 +88,23 @@ static int lcdif_attach_bridge(struct lcdif_drm_private *lcdif) > "Failed to initialize encoder for endpoint%u\n", > of_ep.id); > > - ret = drm_bridge_attach(encoder, bridge, NULL, 0); > + ret = drm_bridge_attach(encoder, bridge, NULL, DRM_BRIDGE_ATTACH_NO_CONNECTOR); It seems that only analogix-anx6345.c, analogix-anx78xx.c and analogix_dp_core.c don't allow DRM_BRIDGE_ATTACH_NO_CONNECTOR, since they error out when attaching the bridge with the flag: if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) { DRM_ERROR("Fix bridge driver to make connector optional!"); return -EINVAL; } Looks like i.MX8MP platforms don't use these drivers. But, are we completely safe here by adding the flag? You also mentioned "pitfalls" in commit mesg, which makes me a bit more worried. Sorry for not bringing this up in v1. > if (ret) > return dev_err_probe(dev, ret, > "Failed to attach bridge for endpoint%u\n", > of_ep.id); > + > + connector = drm_bridge_connector_init(lcdif->drm, encoder); Also, kernel doc of drm_bridge_connector.c says: * To make use of this helper, all bridges in the chain shall report bridge * operation flags (&drm_bridge->ops) and bridge output type * (&drm_bridge->type), as well as the DRM_BRIDGE_ATTACH_NO_CONNECTOR attach * flag (none of the bridges shall create a DRM connector directly). Are you sure that we are safe to use this helper? > + if (IS_ERR(connector)) > + return dev_err_probe(dev, PTR_ERR(connector), > + "Failed to init bridge_connector for endpoint%u\n", > + of_ep.id); > + > + ret = drm_connector_attach_encoder(connector, encoder); > + if (ret) > + return dev_err_probe(dev, ret, > + "Failed to attach connector for endpoint%u\n", > + of_ep.id); > } > > return 0; > -- Regards, Liu Ying