drm/bridge: Extend bridge API to disable connector creation

Most bridge drivers create a DRM connector to model the connector at the
output of the bridge. This model is historical and has worked pretty
well so far, but causes several issues:

- It prevents supporting more complex display pipelines where DRM
connector operations are split over multiple components. For instance a
pipeline with a bridge connected to the DDC signals to read EDID data,
and another one connected to the HPD signal to detect connection and
disconnection, will not be possible to support through this model.

- It requires every bridge driver to implement similar connector
handling code, resulting in code duplication.

- It assumes that a bridge will either be wired to a connector or to
another bridge, but doesn't support bridges that can be used in both
positions very well (although there is some ad-hoc support for this in
the analogix_dp bridge driver).

In order to solve these issues, ownership of the connector should be
moved to the display controller driver (where it can be implemented
using helpers provided by the core).

Extend the bridge API to allow disabling connector creation in bridge
drivers as a first step towards the new model. The new flags argument to
the bridge .attach() operation allows instructing the bridge driver to
skip creating a connector. Unconditionally set the new flags argument to
0 for now to keep the existing behaviour, and modify all existing bridge
drivers to return an error when connector creation is not requested as
they don't support this feature yet.

The change is based on the following semantic patch, with manual review
and edits.

@ rule1 @
identifier funcs;
identifier fn;
@@
 struct drm_bridge_funcs funcs = {
 	...,
 	.attach = fn
 };

@ depends on rule1 @
identifier rule1.fn;
identifier bridge;
statement S, S1;
@@
 int fn(
 	struct drm_bridge *bridge
+	, enum drm_bridge_attach_flags flags
 )
 {
 	... when != S
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	S1
 	...
 }

@ depends on rule1 @
identifier rule1.fn;
identifier bridge, flags;
expression E1, E2, E3;
@@
 int fn(
 	struct drm_bridge *bridge,
 	enum drm_bridge_attach_flags flags
 ) {
 <...
 drm_bridge_attach(E1, E2, E3
+	, flags
 )
 ...>
 }

@@
expression E1, E2, E3;
@@
 drm_bridge_attach(E1, E2, E3
+	, 0
 )
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Tested-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200226112514.12455-10-laurent.pinchart@ideasonboard.com

drivers/gpu/drm/arc/arcpgu_hdmi.c

@@ -40,7 +40,7 @@ int arcpgu_drm_hdmi_init(struct drm_device *drm, struct device_node *np)
 		return ret;
 
 	/* Link drm_bridge to encoder */
-	ret = drm_bridge_attach(encoder, bridge, NULL);
+	ret = drm_bridge_attach(encoder, bridge, NULL, 0);
 	if (ret)
 		drm_encoder_cleanup(encoder);
 

drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c

@@ -114,7 +114,7 @@ static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
 	}
 
 	if (bridge) {
-		ret = drm_bridge_attach(&output->encoder, bridge, NULL);
+		ret = drm_bridge_attach(&output->encoder, bridge, NULL, 0);
 		if (!ret)
 			return 0;
 

drivers/gpu/drm/bridge/adv7511/adv7511_drv.c

@@ -847,11 +847,17 @@ static void adv7511_bridge_mode_set(struct drm_bridge *bridge,
 	adv7511_mode_set(adv, mode, adj_mode);
 }
 
-static int adv7511_bridge_attach(struct drm_bridge *bridge)
+static int adv7511_bridge_attach(struct drm_bridge *bridge,
+				 enum drm_bridge_attach_flags flags)
 {
 	struct adv7511 *adv = bridge_to_adv7511(bridge);
 	int ret;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	if (!bridge->encoder) {
 		DRM_ERROR("Parent encoder object not found");
 		return -ENODEV;

drivers/gpu/drm/bridge/analogix/analogix-anx6345.c

@@ -520,11 +520,17 @@ static const struct drm_connector_funcs anx6345_connector_funcs = {
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 };
 
-static int anx6345_bridge_attach(struct drm_bridge *bridge)
+static int anx6345_bridge_attach(struct drm_bridge *bridge,
+				 enum drm_bridge_attach_flags flags)
 {
 	struct anx6345 *anx6345 = bridge_to_anx6345(bridge);
 	int err;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	if (!bridge->encoder) {
 		DRM_ERROR("Parent encoder object not found");
 		return -ENODEV;

drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c

@@ -886,11 +886,17 @@ static const struct drm_connector_funcs anx78xx_connector_funcs = {
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 };
 
-static int anx78xx_bridge_attach(struct drm_bridge *bridge)
+static int anx78xx_bridge_attach(struct drm_bridge *bridge,
+				 enum drm_bridge_attach_flags flags)
 {
 	struct anx78xx *anx78xx = bridge_to_anx78xx(bridge);
 	int err;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	if (!bridge->encoder) {
 		DRM_ERROR("Parent encoder object not found");
 		return -ENODEV;

drivers/gpu/drm/bridge/analogix/analogix_dp_core.c

@@ -1216,13 +1216,19 @@ static const struct drm_connector_funcs analogix_dp_connector_funcs = {
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 };
 
-static int analogix_dp_bridge_attach(struct drm_bridge *bridge)
+static int analogix_dp_bridge_attach(struct drm_bridge *bridge,
+				     enum drm_bridge_attach_flags flags)
 {
 	struct analogix_dp_device *dp = bridge->driver_private;
 	struct drm_encoder *encoder = dp->encoder;
 	struct drm_connector *connector = NULL;
 	int ret = 0;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	if (!bridge->encoder) {
 		DRM_ERROR("Parent encoder object not found");
 		return -ENODEV;
@@ -1598,7 +1604,7 @@ static int analogix_dp_create_bridge(struct drm_device *drm_dev,
 	bridge->driver_private = dp;
 	bridge->funcs = &analogix_dp_bridge_funcs;
 
-	ret = drm_bridge_attach(dp->encoder, bridge, NULL);
+	ret = drm_bridge_attach(dp->encoder, bridge, NULL, 0);
 	if (ret) {
 		DRM_ERROR("failed to attach drm bridge\n");
 		return -EINVAL;

drivers/gpu/drm/bridge/cdns-dsi.c

@@ -644,7 +644,8 @@ static int cdns_dsi_check_conf(struct cdns_dsi *dsi,
 	return 0;
 }
 
-static int cdns_dsi_bridge_attach(struct drm_bridge *bridge)
+static int cdns_dsi_bridge_attach(struct drm_bridge *bridge,
+				  enum drm_bridge_attach_flags flags)
 {
 	struct cdns_dsi_input *input = bridge_to_cdns_dsi_input(bridge);
 	struct cdns_dsi *dsi = input_to_dsi(input);
@@ -656,7 +657,8 @@ static int cdns_dsi_bridge_attach(struct drm_bridge *bridge)
 		return -ENOTSUPP;
 	}
 
-	return drm_bridge_attach(bridge->encoder, output->bridge, bridge);
+	return drm_bridge_attach(bridge->encoder, output->bridge, bridge,
+				 flags);
 }
 
 static enum drm_mode_status

drivers/gpu/drm/bridge/dumb-vga-dac.c

@@ -100,11 +100,17 @@ static const struct drm_connector_funcs dumb_vga_con_funcs = {
 	.atomic_destroy_state	= drm_atomic_helper_connector_destroy_state,
 };
 
-static int dumb_vga_attach(struct drm_bridge *bridge)
+static int dumb_vga_attach(struct drm_bridge *bridge,
+			   enum drm_bridge_attach_flags flags)
 {
 	struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
 	int ret;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	if (!bridge->encoder) {
 		DRM_ERROR("Missing encoder\n");
 		return -ENODEV;

drivers/gpu/drm/bridge/lvds-codec.c

@@ -26,12 +26,13 @@ static inline struct lvds_codec *to_lvds_codec(struct drm_bridge *bridge)
 	return container_of(bridge, struct lvds_codec, bridge);
 }
 
-static int lvds_codec_attach(struct drm_bridge *bridge)
+static int lvds_codec_attach(struct drm_bridge *bridge,
+			     enum drm_bridge_attach_flags flags)
 {
 	struct lvds_codec *lvds_codec = to_lvds_codec(bridge);
 
 	return drm_bridge_attach(bridge->encoder, lvds_codec->panel_bridge,
-				 bridge);
+				 bridge, flags);
 }
 
 static void lvds_codec_enable(struct drm_bridge *bridge)

drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c

@@ -206,13 +206,19 @@ static irqreturn_t ge_b850v3_lvds_irq_handler(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-static int ge_b850v3_lvds_attach(struct drm_bridge *bridge)
+static int ge_b850v3_lvds_attach(struct drm_bridge *bridge,
+				 enum drm_bridge_attach_flags flags)
 {
 	struct drm_connector *connector = &ge_b850v3_lvds_ptr->connector;
 	struct i2c_client *stdp4028_i2c
 			= ge_b850v3_lvds_ptr->stdp4028_i2c;
 	int ret;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	if (!bridge->encoder) {
 		DRM_ERROR("Parent encoder object not found");
 		return -ENODEV;

drivers/gpu/drm/bridge/nxp-ptn3460.c

@@ -236,11 +236,17 @@ static const struct drm_connector_funcs ptn3460_connector_funcs = {
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 };
 
-static int ptn3460_bridge_attach(struct drm_bridge *bridge)
+static int ptn3460_bridge_attach(struct drm_bridge *bridge,
+				 enum drm_bridge_attach_flags flags)
 {
 	struct ptn3460_bridge *ptn_bridge = bridge_to_ptn3460(bridge);
 	int ret;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	if (!bridge->encoder) {
 		DRM_ERROR("Parent encoder object not found");
 		return -ENODEV;

drivers/gpu/drm/bridge/panel.c

@@ -53,12 +53,18 @@ static const struct drm_connector_funcs panel_bridge_connector_funcs = {
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 };
 
-static int panel_bridge_attach(struct drm_bridge *bridge)
+static int panel_bridge_attach(struct drm_bridge *bridge,
+			       enum drm_bridge_attach_flags flags)
 {
 	struct panel_bridge *panel_bridge = drm_bridge_to_panel_bridge(bridge);
 	struct drm_connector *connector = &panel_bridge->connector;
 	int ret;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	if (!bridge->encoder) {
 		DRM_ERROR("Missing encoder\n");
 		return -ENODEV;

drivers/gpu/drm/bridge/parade-ps8622.c

@@ -476,11 +476,17 @@ static const struct drm_connector_funcs ps8622_connector_funcs = {
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 };
 
-static int ps8622_attach(struct drm_bridge *bridge)
+static int ps8622_attach(struct drm_bridge *bridge,
+			 enum drm_bridge_attach_flags flags)
 {
 	struct ps8622_bridge *ps8622 = bridge_to_ps8622(bridge);
 	int ret;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	if (!bridge->encoder) {
 		DRM_ERROR("Parent encoder object not found");
 		return -ENODEV;

drivers/gpu/drm/bridge/parade-ps8640.c

@@ -187,7 +187,8 @@ static void ps8640_post_disable(struct drm_bridge *bridge)
 		DRM_ERROR("cannot disable regulators %d\n", ret);
 }
 
-static int ps8640_bridge_attach(struct drm_bridge *bridge)
+static int ps8640_bridge_attach(struct drm_bridge *bridge,
+				enum drm_bridge_attach_flags flags)
 {
 	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
 	struct device *dev = &ps_bridge->page[0]->dev;
@@ -234,7 +235,7 @@ static int ps8640_bridge_attach(struct drm_bridge *bridge)
 
 	/* Attach the panel-bridge to the dsi bridge */
 	return drm_bridge_attach(bridge->encoder, ps_bridge->panel_bridge,
-				 &ps_bridge->bridge);
+				 &ps_bridge->bridge, flags);
 
 err_dsi_attach:
 	mipi_dsi_device_unregister(dsi);

drivers/gpu/drm/bridge/sii902x.c

@@ -399,12 +399,18 @@ static void sii902x_bridge_mode_set(struct drm_bridge *bridge,
 	mutex_unlock(&sii902x->mutex);
 }
 
-static int sii902x_bridge_attach(struct drm_bridge *bridge)
+static int sii902x_bridge_attach(struct drm_bridge *bridge,
+				 enum drm_bridge_attach_flags flags)
 {
 	struct sii902x *sii902x = bridge_to_sii902x(bridge);
 	struct drm_device *drm = bridge->dev;
 	int ret;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	drm_connector_helper_add(&sii902x->connector,
 				 &sii902x_connector_helper_funcs);
 

drivers/gpu/drm/bridge/sil-sii8620.c

@@ -2202,7 +2202,8 @@ static inline struct sii8620 *bridge_to_sii8620(struct drm_bridge *bridge)
 	return container_of(bridge, struct sii8620, bridge);
 }
 
-static int sii8620_attach(struct drm_bridge *bridge)
+static int sii8620_attach(struct drm_bridge *bridge,
+			  enum drm_bridge_attach_flags flags)
 {
 	struct sii8620 *ctx = bridge_to_sii8620(bridge);
 

drivers/gpu/drm/bridge/synopsys/dw-hdmi.c

@@ -2371,7 +2371,8 @@ static const struct drm_connector_helper_funcs dw_hdmi_connector_helper_funcs =
 	.atomic_check = dw_hdmi_connector_atomic_check,
 };
 
-static int dw_hdmi_bridge_attach(struct drm_bridge *bridge)
+static int dw_hdmi_bridge_attach(struct drm_bridge *bridge,
+				 enum drm_bridge_attach_flags flags)
 {
 	struct dw_hdmi *hdmi = bridge->driver_private;
 	struct drm_encoder *encoder = bridge->encoder;
@@ -2379,6 +2380,11 @@ static int dw_hdmi_bridge_attach(struct drm_bridge *bridge)
 	struct cec_connector_info conn_info;
 	struct cec_notifier *notifier;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	connector->interlace_allowed = 1;
 	connector->polled = DRM_CONNECTOR_POLL_HPD;
 
@@ -3076,7 +3082,7 @@ struct dw_hdmi *dw_hdmi_bind(struct platform_device *pdev,
 	if (IS_ERR(hdmi))
 		return hdmi;
 
-	ret = drm_bridge_attach(encoder, &hdmi->bridge, NULL);
+	ret = drm_bridge_attach(encoder, &hdmi->bridge, NULL, 0);
 	if (ret) {
 		dw_hdmi_remove(hdmi);
 		DRM_ERROR("Failed to initialize bridge with drm\n");

drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c

@@ -936,7 +936,8 @@ dw_mipi_dsi_bridge_mode_valid(struct drm_bridge *bridge,
 	return mode_status;
 }
 
-static int dw_mipi_dsi_bridge_attach(struct drm_bridge *bridge)
+static int dw_mipi_dsi_bridge_attach(struct drm_bridge *bridge,
+				     enum drm_bridge_attach_flags flags)
 {
 	struct dw_mipi_dsi *dsi = bridge_to_dsi(bridge);
 
@@ -949,7 +950,8 @@ static int dw_mipi_dsi_bridge_attach(struct drm_bridge *bridge)
 	bridge->encoder->encoder_type = DRM_MODE_ENCODER_DSI;
 
 	/* Attach the panel-bridge to the dsi bridge */
-	return drm_bridge_attach(bridge->encoder, dsi->panel_bridge, bridge);
+	return drm_bridge_attach(bridge->encoder, dsi->panel_bridge, bridge,
+				 flags);
 }
 
 static const struct drm_bridge_funcs dw_mipi_dsi_bridge_funcs = {
@@ -1120,7 +1122,7 @@ int dw_mipi_dsi_bind(struct dw_mipi_dsi *dsi, struct drm_encoder *encoder)
 {
 	int ret;
 
-	ret = drm_bridge_attach(encoder, &dsi->bridge, NULL);
+	ret = drm_bridge_attach(encoder, &dsi->bridge, NULL, 0);
 	if (ret) {
 		DRM_ERROR("Failed to initialize bridge with drm\n");
 		return ret;

drivers/gpu/drm/bridge/tc358764.c

@@ -349,12 +349,18 @@ static void tc358764_enable(struct drm_bridge *bridge)
 		dev_err(ctx->dev, "error enabling panel (%d)\n", ret);
 }
 
-static int tc358764_attach(struct drm_bridge *bridge)
+static int tc358764_attach(struct drm_bridge *bridge,
+			   enum drm_bridge_attach_flags flags)
 {
 	struct tc358764 *ctx = bridge_to_tc358764(bridge);
 	struct drm_device *drm = bridge->dev;
 	int ret;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	ctx->connector.polled = DRM_CONNECTOR_POLL_HPD;
 	ret = drm_connector_init(drm, &ctx->connector,
 				 &tc358764_connector_funcs,

drivers/gpu/drm/bridge/tc358767.c

@@ -31,6 +31,7 @@
 #include <drm/drm_edid.h>
 #include <drm/drm_of.h>
 #include <drm/drm_panel.h>
+#include <drm/drm_print.h>
 #include <drm/drm_probe_helper.h>
 
 /* Registers */
@@ -1403,13 +1404,19 @@ static const struct drm_connector_funcs tc_connector_funcs = {
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 };
 
-static int tc_bridge_attach(struct drm_bridge *bridge)
+static int tc_bridge_attach(struct drm_bridge *bridge,
+			    enum drm_bridge_attach_flags flags)
 {
 	u32 bus_format = MEDIA_BUS_FMT_RGB888_1X24;
 	struct tc_data *tc = bridge_to_tc(bridge);
 	struct drm_device *drm = bridge->dev;
 	int ret;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	/* Create DP/eDP connector */
 	drm_connector_helper_add(&tc->connector, &tc_connector_helper_funcs);
 	ret = drm_connector_init(drm, &tc->connector, &tc_connector_funcs,

drivers/gpu/drm/bridge/tc358768.c

@@ -511,7 +511,8 @@ static const struct mipi_dsi_host_ops tc358768_dsi_host_ops = {
 	.transfer = tc358768_dsi_host_transfer,
 };
 
-static int tc358768_bridge_attach(struct drm_bridge *bridge)
+static int tc358768_bridge_attach(struct drm_bridge *bridge,
+				  enum drm_bridge_attach_flags flags)
 {
 	struct tc358768_priv *priv = bridge_to_tc358768(bridge);
 
@@ -520,7 +521,8 @@ static int tc358768_bridge_attach(struct drm_bridge *bridge)
 		return -ENOTSUPP;
 	}
 
-	return drm_bridge_attach(bridge->encoder, priv->output.bridge, bridge);
+	return drm_bridge_attach(bridge->encoder, priv->output.bridge, bridge,
+				 flags);
 }
 
 static enum drm_mode_status

drivers/gpu/drm/bridge/thc63lvd1024.c

@@ -42,11 +42,12 @@ static inline struct thc63_dev *to_thc63(struct drm_bridge *bridge)
 	return container_of(bridge, struct thc63_dev, bridge);
 }
 
-static int thc63_attach(struct drm_bridge *bridge)
+static int thc63_attach(struct drm_bridge *bridge,
+			enum drm_bridge_attach_flags flags)
 {
 	struct thc63_dev *thc63 = to_thc63(bridge);
 
-	return drm_bridge_attach(bridge->encoder, thc63->next, bridge);
+	return drm_bridge_attach(bridge->encoder, thc63->next, bridge, flags);
 }
 
 static enum drm_mode_status thc63_mode_valid(struct drm_bridge *bridge,

drivers/gpu/drm/bridge/ti-sn65dsi86.c

@@ -266,7 +266,8 @@ static int ti_sn_bridge_parse_regulators(struct ti_sn_bridge *pdata)
 				       pdata->supplies);
 }
 
-static int ti_sn_bridge_attach(struct drm_bridge *bridge)
+static int ti_sn_bridge_attach(struct drm_bridge *bridge,
+			       enum drm_bridge_attach_flags flags)
 {
 	int ret, val;
 	struct ti_sn_bridge *pdata = bridge_to_ti_sn_bridge(bridge);
@@ -277,6 +278,11 @@ static int ti_sn_bridge_attach(struct drm_bridge *bridge)
 						   .node = NULL,
 						 };
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	ret = drm_connector_init(bridge->dev, &pdata->connector,
 				 &ti_sn_bridge_connector_funcs,
 				 DRM_MODE_CONNECTOR_eDP);

drivers/gpu/drm/bridge/ti-tfp410.c

@@ -118,11 +118,17 @@ static const struct drm_connector_funcs tfp410_con_funcs = {
 	.atomic_destroy_state	= drm_atomic_helper_connector_destroy_state,
 };
 
-static int tfp410_attach(struct drm_bridge *bridge)
+static int tfp410_attach(struct drm_bridge *bridge,
+			 enum drm_bridge_attach_flags flags)
 {
 	struct tfp410 *dvi = drm_bridge_to_tfp410(bridge);
 	int ret;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	if (!bridge->encoder) {
 		dev_err(dvi->dev, "Missing encoder\n");
 		return -ENODEV;

drivers/gpu/drm/drm_bridge.c

@@ -149,6 +149,7 @@ static const struct drm_private_state_funcs drm_bridge_priv_state_funcs = {
  * @encoder: DRM encoder
  * @bridge: bridge to attach
  * @previous: previous bridge in the chain (optional)
+ * @flags: DRM_BRIDGE_ATTACH_* flags
  *
  * Called by a kms driver to link the bridge to an encoder's chain. The previous
  * argument specifies the previous bridge in the chain. If NULL, the bridge is
@@ -166,7 +167,8 @@ static const struct drm_private_state_funcs drm_bridge_priv_state_funcs = {
  * Zero on success, error code on failure
  */
 int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
-		      struct drm_bridge *previous)
+		      struct drm_bridge *previous,
+		      enum drm_bridge_attach_flags flags)
 {
 	int ret;
 
@@ -188,7 +190,7 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
 		list_add(&bridge->chain_node, &encoder->bridge_chain);
 
 	if (bridge->funcs->attach) {
-		ret = bridge->funcs->attach(bridge);
+		ret = bridge->funcs->attach(bridge, flags);
 		if (ret < 0)
 			goto err_reset_bridge;
 	}
@@ -312,6 +314,20 @@ void drm_bridge_detach(struct drm_bridge *bridge)
  *   allows providing a single static const &drm_bridge_funcs instance in
  *   bridge drivers, improving security by storing function pointers in
  *   read-only memory.
+ *
+ *   In order to ease transition, bridge drivers may support both the old and
+ *   new models by making connector creation optional and implementing the
+ *   connected-related bridge operations. Connector creation is then controlled
+ *   by the flags argument to the drm_bridge_attach() function. Display drivers
+ *   that support the new model and create connectors themselves shall set the
+ *   %DRM_BRIDGE_ATTACH_NO_CONNECTOR flag, and bridge drivers shall then skip
+ *   connector creation. For intermediate bridges in the chain, the flag shall
+ *   be passed to the drm_bridge_attach() call for the downstream bridge.
+ *   Bridge drivers that implement the new model only shall return an error
+ *   from their &drm_bridge_funcs.attach handler when the
+ *   %DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is not set. New display drivers
+ *   should use the new model, and convert the bridge drivers they use if
+ *   needed, in order to gradually transition to the new model.
  */
 
 /**

drivers/gpu/drm/drm_simple_kms_helper.c

@@ -229,7 +229,7 @@ static const struct drm_plane_funcs drm_simple_kms_plane_funcs = {
 int drm_simple_display_pipe_attach_bridge(struct drm_simple_display_pipe *pipe,
 					  struct drm_bridge *bridge)
 {
-	return drm_bridge_attach(&pipe->encoder, bridge, NULL);
+	return drm_bridge_attach(&pipe->encoder, bridge, NULL, 0);
 }
 EXPORT_SYMBOL(drm_simple_display_pipe_attach_bridge);
 

drivers/gpu/drm/exynos/exynos_dp.c

@@ -106,7 +106,8 @@ static int exynos_dp_bridge_attach(struct analogix_dp_plat_data *plat_data,
 
 	/* Pre-empt DP connector creation if there's a bridge */
 	if (dp->ptn_bridge) {
-		ret = drm_bridge_attach(&dp->encoder, dp->ptn_bridge, bridge);
+		ret = drm_bridge_attach(&dp->encoder, dp->ptn_bridge, bridge,
+					0);
 		if (ret) {
 			DRM_DEV_ERROR(dp->dev,
 				      "Failed to attach bridge to drm\n");

drivers/gpu/drm/exynos/exynos_drm_dsi.c

@@ -1540,7 +1540,7 @@ static int exynos_dsi_host_attach(struct mipi_dsi_host *host,
 
 	out_bridge  = of_drm_find_bridge(device->dev.of_node);
 	if (out_bridge) {
-		drm_bridge_attach(encoder, out_bridge, NULL);
+		drm_bridge_attach(encoder, out_bridge, NULL, 0);
 		dsi->out_bridge = out_bridge;
 		list_splice_init(&encoder->bridge_chain, &dsi->bridge_chain);
 	} else {
@@ -1717,7 +1717,7 @@ static int exynos_dsi_bind(struct device *dev, struct device *master,
 	if (dsi->in_bridge_node) {
 		in_bridge = of_drm_find_bridge(dsi->in_bridge_node);
 		if (in_bridge)
-			drm_bridge_attach(encoder, in_bridge, NULL);
+			drm_bridge_attach(encoder, in_bridge, NULL, 0);
 	}
 
 	return mipi_dsi_host_register(&dsi->dsi_host);

drivers/gpu/drm/exynos/exynos_hdmi.c

@@ -960,7 +960,7 @@ static int hdmi_create_connector(struct drm_encoder *encoder)
 	drm_connector_attach_encoder(connector, encoder);
 
 	if (hdata->bridge) {
-		ret = drm_bridge_attach(encoder, hdata->bridge, NULL);
+		ret = drm_bridge_attach(encoder, hdata->bridge, NULL, 0);
 		if (ret)
 			DRM_DEV_ERROR(hdata->dev, "Failed to attach bridge\n");
 	}

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c

@@ -151,5 +151,5 @@ int fsl_dcu_create_outputs(struct fsl_dcu_drm_device *fsl_dev)
 		return fsl_dcu_attach_panel(fsl_dev, panel);
 	}
 
-	return drm_bridge_attach(&fsl_dev->encoder, bridge, NULL);
+	return drm_bridge_attach(&fsl_dev->encoder, bridge, NULL, 0);
 }

drivers/gpu/drm/hisilicon/kirin/dw_drm_dsi.c

@@ -777,7 +777,7 @@ static int dsi_bridge_init(struct drm_device *dev, struct dw_dsi *dsi)
 	int ret;
 
 	/* associate the bridge to dsi encoder */
-	ret = drm_bridge_attach(encoder, bridge, NULL);
+	ret = drm_bridge_attach(encoder, bridge, NULL, 0);
 	if (ret) {
 		DRM_ERROR("failed to attach external bridge\n");
 		return ret;

drivers/gpu/drm/i2c/tda998x_drv.c

@@ -1356,10 +1356,16 @@ static int tda998x_connector_init(struct tda998x_priv *priv,
 
 /* DRM bridge functions */
 
-static int tda998x_bridge_attach(struct drm_bridge *bridge)
+static int tda998x_bridge_attach(struct drm_bridge *bridge,
+				 enum drm_bridge_attach_flags flags)
 {
 	struct tda998x_priv *priv = bridge_to_tda998x_priv(bridge);
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	return tda998x_connector_init(priv, bridge->dev);
 }
 
@@ -2022,7 +2028,7 @@ static int tda998x_encoder_init(struct device *dev, struct drm_device *drm)
 	if (ret)
 		goto err_encoder;
 
-	ret = drm_bridge_attach(&priv->encoder, &priv->bridge, NULL);
+	ret = drm_bridge_attach(&priv->encoder, &priv->bridge, NULL, 0);
 	if (ret)
 		goto err_bridge;
 

drivers/gpu/drm/imx/imx-ldb.c

@@ -446,7 +446,7 @@ static int imx_ldb_register(struct drm_device *drm,
 
 	if (imx_ldb_ch->bridge) {
 		ret = drm_bridge_attach(&imx_ldb_ch->encoder,
-					imx_ldb_ch->bridge, NULL);
+					imx_ldb_ch->bridge, NULL, 0);
 		if (ret) {
 			DRM_ERROR("Failed to initialize bridge with drm\n");
 			return ret;

drivers/gpu/drm/imx/parallel-display.c

@@ -292,7 +292,7 @@ static int imx_pd_register(struct drm_device *drm,
 			 DRM_MODE_ENCODER_NONE, NULL);
 
 	imxpd->bridge.funcs = &imx_pd_bridge_funcs;
-	drm_bridge_attach(encoder, &imxpd->bridge, NULL);
+	drm_bridge_attach(encoder, &imxpd->bridge, NULL, 0);
 
 	if (!imxpd->next_bridge) {
 		drm_connector_helper_add(&imxpd->connector,
@@ -307,7 +307,7 @@ static int imx_pd_register(struct drm_device *drm,
 
 	if (imxpd->next_bridge) {
 		ret = drm_bridge_attach(encoder, imxpd->next_bridge,
-					&imxpd->bridge);
+					&imxpd->bridge, 0);
 		if (ret < 0) {
 			dev_err(imxpd->dev, "failed to attach bridge: %d\n",
 				ret);

drivers/gpu/drm/ingenic/ingenic-drm.c

@@ -737,7 +737,7 @@ static int ingenic_drm_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	ret = drm_bridge_attach(&priv->encoder, bridge, NULL);
+	ret = drm_bridge_attach(&priv->encoder, bridge, NULL, 0);
 	if (ret) {
 		dev_err(dev, "Unable to attach bridge");
 		return ret;

drivers/gpu/drm/mcde/mcde_dsi.c

@@ -986,7 +986,8 @@ static void mcde_dsi_bridge_disable(struct drm_bridge *bridge)
 	clk_disable_unprepare(d->lp_clk);
 }
 
-static int mcde_dsi_bridge_attach(struct drm_bridge *bridge)
+static int mcde_dsi_bridge_attach(struct drm_bridge *bridge,
+				  enum drm_bridge_attach_flags flags)
 {
 	struct mcde_dsi *d = bridge_to_mcde_dsi(bridge);
 	struct drm_device *drm = bridge->dev;
@@ -998,7 +999,7 @@ static int mcde_dsi_bridge_attach(struct drm_bridge *bridge)
 	}
 
 	/* Attach the DSI bridge to the output (panel etc) bridge */
-	ret = drm_bridge_attach(bridge->encoder, d->bridge_out, bridge);
+	ret = drm_bridge_attach(bridge->encoder, d->bridge_out, bridge, flags);
 	if (ret) {
 		dev_err(d->dev, "failed to attach the DSI bridge\n");
 		return ret;

drivers/gpu/drm/mediatek/mtk_dpi.c

@@ -607,7 +607,7 @@ static int mtk_dpi_bind(struct device *dev, struct device *master, void *data)
 	/* Currently DPI0 is fixed to be driven by OVL1 */
 	dpi->encoder.possible_crtcs = BIT(1);
 
-	ret = drm_bridge_attach(&dpi->encoder, dpi->bridge, NULL);
+	ret = drm_bridge_attach(&dpi->encoder, dpi->bridge, NULL, 0);
 	if (ret) {
 		dev_err(dev, "Failed to attach bridge: %d\n", ret);
 		goto err_cleanup;

drivers/gpu/drm/mediatek/mtk_dsi.c

@@ -904,7 +904,7 @@ static int mtk_dsi_create_conn_enc(struct drm_device *drm, struct mtk_dsi *dsi)
 
 	/* If there's a bridge, attach to it and let it create the connector */
 	if (dsi->bridge) {
-		ret = drm_bridge_attach(&dsi->encoder, dsi->bridge, NULL);
+		ret = drm_bridge_attach(&dsi->encoder, dsi->bridge, NULL, 0);
 		if (ret) {
 			DRM_ERROR("Failed to attach bridge to drm\n");
 			goto err_encoder_cleanup;

drivers/gpu/drm/mediatek/mtk_hdmi.c

@@ -1297,11 +1297,17 @@ static void mtk_hdmi_hpd_event(bool hpd, struct device *dev)
  * Bridge callbacks
  */
 
-static int mtk_hdmi_bridge_attach(struct drm_bridge *bridge)
+static int mtk_hdmi_bridge_attach(struct drm_bridge *bridge,
+				  enum drm_bridge_attach_flags flags)
 {
 	struct mtk_hdmi *hdmi = hdmi_ctx_from_bridge(bridge);
 	int ret;
 
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
+
 	ret = drm_connector_init_with_ddc(bridge->encoder->dev, &hdmi->conn,
 					  &mtk_hdmi_connector_funcs,
 					  DRM_MODE_CONNECTOR_HDMIA,
@@ -1326,7 +1332,7 @@ static int mtk_hdmi_bridge_attach(struct drm_bridge *bridge)
 
 	if (hdmi->next_bridge) {
 		ret = drm_bridge_attach(bridge->encoder, hdmi->next_bridge,
-					bridge);
+					bridge, flags);
 		if (ret) {
 			dev_err(hdmi->dev,
 				"Failed to attach external bridge: %d\n", ret);

drivers/gpu/drm/msm/dsi/dsi_manager.c

@@ -684,7 +684,7 @@ struct drm_bridge *msm_dsi_manager_bridge_init(u8 id)
 	bridge = &dsi_bridge->base;
 	bridge->funcs = &dsi_mgr_bridge_funcs;
 
-	ret = drm_bridge_attach(encoder, bridge, NULL);
+	ret = drm_bridge_attach(encoder, bridge, NULL, 0);
 	if (ret)
 		goto fail;
 
@@ -713,7 +713,7 @@ struct drm_connector *msm_dsi_manager_ext_bridge_init(u8 id)
 	encoder = msm_dsi->encoder;
 
 	/* link the internal dsi bridge to the external bridge */
-	drm_bridge_attach(encoder, ext_bridge, int_bridge);
+	drm_bridge_attach(encoder, ext_bridge, int_bridge, 0);
 
 	/*
 	 * we need the drm_connector created by the external bridge

drivers/gpu/drm/msm/edp/edp.c

@@ -178,7 +178,7 @@ int msm_edp_modeset_init(struct msm_edp *edp, struct drm_device *dev,
 		goto fail;
 	}
 
-	ret = drm_bridge_attach(encoder, edp->bridge, NULL);
+	ret = drm_bridge_attach(encoder, edp->bridge, NULL, 0);
 	if (ret)
 		goto fail;
 

drivers/gpu/drm/msm/edp/edp_bridge.c

@@ -97,7 +97,7 @@ struct drm_bridge *msm_edp_bridge_init(struct msm_edp *edp)
 	bridge = &edp_bridge->base;
 	bridge->funcs = &edp_bridge_funcs;
 
-	ret = drm_bridge_attach(edp->encoder, bridge, NULL);
+	ret = drm_bridge_attach(edp->encoder, bridge, NULL, 0);
 	if (ret)
 		goto fail;
 

drivers/gpu/drm/msm/hdmi/hdmi.c

@@ -327,7 +327,7 @@ int msm_hdmi_modeset_init(struct hdmi *hdmi,
 		goto fail;
 	}
 
-	ret = drm_bridge_attach(encoder, hdmi->bridge, NULL);
+	ret = drm_bridge_attach(encoder, hdmi->bridge, NULL, 0);
 	if (ret)
 		goto fail;
 

drivers/gpu/drm/msm/hdmi/hdmi_bridge.c

@@ -287,7 +287,7 @@ struct drm_bridge *msm_hdmi_bridge_init(struct hdmi *hdmi)
 	bridge = &hdmi_bridge->base;
 	bridge->funcs = &msm_hdmi_bridge_funcs;
 
-	ret = drm_bridge_attach(hdmi->encoder, bridge, NULL);
+	ret = drm_bridge_attach(hdmi->encoder, bridge, NULL, 0);
 	if (ret)
 		goto fail;
 

drivers/gpu/drm/omapdrm/omap_drv.c

@@ -297,7 +297,7 @@ static int omap_modeset_init(struct drm_device *dev)
 
 		if (pipe->output->bridge) {
 			ret = drm_bridge_attach(pipe->encoder,
-						pipe->output->bridge, NULL);
+						pipe->output->bridge, NULL, 0);
 			if (ret < 0)
 				return ret;
 		}

drivers/gpu/drm/rcar-du/rcar_du_encoder.c

@@ -121,7 +121,7 @@ int rcar_du_encoder_init(struct rcar_du_device *rcdu,
 	 * Attach the bridge to the encoder. The bridge will create the
 	 * connector.
 	 */
-	ret = drm_bridge_attach(encoder, bridge, NULL);
+	ret = drm_bridge_attach(encoder, bridge, NULL, 0);
 	if (ret) {
 		drm_encoder_cleanup(encoder);
 		return ret;

drivers/gpu/drm/rcar-du/rcar_lvds.c

@@ -23,6 +23,7 @@
 #include <drm/drm_bridge.h>
 #include <drm/drm_of.h>
 #include <drm/drm_panel.h>
+#include <drm/drm_print.h>
 #include <drm/drm_probe_helper.h>
 
 #include "rcar_lvds.h"
@@ -643,7 +644,8 @@ static bool rcar_lvds_mode_fixup(struct drm_bridge *bridge,
 	return true;
 }
 
-static int rcar_lvds_attach(struct drm_bridge *bridge)
+static int rcar_lvds_attach(struct drm_bridge *bridge,
+			    enum drm_bridge_attach_flags flags)
 {
 	struct rcar_lvds *lvds = bridge_to_rcar_lvds(bridge);
 	struct drm_connector *connector = &lvds->connector;
@@ -653,7 +655,12 @@ static int rcar_lvds_attach(struct drm_bridge *bridge)
 	/* If we have a next bridge just attach it. */
 	if (lvds->next_bridge)
 		return drm_bridge_attach(bridge->encoder, lvds->next_bridge,
-					 bridge);
+					 bridge, flags);
+
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+		DRM_ERROR("Fix bridge driver to make connector optional!");
+		return -EINVAL;
+	}
 
 	/* Otherwise if we have a panel, create a connector. */
 	if (!lvds->panel)

drivers/gpu/drm/rockchip/rockchip_lvds.c

@@ -646,7 +646,7 @@ static int rockchip_lvds_bind(struct device *dev, struct device *master,
 			goto err_free_connector;
 		}
 	} else {
-		ret = drm_bridge_attach(encoder, lvds->bridge, NULL);
+		ret = drm_bridge_attach(encoder, lvds->bridge, NULL, 0);
 		if (ret) {
 			DRM_DEV_ERROR(drm_dev->dev,
 				      "failed to attach bridge: %d\n", ret);

drivers/gpu/drm/rockchip/rockchip_rgb.c

@@ -144,7 +144,7 @@ struct rockchip_rgb *rockchip_rgb_init(struct device *dev,
 
 	rgb->bridge = bridge;
 
-	ret = drm_bridge_attach(encoder, rgb->bridge, NULL);
+	ret = drm_bridge_attach(encoder, rgb->bridge, NULL, 0);
 	if (ret) {
 		DRM_DEV_ERROR(drm_dev->dev,
 			      "failed to attach bridge: %d\n", ret);

drivers/gpu/drm/sti/sti_dvo.c

@@ -467,7 +467,7 @@ static int sti_dvo_bind(struct device *dev, struct device *master, void *data)
 	bridge->of_node = dvo->dev.of_node;
 	drm_bridge_add(bridge);
 
-	err = drm_bridge_attach(encoder, bridge, NULL);
+	err = drm_bridge_attach(encoder, bridge, NULL, 0);
 	if (err) {
 		DRM_ERROR("Failed to attach bridge\n");
 		return err;

drivers/gpu/drm/sti/sti_hda.c

@@ -701,7 +701,7 @@ static int sti_hda_bind(struct device *dev, struct device *master, void *data)
 
 	bridge->driver_private = hda;
 	bridge->funcs = &sti_hda_bridge_funcs;
-	drm_bridge_attach(encoder, bridge, NULL);
+	drm_bridge_attach(encoder, bridge, NULL, 0);
 
 	connector->encoder = encoder;
 

drivers/gpu/drm/sti/sti_hdmi.c

@@ -1281,7 +1281,7 @@ static int sti_hdmi_bind(struct device *dev, struct device *master, void *data)
 
 	bridge->driver_private = hdmi;
 	bridge->funcs = &sti_hdmi_bridge_funcs;
-	drm_bridge_attach(encoder, bridge, NULL);
+	drm_bridge_attach(encoder, bridge, NULL, 0);
 
 	connector->encoder = encoder;
 

drivers/gpu/drm/stm/ltdc.c

@@ -1109,7 +1109,7 @@ static int ltdc_encoder_init(struct drm_device *ddev, struct drm_bridge *bridge)
 
 	drm_encoder_helper_add(encoder, &ltdc_encoder_helper_funcs);
 
-	ret = drm_bridge_attach(encoder, bridge, NULL);
+	ret = drm_bridge_attach(encoder, bridge, NULL, 0);
 	if (ret) {
 		drm_encoder_cleanup(encoder);
 		return -EINVAL;

drivers/gpu/drm/sun4i/sun4i_lvds.c

@@ -156,7 +156,7 @@ int sun4i_lvds_init(struct drm_device *drm, struct sun4i_tcon *tcon)
 	}
 
 	if (bridge) {
-		ret = drm_bridge_attach(encoder, bridge, NULL);
+		ret = drm_bridge_attach(encoder, bridge, NULL, 0);
 		if (ret) {
 			dev_err(drm->dev, "Couldn't attach our bridge\n");
 			goto err_cleanup_connector;

drivers/gpu/drm/sun4i/sun4i_rgb.c

@@ -253,7 +253,7 @@ int sun4i_rgb_init(struct drm_device *drm, struct sun4i_tcon *tcon)
 	}
 
 	if (rgb->bridge) {
-		ret = drm_bridge_attach(encoder, rgb->bridge, NULL);
+		ret = drm_bridge_attach(encoder, rgb->bridge, NULL, 0);
 		if (ret) {
 			dev_err(drm->dev, "Couldn't attach our bridge\n");
 			goto err_cleanup_connector;

drivers/gpu/drm/tidss/tidss_kms.c

@@ -172,7 +172,7 @@ static int tidss_dispc_modeset_init(struct tidss_device *tidss)
 			return PTR_ERR(enc);
 		}
 
-		ret = drm_bridge_attach(enc, pipes[i].bridge, NULL);
+		ret = drm_bridge_attach(enc, pipes[i].bridge, NULL, 0);
 		if (ret) {
 			dev_err(tidss->dev, "bridge attach failed: %d\n", ret);
 			return ret;

drivers/gpu/drm/tilcdc/tilcdc_external.c

@@ -95,7 +95,7 @@ int tilcdc_attach_bridge(struct drm_device *ddev, struct drm_bridge *bridge)
 
 	priv->external_encoder->possible_crtcs = BIT(0);
 
-	ret = drm_bridge_attach(priv->external_encoder, bridge, NULL);
+	ret = drm_bridge_attach(priv->external_encoder, bridge, NULL, 0);
 	if (ret) {
 		dev_err(ddev->dev, "drm_bridge_attach() failed %d\n", ret);
 		return ret;

drivers/gpu/drm/vc4/vc4_dpi.c

@@ -252,7 +252,7 @@ static int vc4_dpi_init_bridge(struct vc4_dpi *dpi)
 		bridge = drm_panel_bridge_add_typed(panel,
 						    DRM_MODE_CONNECTOR_DPI);
 
-	return drm_bridge_attach(dpi->encoder, bridge, NULL);
+	return drm_bridge_attach(dpi->encoder, bridge, NULL, 0);
 }
 
 static int vc4_dpi_bind(struct device *dev, struct device *master, void *data)

drivers/gpu/drm/vc4/vc4_dsi.c

@@ -1619,7 +1619,7 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
 			 DRM_MODE_ENCODER_DSI, NULL);
 	drm_encoder_helper_add(dsi->encoder, &vc4_dsi_encoder_helper_funcs);
 
-	ret = drm_bridge_attach(dsi->encoder, dsi->bridge, NULL);
+	ret = drm_bridge_attach(dsi->encoder, dsi->bridge, NULL, 0);
 	if (ret) {
 		dev_err(dev, "bridge attach failed: %d\n", ret);
 		return ret;

include/drm/drm_bridge.h

@@ -39,6 +39,17 @@ struct drm_panel;
 struct edid;
 struct i2c_adapter;
 
+/**
+ * enum drm_bridge_attach_flags - Flags for &drm_bridge_funcs.attach
+ */
+enum drm_bridge_attach_flags {
+	/**
+	 * @DRM_BRIDGE_ATTACH_NO_CONNECTOR: When this flag is set the bridge
+	 * shall not create a drm_connector.
+	 */
+	DRM_BRIDGE_ATTACH_NO_CONNECTOR = BIT(0),
+};
+
 /**
  * struct drm_bridge_funcs - drm_bridge control functions
  */
@@ -47,7 +58,8 @@ struct drm_bridge_funcs {
 	 * @attach:
 	 *
 	 * This callback is invoked whenever our bridge is being attached to a
-	 * &drm_encoder.
+	 * &drm_encoder. The flags argument tunes the behaviour of the attach
+	 * operation (see DRM_BRIDGE_ATTACH_*).
 	 *
 	 * The @attach callback is optional.
 	 *
@@ -55,7 +67,8 @@ struct drm_bridge_funcs {
 	 *
 	 * Zero on success, error code on failure.
 	 */
-	int (*attach)(struct drm_bridge *bridge);
+	int (*attach)(struct drm_bridge *bridge,
+		      enum drm_bridge_attach_flags flags);
 
 	/**
 	 * @detach:
@@ -757,7 +770,8 @@ void drm_bridge_add(struct drm_bridge *bridge);
 void drm_bridge_remove(struct drm_bridge *bridge);
 struct drm_bridge *of_drm_find_bridge(struct device_node *np);
 int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
-		      struct drm_bridge *previous);
+		      struct drm_bridge *previous,
+		      enum drm_bridge_attach_flags flags);
 
 /**
  * drm_bridge_get_next_bridge() - Get the next bridge in the chain