From: Luca Ceresoli <luca.ceresoli@bootlin•com>
To: Maarten Lankhorst <maarten.lankhorst@linux•intel.com>,
Maxime Ripard <mripard@kernel•org>,
Thomas Zimmermann <tzimmermann@suse•de>,
David Airlie <airlied@gmail•com>,
Simona Vetter <simona@ffwll•ch>,
Andrzej Hajda <andrzej.hajda@intel•com>,
Neil Armstrong <neil.armstrong@linaro•org>,
Robert Foss <rfoss@kernel•org>,
Laurent Pinchart <Laurent.pinchart@ideasonboard•com>,
Jonas Karlman <jonas@kwiboo•se>,
Jernej Skrabec <jernej.skrabec@gmail•com>,
Inki Dae <inki.dae@samsung•com>,
Jagan Teki <jagan@amarulasolutions•com>,
Marek Szyprowski <m.szyprowski@samsung•com>,
Marek Vasut <marex@denx•de>, Stefan Agner <stefan@agner•ch>,
Frank Li <Frank.Li@nxp•com>,
Sascha Hauer <s.hauer@pengutronix•de>,
Pengutronix Kernel Team <kernel@pengutronix•de>,
Fabio Estevam <festevam@gmail•com>
Cc: Hui Pu <Hui.Pu@gehealthcare•com>,
Ian Ray <ian.ray@gehealthcare•com>,
Thomas Petazzoni <thomas.petazzoni@bootlin•com>,
dri-devel@lists•freedesktop.org, linux-kernel@vger•kernel.org,
imx@lists•linux.dev, linux-arm-kernel@lists•infradead.org,
Luca Ceresoli <luca.ceresoli@bootlin•com>
Subject: [PATCH 30/37] drm/bridge: add drm_bridge_is_tail() to know whether a bridge completes the pipeline
Date: Tue, 19 May 2026 12:37:47 +0200 [thread overview]
Message-ID: <20260519-drm-bridge-hotplug-v1-30-45e2bdb3dfb4@bootlin.com> (raw)
In-Reply-To: <20260519-drm-bridge-hotplug-v1-0-45e2bdb3dfb4@bootlin.com>
For bridge hotplug we need to successfully probe a card with an incomplete
bridge chain, i.e. a chain whose last bridge currently in bridge_chain
needs a next_bridge to work. Such a card would have no connector, and be
able to add one as soon as the followong bridges are added up to the tail
bridge (e.g. a panel_bridge or a connector_bridge).
Currently common DRM code is unable to tell whether the last bridge
currently in the chain is the tail bridge (= the pipeline is complete) or
not.
Add drm_bridge_is_tail(), and a .is_tail func for it to rely on, so common
code can know whether a bridge is a tail bridge or needs a next_bridge.
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin•com>
---
drivers/gpu/drm/drm_bridge.c | 28 ++++++++++++++++++++++++++++
include/drm/drm_bridge.h | 19 +++++++++++++++++++
2 files changed, 47 insertions(+)
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index c62d17e84d4f..2b539c9749a6 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -646,6 +646,34 @@ void drm_bridge_detach(struct drm_bridge *bridge)
drm_bridge_put(bridge);
}
+/**
+ * drm_bridge_is_tail - check whether the bridge is the last required to
+ * have a full pipeline
+ * @bridge: the bridge to check
+ *
+ * Tell whether this is a tail bridge, i.e. a bridge that does not need a
+ * next bridge to work. E.g. a panel_bridge is final, a DSI-to-LVDS bridge
+ * is not.
+ *
+ * In case of hotplug the last bridge currently in the chain (as in
+ * drm_bridge_chain_get_last_bridge()) might not be final, and be waiting
+ * for a pipeline tail to be connected.
+ *
+ * Return: true if this bridge does not need a next bridge to work, false
+ * otherwise
+ */
+bool drm_bridge_is_tail(struct drm_bridge *bridge)
+{
+ if (!(bridge->ops & DRM_BRIDGE_OP_IS_TAIL)) {
+ drm_warn_once(bridge->dev, "is_tail func not implemented by bridge %ps!",
+ bridge->funcs);
+ return false;
+ }
+
+ return bridge->funcs->is_tail(bridge);
+}
+EXPORT_SYMBOL(drm_bridge_is_tail);
+
/**
* DOC: bridge operations
*
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 4ba3a5deef9a..d783a6fb93a0 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -78,6 +78,19 @@ struct drm_bridge_funcs {
int (*attach)(struct drm_bridge *bridge, struct drm_encoder *encoder,
enum drm_bridge_attach_flags flags);
+ /**
+ * @is_tail:
+ *
+ * Returns true if this is a tail bridge, i.e. it does not need a
+ * next bridge to work. E.g. a panel_bridge is a tail bridge, a
+ * DSI-to-LVDS bridge is not a tail bridge (no matter whether the
+ * next bridge is present or not).
+ *
+ * The @is_tail callback is optional but it is required if the
+ * bridge is part of a pipeline with hot-pluggable components.
+ */
+ bool (*is_tail)(struct drm_bridge *bridge);
+
/**
* @destroy:
*
@@ -1092,6 +1105,11 @@ enum drm_bridge_ops {
* &drm_bridge_funcs->hdmi_clear_spd_infoframe callbacks.
*/
DRM_BRIDGE_OP_HDMI_SPD_INFOFRAME = BIT(10),
+ /**
+ * @DRM_BRIDGE_OP_IS_TAIL: The bridge implements the
+ * &drm_bridge_funcs->is_tail callback.
+ */
+ DRM_BRIDGE_OP_IS_TAIL = BIT(11),
};
/**
@@ -1323,6 +1341,7 @@ void drm_bridge_remove(struct drm_bridge *bridge);
int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
struct drm_bridge *previous,
enum drm_bridge_attach_flags flags);
+bool drm_bridge_is_tail(struct drm_bridge *bridge);
#ifdef CONFIG_OF
struct drm_bridge *of_drm_find_and_get_bridge(struct device_node *np);
--
2.54.0
next prev parent reply other threads:[~2026-05-19 10:40 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-19 10:37 [PATCH 00/37] drm bridge hotplug Luca Ceresoli
2026-05-19 10:37 ` [PATCH 01/37] drm/connector: split drmm_connector_hdmi_init() in 3 parts Luca Ceresoli
2026-05-19 10:37 ` [PATCH 02/37] drm/connector: add drm_connector_hdmi_dynamic_init() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 03/37] drm/display: bridge-connector: rename variable for consistency Luca Ceresoli
2026-05-19 10:37 ` [PATCH 04/37] drm/display: bridge-connector: store the drm_device pointer Luca Ceresoli
2026-05-19 10:37 ` [PATCH 05/37] drm/display: bridge-connector: split code creating the connector to a subfunction Luca Ceresoli
2026-05-19 10:37 ` [PATCH 06/37] drm/display: bridge-connector: use a drm_bridge_connector internally, not a drm_connector Luca Ceresoli
2026-05-19 10:37 ` [PATCH 07/37] drm/display: bridge-connector: extract drm_bridge_connector_get_bridges() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 08/37] drm/display: bridge-connector: return int from drm_bridge_connector_get_bridges() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 09/37] drm/display: bridge-connector: extract drm_bridge_connector_init_hdmi_audio_cec() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 10/37] drm/display: bridge-connector: return int from drm_bridge_connector_init_hdmi_audio_cec() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 11/37] drm/display: bridge-connector: return int from drm_bridge_connector_add_connector() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 12/37] drm/display: bridge-connector: hoist error management to common code Luca Ceresoli
2026-05-19 10:37 ` [PATCH 13/37] drm/display: bridge-connector: move drm_bridge_connector_put_bridges() definition eariler Luca Ceresoli
2026-05-19 10:37 ` [PATCH 14/37] drm/display: bridge-connector: add non-drmm variant of drm_bridge_connector_put_bridges() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 15/37] drm/display: bridge-connector: allocate the connector dynamically Luca Ceresoli
2026-05-19 10:37 ` [PATCH 16/37] drm/display: bridge-connector: move per-connector fields to the dynamic connector Luca Ceresoli
2026-05-19 10:37 ` [PATCH 17/37] drm/display: bridge-connector: protect dynconn creation and destruction with a mutex Luca Ceresoli
2026-05-19 10:37 ` [PATCH 18/37] drm/bridge: samsung-dsim: remove the panel_bridge on host_detach Luca Ceresoli
2026-05-19 10:37 ` [PATCH 19/37] drm/bridge: samsung-dsim: move drm_bridge_add() call to probe Luca Ceresoli
2026-05-19 10:37 ` [PATCH 20/37] drm/bridge: samsung-dsim: attach: return -EPROBE_DEFER is next bridge not yet available Luca Ceresoli
2026-05-19 10:37 ` [PATCH 21/37] drm/bridge: initialize chain_node list head on allocation Luca Ceresoli
2026-05-19 10:37 ` [PATCH 22/37] drm/bridge: initialize chain_node list head on detach and attach errors Luca Ceresoli
2026-05-19 10:37 ` [PATCH 23/37] drm/encoder: add drm_encoder_cleanup_from() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 24/37] drm/atomic: move drm_atomic_helper_disable_all() and drm_atomic_helper_shutdown() from drm_atomic_helper to drm_atomic Luca Ceresoli
2026-05-19 10:37 ` [PATCH 25/37] drm/bridge: shutdown and cleanup on bridge unplug Luca Ceresoli
2026-05-19 10:37 ` [PATCH 26/37] drm: event-notifier: add mechanism to notify about hotplug events Luca Ceresoli
2026-05-19 10:37 ` [PATCH 27/37] drm/bridge: notify about detached bridges Luca Ceresoli
2026-05-19 10:37 ` [PATCH 28/37] drm/mipi-dsi: turn DRM_MIPI_DSI into a tristate Luca Ceresoli
2026-05-19 10:37 ` [PATCH 29/37] drm/mipi-dsi: notify about DSI attach Luca Ceresoli
2026-05-19 10:37 ` Luca Ceresoli [this message]
2026-05-19 10:37 ` [PATCH 31/37] drm/bridge: panel: implement .is_tail Luca Ceresoli
2026-05-19 15:12 ` Neil Armstrong
2026-05-19 10:37 ` [PATCH 32/37] drm/bridge: display-connector: " Luca Ceresoli
2026-05-19 10:37 ` [PATCH 33/37] drm/bridge: samsung-dsim: " Luca Ceresoli
2026-05-19 10:37 ` [PATCH 34/37] drm/bridge: ti-sn65dsi83: " Luca Ceresoli
2026-05-19 10:37 ` [PATCH 35/37] drm/bridge: drm_bridge_attach(): don't fail on -EPROBE_DEFER Luca Ceresoli
2026-05-19 10:37 ` [PATCH 36/37] drm/display: bridge-connector: handle bridge hotplug Luca Ceresoli
2026-05-19 10:37 ` [PATCH 37/37] drm/mxsfb/lcdif: enable " Luca Ceresoli
2026-06-01 15:44 ` [PATCH 00/37] drm " Luca Ceresoli
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