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 23/37] drm/encoder: add drm_encoder_cleanup_from()
Date: Tue, 19 May 2026 12:37:40 +0200 [thread overview]
Message-ID: <20260519-drm-bridge-hotplug-v1-23-45e2bdb3dfb4@bootlin.com> (raw)
In-Reply-To: <20260519-drm-bridge-hotplug-v1-0-45e2bdb3dfb4@bootlin.com>
Supporting hardware whose final part of the DRM pipeline can be physically
removed requires the ability to detach all bridges from a given point to
the end of the pipeline.
Introduce a variant of drm_encoder_cleanup() for this.
Take care to not try detaching non-attached bridges. This is needed because
when two or more bridges are removed not in the backwards order,
drm_encoder_cleanup_from() is called more than once for bridges closer to
the panel.
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin•com>
---
Note: in theory drm_encoder_cleanup() is now a superset of
drm_encoder_cleanup_from() and may be simplified to just call
drm_encoder_cleanup_from() and then do the extra actions. However the
common code is subtly different in terms of locking and checks, so this
would complicate the code in this patch and has thus been kept separate for
the time being to make reviewing sompler. Reimplementing
drm_encoder_cleanup() by using drm_encoder_cleanup_from() cvacn be done
later on.
A much simpler and now obsolete version of this patch (missing locking and
checks) previously appeared in
https://lore.kernel.org/lkml/20250206-hotplug-drm-bridge-v6-13-9d6f2c9c3058@bootlin.com/
---
drivers/gpu/drm/drm_encoder.c | 38 ++++++++++++++++++++++++++++++++++++++
include/drm/drm_encoder.h | 1 +
2 files changed, 39 insertions(+)
diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
index 0d5dbed06db4..40ece477b302 100644
--- a/drivers/gpu/drm/drm_encoder.c
+++ b/drivers/gpu/drm/drm_encoder.c
@@ -179,6 +179,44 @@ int drm_encoder_init(struct drm_device *dev,
}
EXPORT_SYMBOL(drm_encoder_init);
+/**
+ * drm_encoder_cleanup_from - remove a given bridge and all the following
+ * @encoder: encoder whole list of bridges shall be pruned
+ * @bridge: first bridge to remove
+ *
+ * Removes from an encoder all the bridges starting with a given bridge
+ * and until the end of the chain.
+ *
+ * Does nothing if the bridge is not attached to an encoder chain.
+ *
+ * This should not be used in "normal" DRM pipelines. It is only useful for
+ * devices whose final part of the DRM chain can be physically removed and
+ * later reconnected (possibly with different hardware).
+ */
+void drm_encoder_cleanup_from(struct drm_encoder *encoder, struct drm_bridge *bridge)
+{
+ struct drm_bridge *next;
+ LIST_HEAD(tmplist);
+
+ /*
+ * We need the bridge_chain_mutex to modify the chain, but
+ * drm_bridge_detach() will call DRM_MODESET_LOCK_ALL_BEGIN() (in
+ * drm_modeset_lock_fini()), resulting in a possible ABBA circular
+ * deadlock. Avoid it by first moving all the bridges to a
+ * temporary list holding the lock, and then calling
+ * drm_bridge_detach() without the lock.
+ */
+ mutex_lock(&encoder->bridge_chain_mutex);
+ if (!list_empty(&bridge->chain_node))
+ list_for_each_entry_safe_from(bridge, next, &encoder->bridge_chain, chain_node)
+ list_move_tail(&bridge->chain_node, &tmplist);
+ mutex_unlock(&encoder->bridge_chain_mutex);
+
+ while (!list_empty(&tmplist))
+ drm_bridge_detach(list_first_entry(&tmplist, struct drm_bridge, chain_node));
+}
+EXPORT_SYMBOL(drm_encoder_cleanup_from);
+
/**
* drm_encoder_cleanup - cleans up an initialised encoder
* @encoder: encoder to cleanup
diff --git a/include/drm/drm_encoder.h b/include/drm/drm_encoder.h
index eded7c34481a..d2a59f95692f 100644
--- a/include/drm/drm_encoder.h
+++ b/include/drm/drm_encoder.h
@@ -324,6 +324,7 @@ static inline struct drm_encoder *drm_encoder_find(struct drm_device *dev,
}
void drm_encoder_cleanup(struct drm_encoder *encoder);
+void drm_encoder_cleanup_from(struct drm_encoder *encoder, struct drm_bridge *bridge);
/**
* drm_for_each_encoder_mask - iterate over encoders specified by bitmask
--
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 ` Luca Ceresoli [this message]
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 ` [PATCH 30/37] drm/bridge: add drm_bridge_is_tail() to know whether a bridge completes the pipeline Luca Ceresoli
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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