linux-kernel - [PATCH v4 04/15] drm/atomic: Introduce helper to lookup connector by encoder

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Message-Id: <20250225-bridge-connector-v4-4-7ecb07b09cad@kernel.org>
Date: Tue, 25 Feb 2025 17:43:52 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
 Simona Vetter <simona@...ll.ch>, Andrzej Hajda <andrzej.hajda@...el.com>, 
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
 Douglas Anderson <dianders@...omium.org>
Cc: Herve Codina <herve.codina@...tlin.com>, 
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Maxime Ripard <mripard@...nel.org>, Simona Vetter <simona.vetter@...ll.ch>
Subject: [PATCH v4 04/15] drm/atomic: Introduce helper to lookup connector
 by encoder

With the bridges switching over to drm_bridge_connector, the direct
association between a bridge driver and its connector was lost.

This is mitigated for atomic bridge drivers by the fact you can access
the encoder, and then call drm_atomic_get_old_connector_for_encoder() or
drm_atomic_get_new_connector_for_encoder() with drm_atomic_state.

This was also made easier by providing drm_atomic_state directly to all
atomic hooks bridges can implement.

However, bridge drivers don't have a way to access drm_atomic_state
outside of the modeset path, like from the hotplug interrupt path or any
interrupt handler.

Let's introduce a function to retrieve the connector currently assigned
to an encoder, without using drm_atomic_state, to make these drivers'
life easier.

Co-developed-by: Simona Vetter <simona.vetter@...ll.ch>
Signed-off-by: Maxime Ripard <mripard@...nel.org>
---
 drivers/gpu/drm/drm_atomic.c | 45 ++++++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_atomic.h     |  3 +++
 2 files changed, 48 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 9ea2611770f43ce7ccba410406d5f2c528aab022..b926b132590e78f8d41d48eb4da4bccf170ee236 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -985,10 +985,55 @@ drm_atomic_get_new_connector_for_encoder(const struct drm_atomic_state *state,
 
 	return NULL;
 }
 EXPORT_SYMBOL(drm_atomic_get_new_connector_for_encoder);
 
+/**
+ * drm_atomic_get_connector_for_encoder - Get connector currently assigned to an encoder
+ * @encoder: The encoder to find the connector of
+ * @ctx: Modeset locking context
+ *
+ * This function finds and returns the connector currently assigned to
+ * an @encoder.
+ *
+ * Returns:
+ * The connector connected to @encoder, or an error pointer otherwise.
+ * When the error is EDEADLK, a deadlock has been detected and the
+ * sequence must be restarted.
+ */
+struct drm_connector *
+drm_atomic_get_connector_for_encoder(const struct drm_encoder *encoder,
+				     struct drm_modeset_acquire_ctx *ctx)
+{
+	struct drm_connector_list_iter conn_iter;
+	struct drm_connector *out_connector = ERR_PTR(-EINVAL);
+	struct drm_connector *connector;
+	struct drm_device *dev = encoder->dev;
+	int ret;
+
+	ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
+	if (ret)
+		return ERR_PTR(ret);
+
+	drm_connector_list_iter_begin(dev, &conn_iter);
+	drm_for_each_connector_iter(connector, &conn_iter) {
+		if (!connector->state)
+			continue;
+
+		if (encoder == connector->state->best_encoder) {
+			out_connector = connector;
+			break;
+		}
+	}
+	drm_connector_list_iter_end(&conn_iter);
+	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+	return out_connector;
+}
+EXPORT_SYMBOL(drm_atomic_get_connector_for_encoder);
+
+
 /**
  * drm_atomic_get_old_crtc_for_encoder - Get old crtc for an encoder
  * @state: Atomic state
  * @encoder: The encoder to fetch the crtc state for
  *
diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
index 4c673f0698fef6b60f77db980378d5e88e0e250e..38636a593c9d98cadda85ccd67326cb152f0dd27 100644
--- a/include/drm/drm_atomic.h
+++ b/include/drm/drm_atomic.h
@@ -623,10 +623,13 @@ struct drm_connector *
 drm_atomic_get_old_connector_for_encoder(const struct drm_atomic_state *state,
 					 struct drm_encoder *encoder);
 struct drm_connector *
 drm_atomic_get_new_connector_for_encoder(const struct drm_atomic_state *state,
 					 struct drm_encoder *encoder);
+struct drm_connector *
+drm_atomic_get_connector_for_encoder(const struct drm_encoder *encoder,
+				     struct drm_modeset_acquire_ctx *ctx);
 
 struct drm_crtc *
 drm_atomic_get_old_crtc_for_encoder(struct drm_atomic_state *state,
 					 struct drm_encoder *encoder);
 struct drm_crtc *

-- 
2.48.1