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.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>
Tested-by: Herve Codina <herve.codina@bootlin.com>
Co-developed-by: Simona Vetter <simona.vetter@intel.com>
Signed-off-by: Simona Vetter <simona.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250313-bridge-connector-v6-4-511c54a604fb@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>

1 files changed, 59 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 9ea2611770f4..0138cf0b8b63 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -933,6 +933,9 @@ EXPORT_SYMBOL(drm_atomic_get_new_private_obj_state);
  * state). This is especially true in enable hooks because the pipeline has
  * changed.
  *
+ * If you don't have access to the atomic state, see
+ * drm_atomic_get_connector_for_encoder().
+ *
  * Returns: The old connector connected to @encoder, or NULL if the encoder is
  * not connected.
  */
@@ -967,6 +970,9 @@ EXPORT_SYMBOL(drm_atomic_get_old_connector_for_encoder);
  * attached to @encoder vs ones that do (and to inspect their state). This is
  * especially true in disable hooks because the pipeline will change.
  *
+ * If you don't have access to the atomic state, see
+ * drm_atomic_get_connector_for_encoder().
+ *
  * Returns: The new connector connected to @encoder, or NULL if the encoder is
  * not connected.
  */
@@ -988,6 +994,59 @@ drm_atomic_get_new_connector_for_encoder(const struct drm_atomic_state *state,
 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.
+ *
+ * It is similar to the drm_atomic_get_old_connector_for_encoder() and
+ * drm_atomic_get_new_connector_for_encoder() helpers, but doesn't
+ * require access to the atomic state. If you have access to it, prefer
+ * using these. This helper is typically useful in situations where you
+ * don't have access to the atomic state, like detect, link repair,
+ * threaded interrupt handlers, or hooks from other frameworks (ALSA,
+ * CEC, etc.).
+ *
+ * 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