[PATCH 3/4] drm/encoder: add drm_encoder_cleanup_from()

[Luca Ceresoli <luca.ceresoli@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.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
 drivers/gpu/drm/drm_encoder.c | 21 +++++++++++++++++++++
 include/drm/drm_encoder.h     |  1 +
 2 files changed, 22 insertions(+)

diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
index 8f2bc6a28482..13149447bec8 100644
--- a/drivers/gpu/drm/drm_encoder.c
+++ b/drivers/gpu/drm/drm_encoder.c
@@ -207,6 +207,27 @@ void drm_encoder_cleanup(struct drm_encoder *encoder)
 }
 EXPORT_SYMBOL(drm_encoder_cleanup);
 
+/**
+ * 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 bridges
+ * and until the end of the 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_for_each_entry_safe_from(bridge, next, &encoder->bridge_chain, chain_node)
+		drm_bridge_detach(bridge);
+}
+EXPORT_SYMBOL(drm_encoder_cleanup_from);
+
 static void drmm_encoder_alloc_release(struct drm_device *dev, void *ptr)
 {
 	struct drm_encoder *encoder = ptr;
diff --git a/include/drm/drm_encoder.h b/include/drm/drm_encoder.h
index 977a9381c8ba..bafcabb24267 100644
--- a/include/drm/drm_encoder.h
+++ b/include/drm/drm_encoder.h
@@ -320,6 +320,7 @@ 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

-- 
2.34.1