[PATCH v3 13/21] drm/bridge: Add the drm_bridge_chain_get_prev_bridge() helper

[Boris Brezillon]

Will be useful for bridge drivers that want to do bus format
negotiation with their neighbours.

Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
---
Changes in v3:
* Inline drm_bridge_chain_get_prev_bridge()
* Fix the doc

Changes in v2:
* Fix the kerneldoc
* Drop the !bridge || !bridge->encoder check
---
 include/drm/drm_bridge.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 2beb1ef9a733..3fb518494640 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -526,6 +526,22 @@ drm_bridge_chain_get_next_bridge(struct drm_bridge *bridge)
 	return list_next_entry(bridge, chain_node);
 }
 
+/**
+ * drm_bridge_chain_get_prev_bridge() - Get the previous bridge in the chain
+ * @bridge: bridge object
+ *
+ * RETURNS:
+ * the previous bridge in the chain, or NULL if @bridge is the first.
+ */
+static inline struct drm_bridge *
+drm_bridge_chain_get_prev_bridge(struct drm_bridge *bridge)
+{
+	if (list_is_first(&bridge->chain_node, &bridge->encoder->bridge_chain))
+		return NULL;
+
+	return list_prev_entry(bridge, chain_node);
+}
+
 /**
  * drm_bridge_chain_get_first_bridge() - Get the first bridge in the chain
  * @encoder: encoder object
-- 
2.21.0