From 19f5cd8f1ac608c9aa1f6ecdf1d9011f21296c96 Mon Sep 17 00:00:00 2001
From: Boris Brezillon <boris.brezillon@collabora.com>
Date: Tue, 3 Dec 2019 15:15:10 +0100
Subject: drm/bridge: Add the drm_bridge_get_prev_bridge() helper
Git-commit: ac877c64c87aff5d228cf53e40d8f68899afa815
Patch-mainline: v5.6-rc1
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322

The drm_bridge_get_prev_bridge() helper will be useful for bridge
drivers that want to do bus format negotiation with their neighbours.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191203141515.3597631-7-boris.brezillon@collabora.com
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 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 1eb854025a20..bfb0385163f1 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -426,6 +426,22 @@ drm_bridge_get_next_bridge(struct drm_bridge *bridge)
 	return list_next_entry(bridge, chain_node);
 }
 
+/**
+ * drm_bridge_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_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
-- 
2.28.0