Will be useful for bridge drivers that want to do bus format
negotiation with their neighbours.
Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_bridge.c | 19 +++++++++++++++++++
include/drm/drm_bridge.h | 2 ++
2 files changed, 21 insertions(+)
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index dcad661daa74..9efb27087e70 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -271,6 +271,25 @@ drm_bridge_chain_get_next_bridge(struct drm_bridge *bridge)
}
EXPORT_SYMBOL(drm_bridge_chain_get_next_bridge);
+/**
+ * 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 there's @bridge is the
+ * last.
+ */
+struct drm_bridge *
+drm_bridge_chain_get_prev_bridge(struct drm_bridge *bridge)
+{
+ if (!bridge || !bridge->encoder ||
+ list_is_first(&bridge->encoder->bridge_chain, &bridge->chain_node))
+ return NULL;
+
+ return list_prev_entry(bridge, chain_node);
+}
+EXPORT_SYMBOL(drm_bridge_chain_get_prev_bridge);
+
/**
* DOC: bridge callbacks
*
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 5d8fe3709bde..2f69adb7b0f3 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -485,6 +485,8 @@ struct drm_bridge *
drm_bridge_chain_get_last_bridge(struct drm_encoder *encoder);
struct drm_bridge *
drm_bridge_chain_get_next_bridge(struct drm_bridge *bridge);
+struct drm_bridge *
+drm_bridge_chain_get_prev_bridge(struct drm_bridge *bridge);
bool drm_bridge_chain_mode_fixup(struct drm_encoder *encoder,
const struct drm_display_mode *mode,
struct drm_display_mode *adjusted_mode);
--
2.21.0
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