[RFC V2 1/3] drm: implement chaining of drm bridges

[Ajay Kumar <ajaykumar.rs@samsung.com>]

As of now, we can have only one bridge hanging off the encoder.
With this patch, we allow multiple bridges to hang onto the same encoder
with the use of a simple next_bridge ptr.

The drm core calls bridge->funcs for the first bridge which
is attached to it, and its upto the individual bridge drivers
to call bridge->funcs for the next bridge in the chain.

Signed-off-by: Ajay Kumar <ajaykumar.rs@samsung.com>
---
 drivers/gpu/drm/drm_crtc.c | 13 ++++++++++++-
 include/drm/drm_crtc.h     |  2 ++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index d8b7099..fe9905f 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -918,8 +918,10 @@ EXPORT_SYMBOL(drm_connector_unplug_all);
  * Zero on success, error code on failure.
  */
 int drm_bridge_init(struct drm_device *dev, struct drm_bridge *bridge,
-		const struct drm_bridge_funcs *funcs)
+			struct drm_encoder *encoder,
+			const struct drm_bridge_funcs *funcs)
 {
+	struct drm_bridge *temp;
 	int ret;
 
 	drm_modeset_lock_all(dev);
@@ -931,6 +933,15 @@ int drm_bridge_init(struct drm_device *dev, struct drm_bridge *bridge,
 	bridge->dev = dev;
 	bridge->funcs = funcs;
 
+	if (encoder->bridge) {
+		temp = encoder->bridge;
+		while (temp->next_bridge)
+			temp = temp->next_bridge;
+
+		temp->next_bridge = bridge;
+	} else
+		encoder->bridge = bridge;
+
 	list_add_tail(&bridge->head, &dev->mode_config.bridge_list);
 	dev->mode_config.num_bridge++;
 
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index e55fccb..bb6ed88 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -619,6 +619,7 @@ struct drm_bridge_funcs {
 struct drm_bridge {
 	struct drm_device *dev;
 	struct list_head head;
+	struct drm_bridge *next_bridge;
 
 	struct drm_mode_object base;
 
@@ -862,6 +863,7 @@ extern void drm_connector_cleanup(struct drm_connector *connector);
 extern void drm_connector_unplug_all(struct drm_device *dev);
 
 extern int drm_bridge_init(struct drm_device *dev, struct drm_bridge *bridge,
+			   struct drm_encoder *encoder,
 			   const struct drm_bridge_funcs *funcs);
 extern void drm_bridge_cleanup(struct drm_bridge *bridge);
 
-- 
1.8.1.2