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

[Ajay Kumar]

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 at 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