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

On Wed, May 7, 2014 at 1:33 AM, Sean Paul seanpaul@chromium.org wrote:

On Tue, May 6, 2014 at 12:45 PM, Ajay kumar ajaynumb@gmail.com wrote:

...

Sean,

On Tue, May 6, 2014 at 9:25 PM, Sean Paul seanpaul@chromium.org wrote:

...

On Mon, May 5, 2014 at 12:52 PM, Ajay Kumar ajaykumar.rs@samsung.com wrote:

...

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)
  

IMO, we should let whoever is spawning the bridges chain them together, instead of passing encoder in init().

For this, we have to modify drm_bridge_init to return a bridge pointer

Sorry, I don't follow this. You are passing in the bridge pointer, so presumably you already have it.

Ahh, Sorry for that. It should be ptn3460_init, and not drm_bridge_init :) I mean, ptn3460_init shall return a bridge pointer and exynos_dp(encoder) should make use of it to prepare the bridge chain.

Ajay

Sean

...

and then, as Rob is suggesting, we can have some helper functions to update next_bridge ptr to form a bridge chain, and these functions can be called from the corresponding encoder implementation.

Ajay

...

...

{

•   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