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

[Sean Paul]

On Tue, May 6, 2014 at 12:45 PM, Ajay kumar <ajaynumb at gmail.com> wrote:
> Sean,
>
>
> On Tue, May 6, 2014 at 9:25 PM, Sean Paul <seanpaul at chromium.org> wrote:
>> On Mon, May 5, 2014 at 12:52 PM, Ajay Kumar <ajaykumar.rs at 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 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)
>>
>>
>> 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.

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
>>>