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

[Ajay kumar]

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