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

[Sean Paul]

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().

Sean


>  {
> +       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
>