For bridge hotplug we need to successfully probe a card with an incomplete bridge chain, i.e. a chain whose last bridge currently in bridge_chain needs a next_bridge to work. Such a card would have no connector, and be able to add one as soon as the followong bridges are added up to the tail bridge (e.g. a panel_bridge or a connector_bridge).
Currently common DRM code is unable to tell whether the last bridge currently in the chain is the tail bridge (= the pipeline is complete) or not. Add drm_bridge_is_tail(), and a .is_tail func for it to rely on, so common code can know whether a bridge is a tail bridge or needs a next_bridge. Signed-off-by: Luca Ceresoli <[email protected]> --- drivers/gpu/drm/drm_bridge.c | 28 ++++++++++++++++++++++++++++ include/drm/drm_bridge.h | 19 +++++++++++++++++++ 2 files changed, 47 insertions(+) diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c index c62d17e84d4f..2b539c9749a6 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -646,6 +646,34 @@ void drm_bridge_detach(struct drm_bridge *bridge) drm_bridge_put(bridge); } +/** + * drm_bridge_is_tail - check whether the bridge is the last required to + * have a full pipeline + * @bridge: the bridge to check + * + * Tell whether this is a tail bridge, i.e. a bridge that does not need a + * next bridge to work. E.g. a panel_bridge is final, a DSI-to-LVDS bridge + * is not. + * + * In case of hotplug the last bridge currently in the chain (as in + * drm_bridge_chain_get_last_bridge()) might not be final, and be waiting + * for a pipeline tail to be connected. + * + * Return: true if this bridge does not need a next bridge to work, false + * otherwise + */ +bool drm_bridge_is_tail(struct drm_bridge *bridge) +{ + if (!(bridge->ops & DRM_BRIDGE_OP_IS_TAIL)) { + drm_warn_once(bridge->dev, "is_tail func not implemented by bridge %ps!", + bridge->funcs); + return false; + } + + return bridge->funcs->is_tail(bridge); +} +EXPORT_SYMBOL(drm_bridge_is_tail); + /** * DOC: bridge operations * diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h index 4ba3a5deef9a..d783a6fb93a0 100644 --- a/include/drm/drm_bridge.h +++ b/include/drm/drm_bridge.h @@ -78,6 +78,19 @@ struct drm_bridge_funcs { int (*attach)(struct drm_bridge *bridge, struct drm_encoder *encoder, enum drm_bridge_attach_flags flags); + /** + * @is_tail: + * + * Returns true if this is a tail bridge, i.e. it does not need a + * next bridge to work. E.g. a panel_bridge is a tail bridge, a + * DSI-to-LVDS bridge is not a tail bridge (no matter whether the + * next bridge is present or not). + * + * The @is_tail callback is optional but it is required if the + * bridge is part of a pipeline with hot-pluggable components. + */ + bool (*is_tail)(struct drm_bridge *bridge); + /** * @destroy: * @@ -1092,6 +1105,11 @@ enum drm_bridge_ops { * &drm_bridge_funcs->hdmi_clear_spd_infoframe callbacks. */ DRM_BRIDGE_OP_HDMI_SPD_INFOFRAME = BIT(10), + /** + * @DRM_BRIDGE_OP_IS_TAIL: The bridge implements the + * &drm_bridge_funcs->is_tail callback. + */ + DRM_BRIDGE_OP_IS_TAIL = BIT(11), }; /** @@ -1323,6 +1341,7 @@ void drm_bridge_remove(struct drm_bridge *bridge); int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge, struct drm_bridge *previous, enum drm_bridge_attach_flags flags); +bool drm_bridge_is_tail(struct drm_bridge *bridge); #ifdef CONFIG_OF struct drm_bridge *of_drm_find_and_get_bridge(struct device_node *np); -- 2.54.0
