drm/bridge: Add a drm_bridge_state object

One of the last remaining objects to not have its atomic state.

This is being motivated by our attempt to support runtime bus-format
negotiation between elements of the bridge chain.
This patch just paves the road for such a feature by adding a new
drm_bridge_state object inheriting from drm_private_obj so we can
re-use some of the existing state initialization/tracking logic.

v10:
* Add changelog to the commit message

v9:
* Clarify the fact that the bridge->atomic_reset() and
  {connector,plane,crtc,...}->reset() semantics are different
* Move the drm_atomic_private_obj_init() call back to
  drm_bridge_attach()
* Check the presence of ->atomic_duplicate_state instead of
  ->atomic_reset in drm_atomic_add_encoder_bridges()
* Fix copy&paste errors in the atomic bridge state helpers doc
* Add A-b/R-b tags

v8:
* Move bridge state helpers out of the CONFIG_DEBUGFS section

v7:
* Move helpers, struct-defs, ... to atomic helper files to avoid the
  drm -> drm_kms_helper -> drm circular dep
* Stop providing default implementation for atomic state reset,
  duplicate and destroy hooks (has to do with the helper/core split)
* Drop all R-b/T-b as helpers have now be moved to other places

v6:
* Made helpers private, removed doc and moved them to satisfy dependencies
* Renamed helpers to _default_

v5:
* Re-introduced the helpers from v4

v4:
* Fix the doc
* Kill default helpers (inlined)
* Fix drm_atomic_get_bridge_state() to check for an ERR_PTR()
* Add Neil's R-b

v3:
* No changes

v2:
* Use drm_for_each_bridge_in_chain()
* Rename helpers to be more consistent with the rest of the DRM API
* Improve/fix the doc

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200128135514.108171-2-boris.brezillon@collabora.com

1 files changed, 103 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
index 7cf3cf936547..33141d2cdad4 100644
--- a/drivers/gpu/drm/drm_atomic_state_helper.c
+++ b/drivers/gpu/drm/drm_atomic_state_helper.c
@@ -26,6 +26,7 @@
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_state_helper.h>
+#include <drm/drm_bridge.h>
 #include <drm/drm_connector.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_device.h>
@@ -551,3 +552,105 @@ void __drm_atomic_helper_private_obj_duplicate_state(struct drm_private_obj *obj
 	memcpy(state, obj->state, sizeof(*state));
 }
 EXPORT_SYMBOL(__drm_atomic_helper_private_obj_duplicate_state);
+
+/**
+ * __drm_atomic_helper_bridge_duplicate_state() - Copy atomic bridge state
+ * @bridge: bridge object
+ * @state: atomic bridge state
+ *
+ * Copies atomic state from a bridge's current state and resets inferred values.
+ * This is useful for drivers that subclass the bridge state.
+ */
+void __drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge,
+						struct drm_bridge_state *state)
+{
+	__drm_atomic_helper_private_obj_duplicate_state(&bridge->base,
+							&state->base);
+	state->bridge = bridge;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_bridge_duplicate_state);
+
+/**
+ * drm_atomic_helper_bridge_duplicate_state() - Duplicate a bridge state object
+ * @bridge: bridge object
+ *
+ * Allocates a new bridge state and initializes it with the current bridge
+ * state values. This helper is meant to be used as a bridge
+ * &drm_bridge_funcs.atomic_duplicate_state hook for bridges that don't
+ * subclass the bridge state.
+ */
+struct drm_bridge_state *
+drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge)
+{
+	struct drm_bridge_state *new;
+
+	if (WARN_ON(!bridge->base.state))
+		return NULL;
+
+	new = kzalloc(sizeof(*new), GFP_KERNEL);
+	if (new)
+		__drm_atomic_helper_bridge_duplicate_state(bridge, new);
+
+	return new;
+}
+EXPORT_SYMBOL(drm_atomic_helper_bridge_duplicate_state);
+
+/**
+ * drm_atomic_helper_bridge_destroy_state() - Destroy a bridge state object
+ * @bridge: the bridge this state refers to
+ * @state: bridge state to destroy
+ *
+ * Destroys a bridge state previously created by
+ * &drm_atomic_helper_bridge_reset() or
+ * &drm_atomic_helper_bridge_duplicate_state(). This helper is meant to be
+ * used as a bridge &drm_bridge_funcs.atomic_destroy_state hook for bridges
+ * that don't subclass the bridge state.
+ */
+void drm_atomic_helper_bridge_destroy_state(struct drm_bridge *bridge,
+					    struct drm_bridge_state *state)
+{
+	kfree(state);
+}
+EXPORT_SYMBOL(drm_atomic_helper_bridge_destroy_state);
+
+/**
+ * __drm_atomic_helper_bridge_reset() - Initialize a bridge state to its
+ *					default
+ * @bridge: the bridge this state refers to
+ * @state: bridge state to initialize
+ *
+ * Initializes the bridge state to default values. This is meant to be called
+ * by the bridge &drm_bridge_funcs.atomic_reset hook for bridges that subclass
+ * the bridge state.
+ */
+void __drm_atomic_helper_bridge_reset(struct drm_bridge *bridge,
+				      struct drm_bridge_state *state)
+{
+	memset(state, 0, sizeof(*state));
+	state->bridge = bridge;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_bridge_reset);
+
+/**
+ * drm_atomic_helper_bridge_reset() - Allocate and initialize a bridge state
+ *				      to its default
+ * @bridge: the bridge this state refers to
+ * @state: bridge state to initialize
+ *
+ * Allocates the bridge state and initializes it to default values. This helper
+ * is meant to be used as a bridge &drm_bridge_funcs.atomic_reset hook for
+ * bridges that don't subclass the bridge state.
+ */
+struct drm_bridge_state *
+drm_atomic_helper_bridge_reset(struct drm_bridge *bridge)
+{
+	struct drm_bridge_state *bridge_state;
+
+	bridge_state = kzalloc(sizeof(*bridge_state), GFP_KERNEL);
+	if (!bridge_state)
+		return ERR_PTR(-ENOMEM);
+
+	__drm_atomic_helper_bridge_reset(bridge, bridge_state);
+	return bridge_state;
+}
+EXPORT_SYMBOL(drm_atomic_helper_bridge_reset);