[PATCH v2 03/16] drm/atomic: Add new atomic_create_state callback to drm_private_obj

[Maxime Ripard <mripard@kernel.org>]

The drm_private_obj initialization was inconsistent with the rest of the
KMS objects. Indeed, it required to pass a preallocated state in
drm_private_obj_init(), while all the others objects would have a reset
callback that would be called later on to create the state.

However, reset really is meant to reset the hardware and software state.
That it creates an initial state is a side-effect that has been used in
all objects but drm_private_obj. This is made more complex since some
drm_private_obj, the DisplayPort ones in particular, need to be
persistent across and suspend/resume cycle, and such a cycle would call
drm_mode_config_reset().

Thus, we need to add a new callback to allocate a pristine state for a
given private object.

This discussion has also came up during the atomic state readout
discussion, so it might be introduced into the other objects later on.

Until all drivers are converted to that new allocation pattern, we will
only call it if the passed state is NULL. This will be removed
eventually.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
 drivers/gpu/drm/drm_atomic.c | 20 ++++++++++++++++++--
 include/drm/drm_atomic.h     | 13 +++++++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index a5c5617266ae1dfe6038baeee6dfa3828c626683..36b56c71cb4e1ddc57577df724efe7d89b4fb6a9 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -793,15 +793,31 @@ int drm_atomic_private_obj_init(struct drm_device *dev,
 	memset(obj, 0, sizeof(*obj));
 
 	drm_modeset_lock_init(&obj->lock);
 
 	obj->dev = dev;
-	obj->state = state;
 	obj->funcs = funcs;
 	list_add_tail(&obj->head, &dev->mode_config.privobj_list);
 
-	state->obj = obj;
+	/*
+	 * Not all users of drm_atomic_private_obj_init have been
+	 * converted to using &drm_private_obj_funcs.reset yet. For the
+	 * time being, let's only call reset if the passed state is
+	 * NULL. Otherwise, we will fallback to the previous behaviour.
+	 */
+	if (!state) {
+		if (obj->funcs->atomic_create_state) {
+			state = obj->funcs->atomic_create_state(obj);
+			if (IS_ERR(state))
+				return PTR_ERR(state);
+
+			obj->state = state;
+		}
+	} else {
+		obj->state = state;
+		state->obj = obj;
+	}
 
 	return 0;
 }
 EXPORT_SYMBOL(drm_atomic_private_obj_init);
 
diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
index 9b3fb98b1e88c38877abdcb9df4d1c9540768833..10a71c4b6afc316f07023756be4cd3ed1d1d2974 100644
--- a/include/drm/drm_atomic.h
+++ b/include/drm/drm_atomic.h
@@ -205,10 +205,23 @@ struct drm_private_state;
  * added to the atomic states is expected to have an implementation of these
  * hooks and pass a pointer to its drm_private_state_funcs struct to
  * drm_atomic_get_private_obj_state().
  */
 struct drm_private_state_funcs {
+	/**
+	 * @atomic_create_state:
+	 *
+	 * Allocates a pristine, initialized, state for the private
+	 * object and returns it.
+	 *
+	 * RETURNS:
+	 *
+	 * A new, pristine, private state instance or an error pointer
+	 * on failure.
+	 */
+	struct drm_private_state *(*atomic_create_state)(struct drm_private_obj *obj);
+
 	/**
 	 * @atomic_duplicate_state:
 	 *
 	 * Duplicate the current state of the private object and return it. It
 	 * is an error to call this before obj->state has been initialized.

-- 
2.51.0