/* SPDX-License-Identifier: MIT */
/*
 * Copyright © 2023 Intel Corporation
 */

#ifndef __I915_GEM_OBJECT_FRONTBUFFER_H__
#define __I915_GEM_OBJECT_FRONTBUFFER_H__

#include <linux/kref.h>
#include <linux/rcupdate.h>

#include "display/intel_frontbuffer.h"
#include "i915_gem_object_types.h"

struct i915_frontbuffer {
        struct intel_frontbuffer base;
        struct drm_i915_gem_object *obj;
        struct i915_active write;
        struct rcu_head rcu;
        struct kref ref;
};

void __i915_gem_object_flush_frontbuffer(struct drm_i915_gem_object *obj,
                                         enum fb_op_origin origin);
void __i915_gem_object_invalidate_frontbuffer(struct drm_i915_gem_object *obj,
                                              enum fb_op_origin origin);

static inline void
i915_gem_object_flush_frontbuffer(struct drm_i915_gem_object *obj,
                                  enum fb_op_origin origin)
{
        if (unlikely(rcu_access_pointer(obj->frontbuffer)))
                __i915_gem_object_flush_frontbuffer(obj, origin);
}

static inline void
i915_gem_object_invalidate_frontbuffer(struct drm_i915_gem_object *obj,
                                       enum fb_op_origin origin)
{
        if (unlikely(rcu_access_pointer(obj->frontbuffer)))
                __i915_gem_object_invalidate_frontbuffer(obj, origin);
}

struct i915_frontbuffer *i915_gem_object_frontbuffer_get(struct drm_i915_gem_object *obj);
void i915_gem_object_frontbuffer_ref(struct i915_frontbuffer *front);
void i915_gem_object_frontbuffer_put(struct i915_frontbuffer *front);

/**
 * i915_gem_object_frontbuffer_lookup - Look up the object's frontbuffer
 * @obj: The object whose frontbuffer to look up.
 *
 * Get pointer to object's frontbuffer if such exists. Please note that RCU
 * mechanism is used to handle e.g. ongoing removal of frontbuffer pointer.
 *
 * Return: pointer to object's frontbuffer is such exists or NULL
 */
static inline struct i915_frontbuffer *
i915_gem_object_frontbuffer_lookup(const struct drm_i915_gem_object *obj)
{
        struct i915_frontbuffer *front;

        if (likely(!rcu_access_pointer(obj->frontbuffer)))
                return NULL;

        rcu_read_lock();
        do {
                front = rcu_dereference(obj->frontbuffer);
                if (!front)
                        break;

                if (unlikely(!kref_get_unless_zero(&front->ref)))
                        continue;

                if (likely(front == rcu_access_pointer(obj->frontbuffer)))
                        break;

                i915_gem_object_frontbuffer_put(front);
        } while (1);
        rcu_read_unlock();

        return front;
}

#endif