/* 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"

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);
}

/**
 * i915_gem_object_get_frontbuffer - Get the object's frontbuffer
 * @obj: The object whose frontbuffer to get.
 *
 * 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 intel_frontbuffer *
i915_gem_object_get_frontbuffer(const struct drm_i915_gem_object *obj)
{
        struct intel_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;

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

        return front;
}

/**
 * i915_gem_object_set_frontbuffer - Set the object's frontbuffer
 * @obj: The object whose frontbuffer to set.
 * @front: The frontbuffer to set
 *
 * Set object's frontbuffer pointer. If frontbuffer is already set for the
 * object keep it and return it's pointer to the caller. Please note that RCU
 * mechanism is used to handle e.g. ongoing removal of frontbuffer pointer. This
 * function is protected by i915->display->fb_tracking.lock
 *
 * Return: pointer to frontbuffer which was set.
 */
static inline struct intel_frontbuffer *
i915_gem_object_set_frontbuffer(struct drm_i915_gem_object *obj,
                                struct intel_frontbuffer *front)
{
        struct intel_frontbuffer *cur = front;

        if (!front) {
                RCU_INIT_POINTER(obj->frontbuffer, NULL);
        } else if (rcu_access_pointer(obj->frontbuffer)) {
                cur = rcu_dereference_protected(obj->frontbuffer, true);
                kref_get(&cur->ref);
        } else {
                rcu_assign_pointer(obj->frontbuffer, front);
        }

        return cur;
}

#endif