text: #ifndef __DRM_GEM_H__
  #define __DRM_GEM_H__
  
  /*
   * GEM Graphics Execution Manager Driver Interfaces
   *
   * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
   * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
   * Copyright (c) 2009-2010, Code Aurora Forum.
   * All rights reserved.
   * Copyright © 2014 Intel Corporation
   *   Daniel Vetter <daniel.vetter@ffwll.ch>
   *
   * Author: Rickard E. (Rik) Faith <faith@valinux.com>
   * Author: Gareth Hughes <gareth@valinux.com>
   *
   * Permission is hereby granted, free of charge, to any person obtaining a
   * copy of this software and associated documentation files (the "Software"),
   * to deal in the Software without restriction, including without limitation
   * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   * and/or sell copies of the Software, and to permit persons to whom the
   * Software is furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice (including the next
   * paragraph) shall be included in all copies or substantial portions of the
   * Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
   * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
   * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
   * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
   * OTHER DEALINGS IN THE SOFTWARE.
   */
  
  /**
   * struct drm_gem_object - GEM buffer object
   *
   * This structure defines the generic parts for GEM buffer objects, which are
   * mostly around handling mmap and userspace handles.
   *
   * Buffer objects are often abbreviated to BO.
   */
  struct drm_gem_object {
  	/**
  	 * @refcount:
  	 *
  	 * Reference count of this object
  	 *
  	 * Please use drm_gem_object_reference() to acquire and
  	 * drm_gem_object_unreference() or drm_gem_object_unreference_unlocked()
  	 * to release a reference to a GEM buffer object.
  	 */
  	struct kref refcount;
  
  	/**
  	 * @handle_count:
  	 *
  	 * This is the GEM file_priv handle count of this object.
  	 *
  	 * Each handle also holds a reference. Note that when the handle_count
  	 * drops to 0 any global names (e.g. the id in the flink namespace) will
  	 * be cleared.
  	 *
  	 * Protected by &drm_device.object_name_lock.
  	 */
  	unsigned handle_count;
  
  	/**
  	 * @dev: DRM dev this object belongs to.
  	 */
  	struct drm_device *dev;
  
  	/**
  	 * @filp:
  	 *
  	 * SHMEM file node used as backing storage for swappable buffer objects.
  	 * GEM also supports driver private objects with driver-specific backing
  	 * storage (contiguous CMA memory, special reserved blocks). In this
  	 * case @filp is NULL.
  	 */
  	struct file *filp;
  
  	/**
  	 * @vma_node:
  	 *
  	 * Mapping info for this object to support mmap. Drivers are supposed to
  	 * allocate the mmap offset using drm_gem_create_mmap_offset(). The
  	 * offset itself can be retrieved using drm_vma_node_offset_addr().
  	 *
  	 * Memory mapping itself is handled by drm_gem_mmap(), which also checks
  	 * that userspace is allowed to access the object.
  	 */
  	struct drm_vma_offset_node vma_node;
  
  	/**
  	 * @size:
  	 *
  	 * Size of the object, in bytes.  Immutable over the object's
  	 * lifetime.
  	 */
  	size_t size;
  
  	/**
  	 * @name:
  	 *
  	 * Global name for this object, starts at 1. 0 means unnamed.
  	 * Access is covered by &drm_device.object_name_lock. This is used by
  	 * the GEM_FLINK and GEM_OPEN ioctls.
  	 */
  	int name;
  
  	/**
  	 * @read_domains:
  	 *
  	 * Read memory domains. These monitor which caches contain read/write data
  	 * related to the object. When transitioning from one set of domains
  	 * to another, the driver is called to ensure that caches are suitably
  	 * flushed and invalidated.
  	 */
  	uint32_t read_domains;
  
  	/**
  	 * @write_domain: Corresponding unique write memory domain.
  	 */
  	uint32_t write_domain;
  
  	/**
  	 * @pending_read_domains:
  	 *
  	 * While validating an exec operation, the
  	 * new read/write domain values are computed here.
  	 * They will be transferred to the above values
  	 * at the point that any cache flushing occurs
  	 */
  	uint32_t pending_read_domains;
  
  	/**
  	 * @pending_write_domain: Write domain similar to @pending_read_domains.
  	 */
  	uint32_t pending_write_domain;
  
  	/**
  	 * @dma_buf:
  	 *
  	 * dma-buf associated with this GEM object.
  	 *
  	 * Pointer to the dma-buf associated with this gem object (either
  	 * through importing or exporting). We break the resulting reference
  	 * loop when the last gem handle for this object is released.
  	 *
  	 * Protected by &drm_device.object_name_lock.
  	 */
  	struct dma_buf *dma_buf;
  
  	/**
  	 * @import_attach:
  	 *
  	 * dma-buf attachment backing this object.
  	 *
  	 * Any foreign dma_buf imported as a gem object has this set to the
  	 * attachment point for the device. This is invariant over the lifetime
  	 * of a gem object.
  	 *
  	 * The &drm_driver.gem_free_object callback is responsible for cleaning
  	 * up the dma_buf attachment and references acquired at import time.
  	 *
  	 * Note that the drm gem/prime core does not depend upon drivers setting
  	 * this field any more. So for drivers where this doesn't make sense
  	 * (e.g. virtual devices or a displaylink behind an usb bus) they can
  	 * simply leave it as NULL.
  	 */
  	struct dma_buf_attachment *import_attach;
  };
  
  void drm_gem_object_release(struct drm_gem_object *obj);
  void drm_gem_object_free(struct kref *kref);
  int drm_gem_object_init(struct drm_device *dev,
  			struct drm_gem_object *obj, size_t size);
  void drm_gem_private_object_init(struct drm_device *dev,
  				 struct drm_gem_object *obj, size_t size);
  void drm_gem_vm_open(struct vm_area_struct *vma);
  void drm_gem_vm_close(struct vm_area_struct *vma);
  int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
  		     struct vm_area_struct *vma);
  int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma);
  
  /**
   * drm_gem_object_reference - acquire a GEM BO reference
   * @obj: GEM buffer object
   *
   * This acquires additional reference to @obj. It is illegal to call this
   * without already holding a reference. No locks required.
   */
  static inline void
  drm_gem_object_reference(struct drm_gem_object *obj)
  {
  	kref_get(&obj->refcount);
  }
  
  /**
   * __drm_gem_object_unreference - raw function to release a GEM BO reference
   * @obj: GEM buffer object
   *
   * This function is meant to be used by drivers which are not encumbered with
   * &drm_device.struct_mutex legacy locking and which are using the
   * gem_free_object_unlocked callback. It avoids all the locking checks and
   * locking overhead of drm_gem_object_unreference() and
   * drm_gem_object_unreference_unlocked().
   *
   * Drivers should never call this directly in their code. Instead they should
   * wrap it up into a ``driver_gem_object_unreference(struct driver_gem_object
   * *obj)`` wrapper function, and use that. Shared code should never call this, to
   * avoid breaking drivers by accident which still depend upon
   * &drm_device.struct_mutex locking.
   */
  static inline void
  __drm_gem_object_unreference(struct drm_gem_object *obj)
  {
  	kref_put(&obj->refcount, drm_gem_object_free);
  }
  
  void drm_gem_object_unreference_unlocked(struct drm_gem_object *obj);
  void drm_gem_object_unreference(struct drm_gem_object *obj);
  
  int drm_gem_handle_create(struct drm_file *file_priv,
  			  struct drm_gem_object *obj,
  			  u32 *handlep);
  int drm_gem_handle_delete(struct drm_file *filp, u32 handle);
  
  
  void drm_gem_free_mmap_offset(struct drm_gem_object *obj);
  int drm_gem_create_mmap_offset(struct drm_gem_object *obj);
  int drm_gem_create_mmap_offset_size(struct drm_gem_object *obj, size_t size);
  
  struct page **drm_gem_get_pages(struct drm_gem_object *obj);
  void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
  		bool dirty, bool accessed);
  
  struct drm_gem_object *drm_gem_object_lookup(struct drm_file *filp, u32 handle);
  int drm_gem_dumb_destroy(struct drm_file *file,
  			 struct drm_device *dev,
  			 uint32_t handle);
  
  #endif /* __DRM_GEM_H__ */
  