drivers/gpu/drm/drm_prime.c - kernel/msm-4.19 - Gitiles

 /*
  * Copyright © 2012 Red Hat
  *
  * 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
  * THE AUTHORS OR COPYRIGHT HOLDERS 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.
  *
  * Authors:
  *      Dave Airlie <airlied@redhat.com>
  *      Rob Clark <rob.clark@linaro.org>
  *
  */

 #include <linux/export.h>
 #include <linux/dma-buf.h>
 #include <drm/drmP.h>

 /*
  * DMA-BUF/GEM Object references and lifetime overview:
  *
  * On the export the dma_buf holds a reference to the exporting GEM
  * object. It takes this reference in handle_to_fd_ioctl, when it
  * first calls .prime_export and stores the exporting GEM object in
  * the dma_buf priv. This reference is released when the dma_buf
  * object goes away in the driver .release function.
  *
  * On the import the importing GEM object holds a reference to the
  * dma_buf (which in turn holds a ref to the exporting GEM object).
  * It takes that reference in the fd_to_handle ioctl.
  * It calls dma_buf_get, creates an attachment to it and stores the
  * attachment in the GEM object. When this attachment is destroyed
  * when the imported object is destroyed, we remove the attachment
  * and drop the reference to the dma_buf.
  *
  * Thus the chain of references always flows in one direction
  * (avoiding loops): importing_gem -> dmabuf -> exporting_gem
  *
  * Self-importing: if userspace is using PRIME as a replacement for flink
  * then it will get a fd->handle request for a GEM object that it created.
  * Drivers should detect this situation and return back the gem object
  * from the dma-buf private.  Prime will do this automatically for drivers that
  * use the drm_gem_prime_{import,export} helpers.
  */

 struct drm_prime_member {
 	struct list_head entry;
 	struct dma_buf *dma_buf;
 	uint32_t handle;
 };

 struct drm_prime_attachment {
 	struct sg_table *sgt;
 	enum dma_data_direction dir;
 };

 static int drm_prime_add_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t handle)
 {
 	struct drm_prime_member *member;

 	member = kmalloc(sizeof(*member), GFP_KERNEL);
 	if (!member)
 		return -ENOMEM;

 	get_dma_buf(dma_buf);
 	member->dma_buf = dma_buf;
 	member->handle = handle;
 	list_add(&member->entry, &prime_fpriv->head);
 	return 0;
 }

 static int drm_gem_map_attach(struct dma_buf *dma_buf,
 			      struct device *target_dev,
 			      struct dma_buf_attachment *attach)
 {
 	struct drm_prime_attachment *prime_attach;
 	struct drm_gem_object *obj = dma_buf->priv;
 	struct drm_device *dev = obj->dev;

 	prime_attach = kzalloc(sizeof(*prime_attach), GFP_KERNEL);
 	if (!prime_attach)
 		return -ENOMEM;

 	prime_attach->dir = DMA_NONE;
 	attach->priv = prime_attach;

 	if (!dev->driver->gem_prime_pin)
 		return 0;

 	return dev->driver->gem_prime_pin(obj);
 }

 static void drm_gem_map_detach(struct dma_buf *dma_buf,
 			       struct dma_buf_attachment *attach)
 {
 	struct drm_prime_attachment *prime_attach = attach->priv;
 	struct drm_gem_object *obj = dma_buf->priv;
 	struct drm_device *dev = obj->dev;
 	struct sg_table *sgt;

 	if (dev->driver->gem_prime_unpin)
 		dev->driver->gem_prime_unpin(obj);

 	if (!prime_attach)
 		return;

 	sgt = prime_attach->sgt;

 	if (prime_attach->dir != DMA_NONE)
 		dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents,
 				prime_attach->dir);

 	sg_free_table(sgt);
 	kfree(sgt);
 	kfree(prime_attach);
 	attach->priv = NULL;
 }

 static struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach,
 		enum dma_data_direction dir)
 {
 	struct drm_prime_attachment *prime_attach = attach->priv;
 	struct drm_gem_object *obj = attach->dmabuf->priv;
 	struct sg_table *sgt;

 	if (WARN_ON(dir == DMA_NONE || !prime_attach))
 		return ERR_PTR(-EINVAL);

 	/* return the cached mapping when possible */
 	if (prime_attach->dir == dir)
 		return prime_attach->sgt;

 	/*
 	 * two mappings with different directions for the same attachment are
 	 * not allowed
 	 */
 	if (WARN_ON(prime_attach->dir != DMA_NONE))
 		return ERR_PTR(-EBUSY);

 	mutex_lock(&obj->dev->struct_mutex);

 	sgt = obj->dev->driver->gem_prime_get_sg_table(obj);

 	if (!IS_ERR(sgt)) {
 		if (!dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir)) {
 			sg_free_table(sgt);
 			kfree(sgt);
 			sgt = ERR_PTR(-ENOMEM);
 		} else {
 			prime_attach->sgt = sgt;
 			prime_attach->dir = dir;
 		}
 	}

 	mutex_unlock(&obj->dev->struct_mutex);
 	return sgt;
 }

 static void drm_gem_unmap_dma_buf(struct dma_buf_attachment *attach,
 		struct sg_table *sgt, enum dma_data_direction dir)
 {
 	/* nothing to be done here */
 }

 static void drm_gem_dmabuf_release(struct dma_buf *dma_buf)
 {
 	struct drm_gem_object *obj = dma_buf->priv;

 	if (obj->export_dma_buf == dma_buf) {
 		/* drop the reference on the export fd holds */
 		obj->export_dma_buf = NULL;
 		drm_gem_object_unreference_unlocked(obj);
 	}
 }

 static void *drm_gem_dmabuf_vmap(struct dma_buf *dma_buf)
 {
 	struct drm_gem_object *obj = dma_buf->priv;
 	struct drm_device *dev = obj->dev;

 	return dev->driver->gem_prime_vmap(obj);
 }

 static void drm_gem_dmabuf_vunmap(struct dma_buf *dma_buf, void *vaddr)
 {
 	struct drm_gem_object *obj = dma_buf->priv;
 	struct drm_device *dev = obj->dev;

 	dev->driver->gem_prime_vunmap(obj, vaddr);
 }

 static void *drm_gem_dmabuf_kmap_atomic(struct dma_buf *dma_buf,
 		unsigned long page_num)
 {
 	return NULL;
 }

 static void drm_gem_dmabuf_kunmap_atomic(struct dma_buf *dma_buf,
 		unsigned long page_num, void *addr)
 {

 }
 static void *drm_gem_dmabuf_kmap(struct dma_buf *dma_buf,
 		unsigned long page_num)
 {
 	return NULL;
 }

 static void drm_gem_dmabuf_kunmap(struct dma_buf *dma_buf,
 		unsigned long page_num, void *addr)
 {

 }

 static int drm_gem_dmabuf_mmap(struct dma_buf *dma_buf,
 		struct vm_area_struct *vma)
 {
 	return -EINVAL;
 }

 static const struct dma_buf_ops drm_gem_prime_dmabuf_ops =  {
 	.attach = drm_gem_map_attach,
 	.detach = drm_gem_map_detach,
 	.map_dma_buf = drm_gem_map_dma_buf,
 	.unmap_dma_buf = drm_gem_unmap_dma_buf,
 	.release = drm_gem_dmabuf_release,
 	.kmap = drm_gem_dmabuf_kmap,
 	.kmap_atomic = drm_gem_dmabuf_kmap_atomic,
 	.kunmap = drm_gem_dmabuf_kunmap,
 	.kunmap_atomic = drm_gem_dmabuf_kunmap_atomic,
 	.mmap = drm_gem_dmabuf_mmap,
 	.vmap = drm_gem_dmabuf_vmap,
 	.vunmap = drm_gem_dmabuf_vunmap,
 };

 /**
  * DOC: PRIME Helpers
  *
  * Drivers can implement @gem_prime_export and @gem_prime_import in terms of
  * simpler APIs by using the helper functions @drm_gem_prime_export and
  * @drm_gem_prime_import.  These functions implement dma-buf support in terms of
  * five lower-level driver callbacks:
  *
  * Export callbacks:
  *
  *  - @gem_prime_pin (optional): prepare a GEM object for exporting
  *
  *  - @gem_prime_get_sg_table: provide a scatter/gather table of pinned pages
  *
  *  - @gem_prime_vmap: vmap a buffer exported by your driver
  *
  *  - @gem_prime_vunmap: vunmap a buffer exported by your driver
  *
  * Import callback:
  *
  *  - @gem_prime_import_sg_table (import): produce a GEM object from another
  *    driver's scatter/gather table
  */

 struct dma_buf *drm_gem_prime_export(struct drm_device *dev,
 				     struct drm_gem_object *obj, int flags)
 {
 	return dma_buf_export(obj, &drm_gem_prime_dmabuf_ops, obj->size, flags);
 }
 EXPORT_SYMBOL(drm_gem_prime_export);

 int drm_gem_prime_handle_to_fd(struct drm_device *dev,
 		struct drm_file *file_priv, uint32_t handle, uint32_t flags,
 		int *prime_fd)
 {
 	struct drm_gem_object *obj;
 	void *buf;
 	int ret = 0;
 	struct dma_buf *dmabuf;

 	obj = drm_gem_object_lookup(dev, file_priv, handle);
 	if (!obj)
 		return -ENOENT;

 	mutex_lock(&file_priv->prime.lock);
 	/* re-export the original imported object */
 	if (obj->import_attach) {
 		dmabuf = obj->import_attach->dmabuf;
 		goto out_have_obj;
 	}

 	if (obj->export_dma_buf) {
 		dmabuf = obj->export_dma_buf;
 		goto out_have_obj;
 	}

 	buf = dev->driver->gem_prime_export(dev, obj, flags);
 	if (IS_ERR(buf)) {
 		/* normally the created dma-buf takes ownership of the ref,
 		 * but if that fails then drop the ref
 		 */
 		ret = PTR_ERR(buf);
 		goto out;
 	}
 	obj->export_dma_buf = buf;

 	/* if we've exported this buffer the cheat and add it to the import list
 	 * so we get the correct handle back
 	 */
 	ret = drm_prime_add_buf_handle(&file_priv->prime,
 				       obj->export_dma_buf, handle);
 	if (ret)
 		goto fail_put_dmabuf;

 	*prime_fd = dma_buf_fd(buf, flags);
 	mutex_unlock(&file_priv->prime.lock);
 	return 0;

 out_have_obj:
 	get_dma_buf(dmabuf);
 	*prime_fd = dma_buf_fd(dmabuf, flags);
 	goto out;

 fail_put_dmabuf:
 	/* clear NOT to be checked when releasing dma_buf */
 	obj->export_dma_buf = NULL;
 	dma_buf_put(buf);
 out:
 	drm_gem_object_unreference_unlocked(obj);
 	mutex_unlock(&file_priv->prime.lock);
 	return ret;
 }
 EXPORT_SYMBOL(drm_gem_prime_handle_to_fd);

 struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
 					    struct dma_buf *dma_buf)
 {
 	struct dma_buf_attachment *attach;
 	struct sg_table *sgt;
 	struct drm_gem_object *obj;
 	int ret;

 	if (!dev->driver->gem_prime_import_sg_table)
 		return ERR_PTR(-EINVAL);

 	if (dma_buf->ops == &drm_gem_prime_dmabuf_ops) {
 		obj = dma_buf->priv;
 		if (obj->dev == dev) {
 			/*
 			 * Importing dmabuf exported from out own gem increases
 			 * refcount on gem itself instead of f_count of dmabuf.
 			 */
 			drm_gem_object_reference(obj);
 			return obj;
 		}
 	}

 	attach = dma_buf_attach(dma_buf, dev->dev);
 	if (IS_ERR(attach))
 		return ERR_CAST(attach);

 	get_dma_buf(dma_buf);

 	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
 	if (IS_ERR_OR_NULL(sgt)) {
 		ret = PTR_ERR(sgt);
 		goto fail_detach;
 	}

 	obj = dev->driver->gem_prime_import_sg_table(dev, dma_buf->size, sgt);
 	if (IS_ERR(obj)) {
 		ret = PTR_ERR(obj);
 		goto fail_unmap;
 	}

 	obj->import_attach = attach;

 	return obj;

 fail_unmap:
 	dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
 fail_detach:
 	dma_buf_detach(dma_buf, attach);
 	dma_buf_put(dma_buf);

 	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL(drm_gem_prime_import);

 int drm_gem_prime_fd_to_handle(struct drm_device *dev,
 		struct drm_file *file_priv, int prime_fd, uint32_t *handle)
 {
 	struct dma_buf *dma_buf;
 	struct drm_gem_object *obj;
 	int ret;

 	dma_buf = dma_buf_get(prime_fd);
 	if (IS_ERR(dma_buf))
 		return PTR_ERR(dma_buf);

 	mutex_lock(&file_priv->prime.lock);

 	ret = drm_prime_lookup_buf_handle(&file_priv->prime,
 			dma_buf, handle);
 	if (!ret) {
 		ret = 0;
 		goto out_put;
 	}

 	/* never seen this one, need to import */
 	obj = dev->driver->gem_prime_import(dev, dma_buf);
 	if (IS_ERR(obj)) {
 		ret = PTR_ERR(obj);
 		goto out_put;
 	}

 	ret = drm_gem_handle_create(file_priv, obj, handle);
 	drm_gem_object_unreference_unlocked(obj);
 	if (ret)
 		goto out_put;

 	ret = drm_prime_add_buf_handle(&file_priv->prime,
 			dma_buf, *handle);
 	if (ret)
 		goto fail;

 	mutex_unlock(&file_priv->prime.lock);

 	dma_buf_put(dma_buf);

 	return 0;

 fail:
 	/* hmm, if driver attached, we are relying on the free-object path
 	 * to detach.. which seems ok..
 	 */
 	drm_gem_object_handle_unreference_unlocked(obj);
 out_put:
 	dma_buf_put(dma_buf);
 	mutex_unlock(&file_priv->prime.lock);
 	return ret;
 }
 EXPORT_SYMBOL(drm_gem_prime_fd_to_handle);

 int drm_prime_handle_to_fd_ioctl(struct drm_device *dev, void *data,
 				 struct drm_file *file_priv)
 {
 	struct drm_prime_handle *args = data;
 	uint32_t flags;

 	if (!drm_core_check_feature(dev, DRIVER_PRIME))
 		return -EINVAL;

 	if (!dev->driver->prime_handle_to_fd)
 		return -ENOSYS;

 	/* check flags are valid */
 	if (args->flags & ~DRM_CLOEXEC)
 		return -EINVAL;

 	/* we only want to pass DRM_CLOEXEC which is == O_CLOEXEC */
 	flags = args->flags & DRM_CLOEXEC;

 	return dev->driver->prime_handle_to_fd(dev, file_priv,
 			args->handle, flags, &args->fd);
 }

 int drm_prime_fd_to_handle_ioctl(struct drm_device *dev, void *data,
 				 struct drm_file *file_priv)
 {
 	struct drm_prime_handle *args = data;

 	if (!drm_core_check_feature(dev, DRIVER_PRIME))
 		return -EINVAL;

 	if (!dev->driver->prime_fd_to_handle)
 		return -ENOSYS;

 	return dev->driver->prime_fd_to_handle(dev, file_priv,
 			args->fd, &args->handle);
 }

 /*
  * drm_prime_pages_to_sg
  *
  * this helper creates an sg table object from a set of pages
  * the driver is responsible for mapping the pages into the
  * importers address space
  */
 struct sg_table *drm_prime_pages_to_sg(struct page **pages, int nr_pages)
 {
 	struct sg_table *sg = NULL;
 	int ret;

 	sg = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
 	if (!sg) {
 		ret = -ENOMEM;
 		goto out;
 	}

 	ret = sg_alloc_table_from_pages(sg, pages, nr_pages, 0,
 				nr_pages << PAGE_SHIFT, GFP_KERNEL);
 	if (ret)
 		goto out;

 	return sg;
 out:
 	kfree(sg);
 	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL(drm_prime_pages_to_sg);

 /* export an sg table into an array of pages and addresses
    this is currently required by the TTM driver in order to do correct fault
    handling */
 int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
 				     dma_addr_t *addrs, int max_pages)
 {
 	unsigned count;
 	struct scatterlist *sg;
 	struct page *page;
 	u32 len, offset;
 	int pg_index;
 	dma_addr_t addr;

 	pg_index = 0;
 	for_each_sg(sgt->sgl, sg, sgt->nents, count) {
 		len = sg->length;
 		offset = sg->offset;
 		page = sg_page(sg);
 		addr = sg_dma_address(sg);

 		while (len > 0) {
 			if (WARN_ON(pg_index >= max_pages))
 				return -1;
 			pages[pg_index] = page;
 			if (addrs)
 				addrs[pg_index] = addr;

 			page++;
 			addr += PAGE_SIZE;
 			len -= PAGE_SIZE;
 			pg_index++;
 		}
 	}
 	return 0;
 }
 EXPORT_SYMBOL(drm_prime_sg_to_page_addr_arrays);
 /* helper function to cleanup a GEM/prime object */
 void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *sg)
 {
 	struct dma_buf_attachment *attach;
 	struct dma_buf *dma_buf;
 	attach = obj->import_attach;
 	if (sg)
 		dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
 	dma_buf = attach->dmabuf;
 	dma_buf_detach(attach->dmabuf, attach);
 	/* remove the reference */
 	dma_buf_put(dma_buf);
 }
 EXPORT_SYMBOL(drm_prime_gem_destroy);

 void drm_prime_init_file_private(struct drm_prime_file_private *prime_fpriv)
 {
 	INIT_LIST_HEAD(&prime_fpriv->head);
 	mutex_init(&prime_fpriv->lock);
 }
 EXPORT_SYMBOL(drm_prime_init_file_private);

 void drm_prime_destroy_file_private(struct drm_prime_file_private *prime_fpriv)
 {
 	/* by now drm_gem_release should've made sure the list is empty */
 	WARN_ON(!list_empty(&prime_fpriv->head));
 }
 EXPORT_SYMBOL(drm_prime_destroy_file_private);

 int drm_prime_lookup_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t *handle)
 {
 	struct drm_prime_member *member;

 	list_for_each_entry(member, &prime_fpriv->head, entry) {
 		if (member->dma_buf == dma_buf) {
 			*handle = member->handle;
 			return 0;
 		}
 	}
 	return -ENOENT;
 }
 EXPORT_SYMBOL(drm_prime_lookup_buf_handle);

 void drm_prime_remove_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf)
 {
 	struct drm_prime_member *member, *safe;

 	mutex_lock(&prime_fpriv->lock);
 	list_for_each_entry_safe(member, safe, &prime_fpriv->head, entry) {
 		if (member->dma_buf == dma_buf) {
 			dma_buf_put(dma_buf);
 			list_del(&member->entry);
 			kfree(member);
 		}
 	}
 	mutex_unlock(&prime_fpriv->lock);
 }
 EXPORT_SYMBOL(drm_prime_remove_buf_handle);
	/*
	* Copyright © 2012 Red Hat
	*
	* 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
	* THE AUTHORS OR COPYRIGHT HOLDERS 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.
	*
	* Authors:
	* Dave Airlie <airlied@redhat.com>
	* Rob Clark <rob.clark@linaro.org>
	*
	*/

	#include <linux/export.h>
	#include <linux/dma-buf.h>
	#include <drm/drmP.h>

	/*
	* DMA-BUF/GEM Object references and lifetime overview:
	*
	* On the export the dma_buf holds a reference to the exporting GEM
	* object. It takes this reference in handle_to_fd_ioctl, when it
	* first calls .prime_export and stores the exporting GEM object in
	* the dma_buf priv. This reference is released when the dma_buf
	* object goes away in the driver .release function.
	*
	* On the import the importing GEM object holds a reference to the
	* dma_buf (which in turn holds a ref to the exporting GEM object).
	* It takes that reference in the fd_to_handle ioctl.
	* It calls dma_buf_get, creates an attachment to it and stores the
	* attachment in the GEM object. When this attachment is destroyed
	* when the imported object is destroyed, we remove the attachment
	* and drop the reference to the dma_buf.
	*
	* Thus the chain of references always flows in one direction
	* (avoiding loops): importing_gem -> dmabuf -> exporting_gem
	*
	* Self-importing: if userspace is using PRIME as a replacement for flink
	* then it will get a fd->handle request for a GEM object that it created.
	* Drivers should detect this situation and return back the gem object
	* from the dma-buf private. Prime will do this automatically for drivers that
	* use the drm_gem_prime_{import,export} helpers.
	*/

	struct drm_prime_member {
	struct list_head entry;
	struct dma_buf *dma_buf;
	uint32_t handle;
	};

	struct drm_prime_attachment {
	struct sg_table *sgt;
	enum dma_data_direction dir;
	};

	static int drm_prime_add_buf_handle(struct drm_prime_file_private prime_fpriv, struct dma_buf dma_buf, uint32_t handle)
	{
	struct drm_prime_member *member;

	member = kmalloc(sizeof(*member), GFP_KERNEL);
	if (!member)
	return -ENOMEM;

	get_dma_buf(dma_buf);
	member->dma_buf = dma_buf;
	member->handle = handle;
	list_add(&member->entry, &prime_fpriv->head);
	return 0;
	}

	static int drm_gem_map_attach(struct dma_buf *dma_buf,
	struct device *target_dev,
	struct dma_buf_attachment *attach)
	{
	struct drm_prime_attachment *prime_attach;
	struct drm_gem_object *obj = dma_buf->priv;
	struct drm_device *dev = obj->dev;

	prime_attach = kzalloc(sizeof(*prime_attach), GFP_KERNEL);
	if (!prime_attach)
	return -ENOMEM;

	prime_attach->dir = DMA_NONE;
	attach->priv = prime_attach;

	if (!dev->driver->gem_prime_pin)
	return 0;

	return dev->driver->gem_prime_pin(obj);
	}

	static void drm_gem_map_detach(struct dma_buf *dma_buf,
	struct dma_buf_attachment *attach)
	{
	struct drm_prime_attachment *prime_attach = attach->priv;
	struct drm_gem_object *obj = dma_buf->priv;
	struct drm_device *dev = obj->dev;
	struct sg_table *sgt;

	if (dev->driver->gem_prime_unpin)
	dev->driver->gem_prime_unpin(obj);

	if (!prime_attach)
	return;

	sgt = prime_attach->sgt;

	if (prime_attach->dir != DMA_NONE)
	dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents,
	prime_attach->dir);

	sg_free_table(sgt);
	kfree(sgt);
	kfree(prime_attach);
	attach->priv = NULL;
	}

	static struct sg_table drm_gem_map_dma_buf(struct dma_buf_attachment attach,
	enum dma_data_direction dir)
	{
	struct drm_prime_attachment *prime_attach = attach->priv;
	struct drm_gem_object *obj = attach->dmabuf->priv;
	struct sg_table *sgt;

	if (WARN_ON(dir == DMA_NONE \|\| !prime_attach))
	return ERR_PTR(-EINVAL);

	/* return the cached mapping when possible */
	if (prime_attach->dir == dir)
	return prime_attach->sgt;

	/*
	* two mappings with different directions for the same attachment are
	* not allowed
	*/
	if (WARN_ON(prime_attach->dir != DMA_NONE))
	return ERR_PTR(-EBUSY);

	mutex_lock(&obj->dev->struct_mutex);

	sgt = obj->dev->driver->gem_prime_get_sg_table(obj);

	if (!IS_ERR(sgt)) {
	if (!dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir)) {
	sg_free_table(sgt);
	kfree(sgt);
	sgt = ERR_PTR(-ENOMEM);
	} else {
	prime_attach->sgt = sgt;
	prime_attach->dir = dir;
	}
	}

	mutex_unlock(&obj->dev->struct_mutex);
	return sgt;
	}

	static void drm_gem_unmap_dma_buf(struct dma_buf_attachment *attach,
	struct sg_table *sgt, enum dma_data_direction dir)
	{
	/* nothing to be done here */
	}

	static void drm_gem_dmabuf_release(struct dma_buf *dma_buf)
	{
	struct drm_gem_object *obj = dma_buf->priv;

	if (obj->export_dma_buf == dma_buf) {
	/* drop the reference on the export fd holds */
	obj->export_dma_buf = NULL;
	drm_gem_object_unreference_unlocked(obj);
	}
	}

	static void drm_gem_dmabuf_vmap(struct dma_buf dma_buf)
	{
	struct drm_gem_object *obj = dma_buf->priv;
	struct drm_device *dev = obj->dev;

	return dev->driver->gem_prime_vmap(obj);
	}

	static void drm_gem_dmabuf_vunmap(struct dma_buf dma_buf, void vaddr)
	{
	struct drm_gem_object *obj = dma_buf->priv;
	struct drm_device *dev = obj->dev;

	dev->driver->gem_prime_vunmap(obj, vaddr);
	}

	static void drm_gem_dmabuf_kmap_atomic(struct dma_buf dma_buf,
	unsigned long page_num)
	{
	return NULL;
	}

	static void drm_gem_dmabuf_kunmap_atomic(struct dma_buf *dma_buf,
	unsigned long page_num, void *addr)
	{

	}
	static void drm_gem_dmabuf_kmap(struct dma_buf dma_buf,
	unsigned long page_num)
	{
	return NULL;
	}

	static void drm_gem_dmabuf_kunmap(struct dma_buf *dma_buf,
	unsigned long page_num, void *addr)
	{

	}

	static int drm_gem_dmabuf_mmap(struct dma_buf *dma_buf,
	struct vm_area_struct *vma)
	{
	return -EINVAL;
	}

	static const struct dma_buf_ops drm_gem_prime_dmabuf_ops = {
	.attach = drm_gem_map_attach,
	.detach = drm_gem_map_detach,
	.map_dma_buf = drm_gem_map_dma_buf,
	.unmap_dma_buf = drm_gem_unmap_dma_buf,
	.release = drm_gem_dmabuf_release,
	.kmap = drm_gem_dmabuf_kmap,
	.kmap_atomic = drm_gem_dmabuf_kmap_atomic,
	.kunmap = drm_gem_dmabuf_kunmap,
	.kunmap_atomic = drm_gem_dmabuf_kunmap_atomic,
	.mmap = drm_gem_dmabuf_mmap,
	.vmap = drm_gem_dmabuf_vmap,
	.vunmap = drm_gem_dmabuf_vunmap,
	};

	/**
	* DOC: PRIME Helpers
	*
	* Drivers can implement @gem_prime_export and @gem_prime_import in terms of
	* simpler APIs by using the helper functions @drm_gem_prime_export and
	* @drm_gem_prime_import. These functions implement dma-buf support in terms of
	* five lower-level driver callbacks:
	*
	* Export callbacks:
	*
	* - @gem_prime_pin (optional): prepare a GEM object for exporting
	*
	* - @gem_prime_get_sg_table: provide a scatter/gather table of pinned pages
	*
	* - @gem_prime_vmap: vmap a buffer exported by your driver
	*
	* - @gem_prime_vunmap: vunmap a buffer exported by your driver
	*
	* Import callback:
	*
	* - @gem_prime_import_sg_table (import): produce a GEM object from another
	* driver's scatter/gather table
	*/

	struct dma_buf drm_gem_prime_export(struct drm_device dev,
	struct drm_gem_object *obj, int flags)
	{
	return dma_buf_export(obj, &drm_gem_prime_dmabuf_ops, obj->size, flags);
	}
	EXPORT_SYMBOL(drm_gem_prime_export);

	int drm_gem_prime_handle_to_fd(struct drm_device *dev,
	struct drm_file *file_priv, uint32_t handle, uint32_t flags,
	int *prime_fd)
	{
	struct drm_gem_object *obj;
	void *buf;
	int ret = 0;
	struct dma_buf *dmabuf;

	obj = drm_gem_object_lookup(dev, file_priv, handle);
	if (!obj)
	return -ENOENT;

	mutex_lock(&file_priv->prime.lock);
	/* re-export the original imported object */
	if (obj->import_attach) {
	dmabuf = obj->import_attach->dmabuf;
	goto out_have_obj;
	}

	if (obj->export_dma_buf) {
	dmabuf = obj->export_dma_buf;
	goto out_have_obj;
	}

	buf = dev->driver->gem_prime_export(dev, obj, flags);
	if (IS_ERR(buf)) {
	/* normally the created dma-buf takes ownership of the ref,
	* but if that fails then drop the ref
	*/
	ret = PTR_ERR(buf);
	goto out;
	}
	obj->export_dma_buf = buf;

	/* if we've exported this buffer the cheat and add it to the import list
	* so we get the correct handle back
	*/
	ret = drm_prime_add_buf_handle(&file_priv->prime,
	obj->export_dma_buf, handle);
	if (ret)
	goto fail_put_dmabuf;

	*prime_fd = dma_buf_fd(buf, flags);
	mutex_unlock(&file_priv->prime.lock);
	return 0;

	out_have_obj:
	get_dma_buf(dmabuf);
	*prime_fd = dma_buf_fd(dmabuf, flags);
	goto out;

	fail_put_dmabuf:
	/* clear NOT to be checked when releasing dma_buf */
	obj->export_dma_buf = NULL;
	dma_buf_put(buf);
	out:
	drm_gem_object_unreference_unlocked(obj);
	mutex_unlock(&file_priv->prime.lock);
	return ret;
	}
	EXPORT_SYMBOL(drm_gem_prime_handle_to_fd);

	struct drm_gem_object drm_gem_prime_import(struct drm_device dev,
	struct dma_buf *dma_buf)
	{
	struct dma_buf_attachment *attach;
	struct sg_table *sgt;
	struct drm_gem_object *obj;
	int ret;

	if (!dev->driver->gem_prime_import_sg_table)
	return ERR_PTR(-EINVAL);

	if (dma_buf->ops == &drm_gem_prime_dmabuf_ops) {
	obj = dma_buf->priv;
	if (obj->dev == dev) {
	/*
	* Importing dmabuf exported from out own gem increases
	* refcount on gem itself instead of f_count of dmabuf.
	*/
	drm_gem_object_reference(obj);
	return obj;
	}
	}

	attach = dma_buf_attach(dma_buf, dev->dev);
	if (IS_ERR(attach))
	return ERR_CAST(attach);

	get_dma_buf(dma_buf);

	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
	if (IS_ERR_OR_NULL(sgt)) {
	ret = PTR_ERR(sgt);
	goto fail_detach;
	}

	obj = dev->driver->gem_prime_import_sg_table(dev, dma_buf->size, sgt);
	if (IS_ERR(obj)) {
	ret = PTR_ERR(obj);
	goto fail_unmap;
	}

	obj->import_attach = attach;

	return obj;

	fail_unmap:
	dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
	fail_detach:
	dma_buf_detach(dma_buf, attach);
	dma_buf_put(dma_buf);

	return ERR_PTR(ret);
	}
	EXPORT_SYMBOL(drm_gem_prime_import);

	int drm_gem_prime_fd_to_handle(struct drm_device *dev,
	struct drm_file file_priv, int prime_fd, uint32_t handle)
	{
	struct dma_buf *dma_buf;
	struct drm_gem_object *obj;
	int ret;

	dma_buf = dma_buf_get(prime_fd);
	if (IS_ERR(dma_buf))
	return PTR_ERR(dma_buf);

	mutex_lock(&file_priv->prime.lock);

	ret = drm_prime_lookup_buf_handle(&file_priv->prime,
	dma_buf, handle);
	if (!ret) {
	ret = 0;
	goto out_put;
	}

	/* never seen this one, need to import */
	obj = dev->driver->gem_prime_import(dev, dma_buf);
	if (IS_ERR(obj)) {
	ret = PTR_ERR(obj);
	goto out_put;
	}

	ret = drm_gem_handle_create(file_priv, obj, handle);
	drm_gem_object_unreference_unlocked(obj);
	if (ret)
	goto out_put;

	ret = drm_prime_add_buf_handle(&file_priv->prime,
	dma_buf, *handle);
	if (ret)
	goto fail;

	mutex_unlock(&file_priv->prime.lock);

	dma_buf_put(dma_buf);

	return 0;

	fail:
	/* hmm, if driver attached, we are relying on the free-object path
	* to detach.. which seems ok..
	*/
	drm_gem_object_handle_unreference_unlocked(obj);
	out_put:
	dma_buf_put(dma_buf);
	mutex_unlock(&file_priv->prime.lock);
	return ret;
	}
	EXPORT_SYMBOL(drm_gem_prime_fd_to_handle);

	int drm_prime_handle_to_fd_ioctl(struct drm_device dev, void data,
	struct drm_file *file_priv)
	{
	struct drm_prime_handle *args = data;
	uint32_t flags;

	if (!drm_core_check_feature(dev, DRIVER_PRIME))
	return -EINVAL;

	if (!dev->driver->prime_handle_to_fd)
	return -ENOSYS;

	/* check flags are valid */
	if (args->flags & ~DRM_CLOEXEC)
	return -EINVAL;

	/* we only want to pass DRM_CLOEXEC which is == O_CLOEXEC */
	flags = args->flags & DRM_CLOEXEC;

	return dev->driver->prime_handle_to_fd(dev, file_priv,
	args->handle, flags, &args->fd);
	}

	int drm_prime_fd_to_handle_ioctl(struct drm_device dev, void data,
	struct drm_file *file_priv)
	{
	struct drm_prime_handle *args = data;

	if (!drm_core_check_feature(dev, DRIVER_PRIME))
	return -EINVAL;

	if (!dev->driver->prime_fd_to_handle)
	return -ENOSYS;

	return dev->driver->prime_fd_to_handle(dev, file_priv,
	args->fd, &args->handle);
	}

	/*
	* drm_prime_pages_to_sg
	*
	* this helper creates an sg table object from a set of pages
	* the driver is responsible for mapping the pages into the
	* importers address space
	*/
	struct sg_table drm_prime_pages_to_sg(struct page *pages, int nr_pages)
	{
	struct sg_table *sg = NULL;
	int ret;

	sg = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
	if (!sg) {
	ret = -ENOMEM;
	goto out;
	}

	ret = sg_alloc_table_from_pages(sg, pages, nr_pages, 0,
	nr_pages << PAGE_SHIFT, GFP_KERNEL);
	if (ret)
	goto out;

	return sg;
	out:
	kfree(sg);
	return ERR_PTR(ret);
	}
	EXPORT_SYMBOL(drm_prime_pages_to_sg);

	/* export an sg table into an array of pages and addresses
	this is currently required by the TTM driver in order to do correct fault
	handling */
	int drm_prime_sg_to_page_addr_arrays(struct sg_table sgt, struct page *pages,
	dma_addr_t *addrs, int max_pages)
	{
	unsigned count;
	struct scatterlist *sg;
	struct page *page;
	u32 len, offset;
	int pg_index;
	dma_addr_t addr;

	pg_index = 0;
	for_each_sg(sgt->sgl, sg, sgt->nents, count) {
	len = sg->length;
	offset = sg->offset;
	page = sg_page(sg);
	addr = sg_dma_address(sg);

	while (len > 0) {
	if (WARN_ON(pg_index >= max_pages))
	return -1;
	pages[pg_index] = page;
	if (addrs)
	addrs[pg_index] = addr;

	page++;
	addr += PAGE_SIZE;
	len -= PAGE_SIZE;
	pg_index++;
	}
	}
	return 0;
	}
	EXPORT_SYMBOL(drm_prime_sg_to_page_addr_arrays);
	/* helper function to cleanup a GEM/prime object */
	void drm_prime_gem_destroy(struct drm_gem_object obj, struct sg_table sg)
	{
	struct dma_buf_attachment *attach;
	struct dma_buf *dma_buf;
	attach = obj->import_attach;
	if (sg)
	dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
	dma_buf = attach->dmabuf;
	dma_buf_detach(attach->dmabuf, attach);
	/* remove the reference */
	dma_buf_put(dma_buf);
	}
	EXPORT_SYMBOL(drm_prime_gem_destroy);

	void drm_prime_init_file_private(struct drm_prime_file_private *prime_fpriv)
	{
	INIT_LIST_HEAD(&prime_fpriv->head);
	mutex_init(&prime_fpriv->lock);
	}
	EXPORT_SYMBOL(drm_prime_init_file_private);

	void drm_prime_destroy_file_private(struct drm_prime_file_private *prime_fpriv)
	{
	/* by now drm_gem_release should've made sure the list is empty */
	WARN_ON(!list_empty(&prime_fpriv->head));
	}
	EXPORT_SYMBOL(drm_prime_destroy_file_private);

	int drm_prime_lookup_buf_handle(struct drm_prime_file_private prime_fpriv, struct dma_buf dma_buf, uint32_t *handle)
	{
	struct drm_prime_member *member;

	list_for_each_entry(member, &prime_fpriv->head, entry) {
	if (member->dma_buf == dma_buf) {
	*handle = member->handle;
	return 0;
	}
	}
	return -ENOENT;
	}
	EXPORT_SYMBOL(drm_prime_lookup_buf_handle);

	void drm_prime_remove_buf_handle(struct drm_prime_file_private prime_fpriv, struct dma_buf dma_buf)
	{
	struct drm_prime_member member, safe;

	mutex_lock(&prime_fpriv->lock);
	list_for_each_entry_safe(member, safe, &prime_fpriv->head, entry) {
	if (member->dma_buf == dma_buf) {
	dma_buf_put(dma_buf);
	list_del(&member->entry);
	kfree(member);
	}
	}
	mutex_unlock(&prime_fpriv->lock);
	}
	EXPORT_SYMBOL(drm_prime_remove_buf_handle);