drivers/dma-buf/sync_file.c - kernel/msm-4.19 - Gitiles

 /*
  * drivers/dma-buf/sync_file.c
  *
  * Copyright (C) 2012 Google, Inc.
  *
  * This software is licensed under the terms of the GNU General Public
  * License version 2, as published by the Free Software Foundation, and
  * may be copied, distributed, and modified under those terms.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  */

 #include <linux/export.h>
 #include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/kernel.h>
 #include <linux/poll.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/anon_inodes.h>
 #include <linux/sync_file.h>
 #include <uapi/linux/sync_file.h>

 static const struct file_operations sync_file_fops;

 static struct sync_file *sync_file_alloc(void)
 {
 	struct sync_file *sync_file;

 	sync_file = kzalloc(sizeof(*sync_file), GFP_KERNEL);
 	if (!sync_file)
 		return NULL;

 	sync_file->file = anon_inode_getfile("sync_file", &sync_file_fops,
 					     sync_file, 0);
 	if (IS_ERR(sync_file->file))
 		goto err;

 	init_waitqueue_head(&sync_file->wq);

 	INIT_LIST_HEAD(&sync_file->cb.node);

 	return sync_file;

 err:
 	kfree(sync_file);
 	return NULL;
 }

 static void fence_check_cb_func(struct dma_fence *f, struct dma_fence_cb *cb)
 {
 	struct sync_file *sync_file;

 	sync_file = container_of(cb, struct sync_file, cb);

 	wake_up_all(&sync_file->wq);
 }

 /**
  * sync_file_create() - creates a sync file
  * @fence:	fence to add to the sync_fence
  *
  * Creates a sync_file containg @fence. This function acquires and additional
  * reference of @fence for the newly-created &sync_file, if it succeeds. The
  * sync_file can be released with fput(sync_file->file). Returns the
  * sync_file or NULL in case of error.
  */
 struct sync_file *sync_file_create(struct dma_fence *fence)
 {
 	struct sync_file *sync_file;

 	sync_file = sync_file_alloc();
 	if (!sync_file)
 		return NULL;

 	sync_file->fence = dma_fence_get(fence);

 	return sync_file;
 }
 EXPORT_SYMBOL(sync_file_create);

 static struct sync_file *sync_file_fdget(int fd)
 {
 	struct file *file = fget(fd);

 	if (!file)
 		return NULL;

 	if (file->f_op != &sync_file_fops)
 		goto err;

 	return file->private_data;

 err:
 	fput(file);
 	return NULL;
 }

 /**
  * sync_file_get_fence - get the fence related to the sync_file fd
  * @fd:		sync_file fd to get the fence from
  *
  * Ensures @fd references a valid sync_file and returns a fence that
  * represents all fence in the sync_file. On error NULL is returned.
  */
 struct dma_fence *sync_file_get_fence(int fd)
 {
 	struct sync_file *sync_file;
 	struct dma_fence *fence;

 	sync_file = sync_file_fdget(fd);
 	if (!sync_file)
 		return NULL;

 	fence = dma_fence_get(sync_file->fence);
 	fput(sync_file->file);

 	return fence;
 }
 EXPORT_SYMBOL(sync_file_get_fence);

 /**
  * sync_file_get_name - get the name of the sync_file
  * @sync_file:		sync_file to get the fence from
  * @buf:		destination buffer to copy sync_file name into
  * @len:		available size of destination buffer.
  *
  * Each sync_file may have a name assigned either by the user (when merging
  * sync_files together) or created from the fence it contains. In the latter
  * case construction of the name is deferred until use, and so requires
  * sync_file_get_name().
  *
  * Returns: a string representing the name.
  */
 char *sync_file_get_name(struct sync_file *sync_file, char *buf, int len)
 {
 	if (sync_file->user_name[0]) {
 		strlcpy(buf, sync_file->user_name, len);
 	} else {
 		struct dma_fence *fence = sync_file->fence;

 		snprintf(buf, len, "%s-%s%llu-%d",
 			 fence->ops->get_driver_name(fence),
 			 fence->ops->get_timeline_name(fence),
 			 fence->context,
 			 fence->seqno);
 	}

 	return buf;
 }

 static int sync_file_set_fence(struct sync_file *sync_file,
 			       struct dma_fence **fences, int num_fences)
 {
 	struct dma_fence_array *array;

 	/*
 	 * The reference for the fences in the new sync_file and held
 	 * in add_fence() during the merge procedure, so for num_fences == 1
 	 * we already own a new reference to the fence. For num_fence > 1
 	 * we own the reference of the dma_fence_array creation.
 	 */
 	if (num_fences == 1) {
 		sync_file->fence = fences[0];
 		kfree(fences);
 	} else {
 		array = dma_fence_array_create(num_fences, fences,
 					       dma_fence_context_alloc(1),
 					       1, false);
 		if (!array)
 			return -ENOMEM;

 		sync_file->fence = &array->base;
 	}

 	return 0;
 }

 static struct dma_fence **get_fences(struct sync_file *sync_file,
 				     int *num_fences)
 {
 	if (dma_fence_is_array(sync_file->fence)) {
 		struct dma_fence_array *array = to_dma_fence_array(sync_file->fence);

 		*num_fences = array->num_fences;
 		return array->fences;
 	}

 	*num_fences = 1;
 	return &sync_file->fence;
 }

 static void add_fence(struct dma_fence **fences,
 		      int *i, struct dma_fence *fence)
 {
 	fences[*i] = fence;

 	if (!dma_fence_is_signaled(fence)) {
 		dma_fence_get(fence);
 		(*i)++;
 	}
 }

 /**
  * sync_file_merge() - merge two sync_files
  * @name:	name of new fence
  * @a:		sync_file a
  * @b:		sync_file b
  *
  * Creates a new sync_file which contains copies of all the fences in both
  * @a and @b.  @a and @b remain valid, independent sync_file. Returns the
  * new merged sync_file or NULL in case of error.
  */
 static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
 					 struct sync_file *b)
 {
 	struct sync_file *sync_file;
 	struct dma_fence **fences, **nfences, **a_fences, **b_fences;
 	int i, i_a, i_b, num_fences, a_num_fences, b_num_fences;

 	sync_file = sync_file_alloc();
 	if (!sync_file)
 		return NULL;

 	a_fences = get_fences(a, &a_num_fences);
 	b_fences = get_fences(b, &b_num_fences);
 	if (a_num_fences > INT_MAX - b_num_fences)
 		return NULL;

 	num_fences = a_num_fences + b_num_fences;

 	fences = kcalloc(num_fences, sizeof(*fences), GFP_KERNEL);
 	if (!fences)
 		goto err;

 	/*
 	 * Assume sync_file a and b are both ordered and have no
 	 * duplicates with the same context.
 	 *
 	 * If a sync_file can only be created with sync_file_merge
 	 * and sync_file_create, this is a reasonable assumption.
 	 */
 	for (i = i_a = i_b = 0; i_a < a_num_fences && i_b < b_num_fences; ) {
 		struct dma_fence *pt_a = a_fences[i_a];
 		struct dma_fence *pt_b = b_fences[i_b];

 		if (pt_a->context < pt_b->context) {
 			add_fence(fences, &i, pt_a);

 			i_a++;
 		} else if (pt_a->context > pt_b->context) {
 			add_fence(fences, &i, pt_b);

 			i_b++;
 		} else {
 			if (pt_a->seqno - pt_b->seqno <= INT_MAX)
 				add_fence(fences, &i, pt_a);
 			else
 				add_fence(fences, &i, pt_b);

 			i_a++;
 			i_b++;
 		}
 	}

 	for (; i_a < a_num_fences; i_a++)
 		add_fence(fences, &i, a_fences[i_a]);

 	for (; i_b < b_num_fences; i_b++)
 		add_fence(fences, &i, b_fences[i_b]);

 	if (i == 0)
 		fences[i++] = dma_fence_get(a_fences[0]);

 	if (num_fences > i) {
 		nfences = krealloc(fences, i * sizeof(*fences),
 				  GFP_KERNEL);
 		if (!nfences)
 			goto err;

 		fences = nfences;
 	}

 	if (sync_file_set_fence(sync_file, fences, i) < 0) {
 		kfree(fences);
 		goto err;
 	}

 	strlcpy(sync_file->user_name, name, sizeof(sync_file->user_name));
 	return sync_file;

 err:
 	fput(sync_file->file);
 	return NULL;

 }

 static int sync_file_release(struct inode *inode, struct file *file)
 {
 	struct sync_file *sync_file = file->private_data;

 	if (test_bit(POLL_ENABLED, &sync_file->fence->flags))
 		dma_fence_remove_callback(sync_file->fence, &sync_file->cb);
 	dma_fence_put(sync_file->fence);
 	kfree(sync_file);

 	return 0;
 }

 static unsigned int sync_file_poll(struct file *file, poll_table *wait)
 {
 	struct sync_file *sync_file = file->private_data;

 	poll_wait(file, &sync_file->wq, wait);

 	if (!test_and_set_bit(POLL_ENABLED, &sync_file->fence->flags)) {
 		if (dma_fence_add_callback(sync_file->fence, &sync_file->cb,
 					   fence_check_cb_func) < 0)
 			wake_up_all(&sync_file->wq);
 	}

 	return dma_fence_is_signaled(sync_file->fence) ? POLLIN : 0;
 }

 static long sync_file_ioctl_merge(struct sync_file *sync_file,
 				  unsigned long arg)
 {
 	int fd = get_unused_fd_flags(O_CLOEXEC);
 	int err;
 	struct sync_file *fence2, *fence3;
 	struct sync_merge_data data;

 	if (fd < 0)
 		return fd;

 	if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
 		err = -EFAULT;
 		goto err_put_fd;
 	}

 	if (data.flags || data.pad) {
 		err = -EINVAL;
 		goto err_put_fd;
 	}

 	fence2 = sync_file_fdget(data.fd2);
 	if (!fence2) {
 		err = -ENOENT;
 		goto err_put_fd;
 	}

 	data.name[sizeof(data.name) - 1] = '\0';
 	fence3 = sync_file_merge(data.name, sync_file, fence2);
 	if (!fence3) {
 		err = -ENOMEM;
 		goto err_put_fence2;
 	}

 	data.fence = fd;
 	if (copy_to_user((void __user *)arg, &data, sizeof(data))) {
 		err = -EFAULT;
 		goto err_put_fence3;
 	}

 	fd_install(fd, fence3->file);
 	fput(fence2->file);
 	return 0;

 err_put_fence3:
 	fput(fence3->file);

 err_put_fence2:
 	fput(fence2->file);

 err_put_fd:
 	put_unused_fd(fd);
 	return err;
 }

 static void sync_fill_fence_info(struct dma_fence *fence,
 				 struct sync_fence_info *info)
 {
 	strlcpy(info->obj_name, fence->ops->get_timeline_name(fence),
 		sizeof(info->obj_name));
 	strlcpy(info->driver_name, fence->ops->get_driver_name(fence),
 		sizeof(info->driver_name));

 	info->status = dma_fence_get_status(fence);
 	info->timestamp_ns = ktime_to_ns(fence->timestamp);
 }

 static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
 				       unsigned long arg)
 {
 	struct sync_file_info info;
 	struct sync_fence_info *fence_info = NULL;
 	struct dma_fence **fences;
 	__u32 size;
 	int num_fences, ret, i;

 	if (copy_from_user(&info, (void __user *)arg, sizeof(info)))
 		return -EFAULT;

 	if (info.flags || info.pad)
 		return -EINVAL;

 	fences = get_fences(sync_file, &num_fences);

 	/*
 	 * Passing num_fences = 0 means that userspace doesn't want to
 	 * retrieve any sync_fence_info. If num_fences = 0 we skip filling
 	 * sync_fence_info and return the actual number of fences on
 	 * info->num_fences.
 	 */
 	if (!info.num_fences)
 		goto no_fences;

 	if (info.num_fences < num_fences)
 		return -EINVAL;

 	size = num_fences * sizeof(*fence_info);
 	fence_info = kzalloc(size, GFP_KERNEL);
 	if (!fence_info)
 		return -ENOMEM;

 	for (i = 0; i < num_fences; i++)
 		sync_fill_fence_info(fences[i], &fence_info[i]);

 	if (copy_to_user(u64_to_user_ptr(info.sync_fence_info), fence_info,
 			 size)) {
 		ret = -EFAULT;
 		goto out;
 	}

 no_fences:
 	sync_file_get_name(sync_file, info.name, sizeof(info.name));
 	info.status = dma_fence_is_signaled(sync_file->fence);
 	info.num_fences = num_fences;

 	if (copy_to_user((void __user *)arg, &info, sizeof(info)))
 		ret = -EFAULT;
 	else
 		ret = 0;

 out:
 	kfree(fence_info);

 	return ret;
 }

 static long sync_file_ioctl(struct file *file, unsigned int cmd,
 			    unsigned long arg)
 {
 	struct sync_file *sync_file = file->private_data;

 	switch (cmd) {
 	case SYNC_IOC_MERGE:
 		return sync_file_ioctl_merge(sync_file, arg);

 	case SYNC_IOC_FILE_INFO:
 		return sync_file_ioctl_fence_info(sync_file, arg);

 	default:
 		return -ENOTTY;
 	}
 }

 static const struct file_operations sync_file_fops = {
 	.release = sync_file_release,
 	.poll = sync_file_poll,
 	.unlocked_ioctl = sync_file_ioctl,
 	.compat_ioctl = sync_file_ioctl,
 };
	/*
	* drivers/dma-buf/sync_file.c
	*
	* Copyright (C) 2012 Google, Inc.
	*
	* This software is licensed under the terms of the GNU General Public
	* License version 2, as published by the Free Software Foundation, and
	* may be copied, distributed, and modified under those terms.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	*/

	#include <linux/export.h>
	#include <linux/file.h>
	#include <linux/fs.h>
	#include <linux/kernel.h>
	#include <linux/poll.h>
	#include <linux/sched.h>
	#include <linux/slab.h>
	#include <linux/uaccess.h>
	#include <linux/anon_inodes.h>
	#include <linux/sync_file.h>
	#include <uapi/linux/sync_file.h>

	static const struct file_operations sync_file_fops;

	static struct sync_file *sync_file_alloc(void)
	{
	struct sync_file *sync_file;

	sync_file = kzalloc(sizeof(*sync_file), GFP_KERNEL);
	if (!sync_file)
	return NULL;

	sync_file->file = anon_inode_getfile("sync_file", &sync_file_fops,
	sync_file, 0);
	if (IS_ERR(sync_file->file))
	goto err;

	init_waitqueue_head(&sync_file->wq);

	INIT_LIST_HEAD(&sync_file->cb.node);

	return sync_file;

	err:
	kfree(sync_file);
	return NULL;
	}

	static void fence_check_cb_func(struct dma_fence f, struct dma_fence_cb cb)
	{
	struct sync_file *sync_file;

	sync_file = container_of(cb, struct sync_file, cb);

	wake_up_all(&sync_file->wq);
	}

	/**
	* sync_file_create() - creates a sync file
	* @fence: fence to add to the sync_fence
	*
	* Creates a sync_file containg @fence. This function acquires and additional
	* reference of @fence for the newly-created &sync_file, if it succeeds. The
	* sync_file can be released with fput(sync_file->file). Returns the
	* sync_file or NULL in case of error.
	*/
	struct sync_file sync_file_create(struct dma_fence fence)
	{
	struct sync_file *sync_file;

	sync_file = sync_file_alloc();
	if (!sync_file)
	return NULL;

	sync_file->fence = dma_fence_get(fence);

	return sync_file;
	}
	EXPORT_SYMBOL(sync_file_create);

	static struct sync_file *sync_file_fdget(int fd)
	{
	struct file *file = fget(fd);

	if (!file)
	return NULL;

	if (file->f_op != &sync_file_fops)
	goto err;

	return file->private_data;

	err:
	fput(file);
	return NULL;
	}

	/**
	* sync_file_get_fence - get the fence related to the sync_file fd
	* @fd: sync_file fd to get the fence from
	*
	* Ensures @fd references a valid sync_file and returns a fence that
	* represents all fence in the sync_file. On error NULL is returned.
	*/
	struct dma_fence *sync_file_get_fence(int fd)
	{
	struct sync_file *sync_file;
	struct dma_fence *fence;

	sync_file = sync_file_fdget(fd);
	if (!sync_file)
	return NULL;

	fence = dma_fence_get(sync_file->fence);
	fput(sync_file->file);

	return fence;
	}
	EXPORT_SYMBOL(sync_file_get_fence);

	/**
	* sync_file_get_name - get the name of the sync_file
	* @sync_file: sync_file to get the fence from
	* @buf: destination buffer to copy sync_file name into
	* @len: available size of destination buffer.
	*
	* Each sync_file may have a name assigned either by the user (when merging
	* sync_files together) or created from the fence it contains. In the latter
	* case construction of the name is deferred until use, and so requires
	* sync_file_get_name().
	*
	* Returns: a string representing the name.
	*/
	char sync_file_get_name(struct sync_file sync_file, char *buf, int len)
	{
	if (sync_file->user_name[0]) {
	strlcpy(buf, sync_file->user_name, len);
	} else {
	struct dma_fence *fence = sync_file->fence;

	snprintf(buf, len, "%s-%s%llu-%d",
	fence->ops->get_driver_name(fence),
	fence->ops->get_timeline_name(fence),
	fence->context,
	fence->seqno);
	}

	return buf;
	}

	static int sync_file_set_fence(struct sync_file *sync_file,
	struct dma_fence **fences, int num_fences)
	{
	struct dma_fence_array *array;

	/*
	* The reference for the fences in the new sync_file and held
	* in add_fence() during the merge procedure, so for num_fences == 1
	* we already own a new reference to the fence. For num_fence > 1
	* we own the reference of the dma_fence_array creation.
	*/
	if (num_fences == 1) {
	sync_file->fence = fences[0];
	kfree(fences);
	} else {
	array = dma_fence_array_create(num_fences, fences,
	dma_fence_context_alloc(1),
	1, false);
	if (!array)
	return -ENOMEM;

	sync_file->fence = &array->base;
	}

	return 0;
	}

	static struct dma_fence *get_fences(struct sync_file sync_file,
	int *num_fences)
	{
	if (dma_fence_is_array(sync_file->fence)) {
	struct dma_fence_array *array = to_dma_fence_array(sync_file->fence);

	*num_fences = array->num_fences;
	return array->fences;
	}

	*num_fences = 1;
	return &sync_file->fence;
	}

	static void add_fence(struct dma_fence **fences,
	int i, struct dma_fence fence)
	{
	fences[*i] = fence;

	if (!dma_fence_is_signaled(fence)) {
	dma_fence_get(fence);
	(*i)++;
	}
	}

	/**
	* sync_file_merge() - merge two sync_files
	* @name: name of new fence
	* @a: sync_file a
	* @b: sync_file b
	*
	* Creates a new sync_file which contains copies of all the fences in both
	* @a and @b. @a and @b remain valid, independent sync_file. Returns the
	* new merged sync_file or NULL in case of error.
	*/
	static struct sync_file sync_file_merge(const char name, struct sync_file *a,
	struct sync_file *b)
	{
	struct sync_file *sync_file;
	struct dma_fence fences, nfences, a_fences, b_fences;
	int i, i_a, i_b, num_fences, a_num_fences, b_num_fences;

	sync_file = sync_file_alloc();
	if (!sync_file)
	return NULL;

	a_fences = get_fences(a, &a_num_fences);
	b_fences = get_fences(b, &b_num_fences);
	if (a_num_fences > INT_MAX - b_num_fences)
	return NULL;

	num_fences = a_num_fences + b_num_fences;

	fences = kcalloc(num_fences, sizeof(*fences), GFP_KERNEL);
	if (!fences)
	goto err;

	/*
	* Assume sync_file a and b are both ordered and have no
	* duplicates with the same context.
	*
	* If a sync_file can only be created with sync_file_merge
	* and sync_file_create, this is a reasonable assumption.
	*/
	for (i = i_a = i_b = 0; i_a < a_num_fences && i_b < b_num_fences; ) {
	struct dma_fence *pt_a = a_fences[i_a];
	struct dma_fence *pt_b = b_fences[i_b];

	if (pt_a->context < pt_b->context) {
	add_fence(fences, &i, pt_a);

	i_a++;
	} else if (pt_a->context > pt_b->context) {
	add_fence(fences, &i, pt_b);

	i_b++;
	} else {
	if (pt_a->seqno - pt_b->seqno <= INT_MAX)
	add_fence(fences, &i, pt_a);
	else
	add_fence(fences, &i, pt_b);

	i_a++;
	i_b++;
	}
	}

	for (; i_a < a_num_fences; i_a++)
	add_fence(fences, &i, a_fences[i_a]);

	for (; i_b < b_num_fences; i_b++)
	add_fence(fences, &i, b_fences[i_b]);

	if (i == 0)
	fences[i++] = dma_fence_get(a_fences[0]);

	if (num_fences > i) {
	nfences = krealloc(fences, i * sizeof(*fences),
	GFP_KERNEL);
	if (!nfences)
	goto err;

	fences = nfences;
	}

	if (sync_file_set_fence(sync_file, fences, i) < 0) {
	kfree(fences);
	goto err;
	}

	strlcpy(sync_file->user_name, name, sizeof(sync_file->user_name));
	return sync_file;

	err:
	fput(sync_file->file);
	return NULL;

	}

	static int sync_file_release(struct inode inode, struct file file)
	{
	struct sync_file *sync_file = file->private_data;

	if (test_bit(POLL_ENABLED, &sync_file->fence->flags))
	dma_fence_remove_callback(sync_file->fence, &sync_file->cb);
	dma_fence_put(sync_file->fence);
	kfree(sync_file);

	return 0;
	}

	static unsigned int sync_file_poll(struct file file, poll_table wait)
	{
	struct sync_file *sync_file = file->private_data;

	poll_wait(file, &sync_file->wq, wait);

	if (!test_and_set_bit(POLL_ENABLED, &sync_file->fence->flags)) {
	if (dma_fence_add_callback(sync_file->fence, &sync_file->cb,
	fence_check_cb_func) < 0)
	wake_up_all(&sync_file->wq);
	}

	return dma_fence_is_signaled(sync_file->fence) ? POLLIN : 0;
	}

	static long sync_file_ioctl_merge(struct sync_file *sync_file,
	unsigned long arg)
	{
	int fd = get_unused_fd_flags(O_CLOEXEC);
	int err;
	struct sync_file fence2, fence3;
	struct sync_merge_data data;

	if (fd < 0)
	return fd;

	if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
	err = -EFAULT;
	goto err_put_fd;
	}

	if (data.flags \|\| data.pad) {
	err = -EINVAL;
	goto err_put_fd;
	}

	fence2 = sync_file_fdget(data.fd2);
	if (!fence2) {
	err = -ENOENT;
	goto err_put_fd;
	}

	data.name[sizeof(data.name) - 1] = '\0';
	fence3 = sync_file_merge(data.name, sync_file, fence2);
	if (!fence3) {
	err = -ENOMEM;
	goto err_put_fence2;
	}

	data.fence = fd;
	if (copy_to_user((void __user *)arg, &data, sizeof(data))) {
	err = -EFAULT;
	goto err_put_fence3;
	}

	fd_install(fd, fence3->file);
	fput(fence2->file);
	return 0;

	err_put_fence3:
	fput(fence3->file);

	err_put_fence2:
	fput(fence2->file);

	err_put_fd:
	put_unused_fd(fd);
	return err;
	}

	static void sync_fill_fence_info(struct dma_fence *fence,
	struct sync_fence_info *info)
	{
	strlcpy(info->obj_name, fence->ops->get_timeline_name(fence),
	sizeof(info->obj_name));
	strlcpy(info->driver_name, fence->ops->get_driver_name(fence),
	sizeof(info->driver_name));

	info->status = dma_fence_get_status(fence);
	info->timestamp_ns = ktime_to_ns(fence->timestamp);
	}

	static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
	unsigned long arg)
	{
	struct sync_file_info info;
	struct sync_fence_info *fence_info = NULL;
	struct dma_fence **fences;
	__u32 size;
	int num_fences, ret, i;

	if (copy_from_user(&info, (void __user *)arg, sizeof(info)))
	return -EFAULT;

	if (info.flags \|\| info.pad)
	return -EINVAL;

	fences = get_fences(sync_file, &num_fences);

	/*
	* Passing num_fences = 0 means that userspace doesn't want to
	* retrieve any sync_fence_info. If num_fences = 0 we skip filling
	* sync_fence_info and return the actual number of fences on
	* info->num_fences.
	*/
	if (!info.num_fences)
	goto no_fences;

	if (info.num_fences < num_fences)
	return -EINVAL;

	size = num_fences * sizeof(*fence_info);
	fence_info = kzalloc(size, GFP_KERNEL);
	if (!fence_info)
	return -ENOMEM;

	for (i = 0; i < num_fences; i++)
	sync_fill_fence_info(fences[i], &fence_info[i]);

	if (copy_to_user(u64_to_user_ptr(info.sync_fence_info), fence_info,
	size)) {
	ret = -EFAULT;
	goto out;
	}

	no_fences:
	sync_file_get_name(sync_file, info.name, sizeof(info.name));
	info.status = dma_fence_is_signaled(sync_file->fence);
	info.num_fences = num_fences;

	if (copy_to_user((void __user *)arg, &info, sizeof(info)))
	ret = -EFAULT;
	else
	ret = 0;

	out:
	kfree(fence_info);

	return ret;
	}

	static long sync_file_ioctl(struct file *file, unsigned int cmd,
	unsigned long arg)
	{
	struct sync_file *sync_file = file->private_data;

	switch (cmd) {
	case SYNC_IOC_MERGE:
	return sync_file_ioctl_merge(sync_file, arg);

	case SYNC_IOC_FILE_INFO:
	return sync_file_ioctl_fence_info(sync_file, arg);

	default:
	return -ENOTTY;
	}
	}

	static const struct file_operations sync_file_fops = {
	.release = sync_file_release,
	.poll = sync_file_poll,
	.unlocked_ioctl = sync_file_ioctl,
	.compat_ioctl = sync_file_ioctl,
	};