/*
 * 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->flags))
                dma_fence_remove_callback(sync_file->fence, &sync_file->cb);
        dma_fence_put(sync_file->fence);
        kfree(sync_file);

        return 0;
}

static __poll_t 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 (list_empty(&sync_file->cb.node) &&
            !test_and_set_bit(POLL_ENABLED, &sync_file->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) ? EPOLLIN : 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 int 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);
        while (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) &&
               !test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags))
                cpu_relax();
        info->timestamp_ns =
                test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags) ?
                ktime_to_ns(fence->timestamp) :
                ktime_set(0, 0);

        return info->status;
}

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) {
                info.status = dma_fence_is_signaled(sync_file->fence);
                goto no_fences;
        } else {
                info.status = 1;
        }

        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++) {
                int status = sync_fill_fence_info(fences[i], &fence_info[i]);
                info.status = info.status <= 0 ? info.status : status;
        }

        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.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,
};