xref: /device/soc/rockchip/common/sdk_linux/drivers/dma-buf/dma-buf.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Framework for buffer objects that can be shared across devices/subsystems.
 *
 * Copyright(C) 2011 Linaro Limited. All rights reserved.
 * Author: Sumit Semwal <sumit.semwal@ti.com>
 *
 * Many thanks to linaro-mm-sig list, and specially
 * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
 * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
 * refining of this idea.
 */

#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/dma-buf.h>
#include <linux/dma-fence.h>
#include <linux/anon_inodes.h>
#include <linux/export.h>
#include <linux/debugfs.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/poll.h>
#include <linux/dma-resv.h>
#include <linux/mm.h>
#include <linux/mount.h>
#include <linux/pseudo_fs.h>

#include <uapi/linux/dma-buf.h>
#include <uapi/linux/magic.h>

#include "dma-buf-sysfs-stats.h"
#include "dma-buf-process-info.h"

struct dma_buf_list {
    struct list_head head;
    struct mutex lock;
};

static struct dma_buf_list db_list;

/*
 * This function helps in traversing the db_list and calls the
 * callback function which can extract required info out of each
 * dmabuf.
 */
int get_each_dmabuf(int (*callback)(const struct dma_buf *dmabuf, void *private), void *private)
{
    struct dma_buf *buf;
    int ret = mutex_lock_interruptible(&db_list.lock);
    if (ret) {
        return ret;
    }

    list_for_each_entry(buf, &db_list.head, list_node)
    {
        ret = callback(buf, private);
        if (ret) {
            break;
        }
    }
    mutex_unlock(&db_list.lock);
    return ret;
}
EXPORT_SYMBOL_GPL(get_each_dmabuf);

static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
{
    struct dma_buf *dmabuf;
    char name[DMA_BUF_NAME_LEN];
    size_t ret = 0;

    dmabuf = dentry->d_fsdata;
    spin_lock(&dmabuf->name_lock);
    if (dmabuf->name) {
        ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
    }
    spin_unlock(&dmabuf->name_lock);

    return dynamic_dname(dentry, buffer, buflen, "/%s:%s", dentry->d_name.name, ret > 0 ? name : "");
}

static void dma_buf_release(struct dentry *dentry)
{
    struct dma_buf *dmabuf;

    dmabuf = dentry->d_fsdata;
    if (unlikely(!dmabuf)) {
        return;
    }

    BUG_ON(dmabuf->vmapping_counter);

    /*
     * Any fences that a dma-buf poll can wait on should be signaled
     * before releasing dma-buf. This is the responsibility of each
     * driver that uses the reservation objects.
     *
     * If you hit this BUG() it means someone dropped their ref to the
     * dma-buf while still having pending operation to the buffer.
     */
    BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active);

    dmabuf->ops->release(dmabuf);

    if (dmabuf->resv == (struct dma_resv *)&dmabuf[1]) {
        dma_resv_fini(dmabuf->resv);
    }

    WARN_ON(!list_empty(&dmabuf->attachments));
    dma_buf_stats_teardown(dmabuf);
    module_put(dmabuf->owner);
    kfree(dmabuf->name);
    kfree(dmabuf);
}

static int dma_buf_file_release(struct inode *inode, struct file *file)
{
    struct dma_buf *dmabuf;

    if (!is_dma_buf_file(file)) {
        return -EINVAL;
    }

    dmabuf = file->private_data;

    mutex_lock(&db_list.lock);
    list_del(&dmabuf->list_node);
    mutex_unlock(&db_list.lock);

    return 0;
}

static const struct dentry_operations dma_buf_dentry_ops = {
    .d_dname = dmabuffs_dname,
    .d_release = dma_buf_release,
};

static struct vfsmount *dma_buf_mnt;

static int dma_buf_fs_init_context(struct fs_context *fc)
{
    struct pseudo_fs_context *ctx;

    ctx = init_pseudo(fc, DMA_BUF_MAGIC);
    if (!ctx) {
        return -ENOMEM;
    }
    ctx->dops = &dma_buf_dentry_ops;
    return 0;
}

static struct file_system_type dma_buf_fs_type = {
    .name = "dmabuf",
    .init_fs_context = dma_buf_fs_init_context,
    .kill_sb = kill_anon_super,
};

#ifdef CONFIG_DMABUF_SYSFS_STATS
static void dma_buf_vma_open(struct vm_area_struct *vma)
{
    struct dma_buf *dmabuf = vma->vm_file->private_data;

    dmabuf->mmap_count++;
    /* call the heap provided vma open() op */
    if (dmabuf->exp_vm_ops->open) {
        dmabuf->exp_vm_ops->open(vma);
    }
}

static void dma_buf_vma_close(struct vm_area_struct *vma)
{
    struct dma_buf *dmabuf = vma->vm_file->private_data;

    if (dmabuf->mmap_count) {
        dmabuf->mmap_count--;
    }
    /* call the heap provided vma close() op */
    if (dmabuf->exp_vm_ops->close) {
        dmabuf->exp_vm_ops->close(vma);
    }
}

static int dma_buf_do_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
{
    /* call this first because the exporter might override vma->vm_ops */
    int ret = dmabuf->ops->mmap(dmabuf, vma);
    if (ret) {
        return ret;
    }

    /* save the exporter provided vm_ops */
    dmabuf->exp_vm_ops = vma->vm_ops;
    dmabuf->vm_ops = *(dmabuf->exp_vm_ops);
    /* override open() and close() to provide buffer mmap count */
    dmabuf->vm_ops.open = dma_buf_vma_open;
    dmabuf->vm_ops.close = dma_buf_vma_close;
    vma->vm_ops = &dmabuf->vm_ops;
    dmabuf->mmap_count++;

    return ret;
}
#else  /* CONFIG_DMABUF_SYSFS_STATS */
static int dma_buf_do_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
{
    return dmabuf->ops->mmap(dmabuf, vma);
}
#endif /* CONFIG_DMABUF_SYSFS_STATS */

static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
{
    struct dma_buf *dmabuf;

    if (!is_dma_buf_file(file)) {
        return -EINVAL;
    }

    dmabuf = file->private_data;

    /* check if buffer supports mmap */
    if (!dmabuf->ops->mmap) {
        return -EINVAL;
    }

    /* check for overflowing the buffer's size */
    if ((vma->vm_pgoff + vma_pages(vma)) > (dmabuf->size >> PAGE_SHIFT)) {
        return -EINVAL;
    }

    return dma_buf_do_mmap(dmabuf, vma);
}

static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
{
    struct dma_buf *dmabuf;
    loff_t base;

    if (!is_dma_buf_file(file)) {
        return -EBADF;
    }

    dmabuf = file->private_data;

    /* only support discovering the end of the buffer,
       but also allow SEEK_SET to maintain the idiomatic
       SEEK_END(0), SEEK_CUR(0) pattern */
    if (whence == SEEK_END) {
        base = dmabuf->size;
    } else if (whence == SEEK_SET) {
        base = 0;
    } else {
        return -EINVAL;
    }

    if (offset != 0) {
        return -EINVAL;
    }

    return base + offset;
}

/**
 * DOC: implicit fence polling
 *
 * To support cross-device and cross-driver synchronization of buffer access
 * implicit fences (represented internally in the kernel with &struct dma_fence)
 * can be attached to a &dma_buf. The glue for that and a few related things are
 * provided in the &dma_resv structure.
 *
 * Userspace can query the state of these implicitly tracked fences using poll()
 * and related system calls
 *
 * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
 *   most recent write or exclusive fence.
 *
 * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
 *   all attached fences, shared and exclusive ones.
 *
 * Note that this only signals the completion of the respective fences, i.e. the
 * DMA transfers are complete. Cache flushing and any other necessary
 * preparations before CPU access can begin still need to happen.
 */

static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
{
    struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
    unsigned long flags;

    spin_lock_irqsave(&dcb->poll->lock, flags);
    wake_up_locked_poll(dcb->poll, dcb->active);
    dcb->active = 0;
    spin_unlock_irqrestore(&dcb->poll->lock, flags);
}

static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
{
    struct dma_buf *dmabuf;
    struct dma_resv *resv;
    struct dma_resv_list *fobj;
    struct dma_fence *fence_excl;
    __poll_t events;
    unsigned shared_count, seq;

    dmabuf = file->private_data;
    if (!dmabuf || !dmabuf->resv) {
        return EPOLLERR;
    }

    resv = dmabuf->resv;

    poll_wait(file, &dmabuf->poll, poll);

    events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
    if (!events) {
        return 0;
    }

    while (1) {
        seq = read_seqcount_begin(&resv->seq);
        rcu_read_lock();

        fobj = rcu_dereference(resv->fence);
        if (fobj) {
            shared_count = fobj->shared_count;
        } else {
            shared_count = 0;
        }
        fence_excl = rcu_dereference(resv->fence_excl);
        if (read_seqcount_retry(&resv->seq, seq)) {
            rcu_read_unlock();
            continue;
        }
        break;
    }
    if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) {
        struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
        __poll_t pevents = EPOLLIN;

        if (shared_count == 0) {
            pevents |= EPOLLOUT;
        }

        spin_lock_irq(&dmabuf->poll.lock);
        if (dcb->active) {
            dcb->active |= pevents;
            events &= ~pevents;
        } else {
            dcb->active = pevents;
        }
        spin_unlock_irq(&dmabuf->poll.lock);

        if (events & pevents) {
            if (!dma_fence_get_rcu(fence_excl)) {
                /* force a recheck */
                events &= ~pevents;
                dma_buf_poll_cb(NULL, &dcb->cb);
            } else if (!dma_fence_add_callback(fence_excl, &dcb->cb, dma_buf_poll_cb)) {
                events &= ~pevents;
                dma_fence_put(fence_excl);
            } else {
                /*
                 * No callback queued, wake up any additional
                 * waiters.
                 */
                dma_fence_put(fence_excl);
                dma_buf_poll_cb(NULL, &dcb->cb);
            }
        }
    }

    if ((events & EPOLLOUT) && shared_count > 0) {
        struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
        int i;

        /* Only queue a new callback if no event has fired yet */
        spin_lock_irq(&dmabuf->poll.lock);
        if (dcb->active) {
            events &= ~EPOLLOUT;
        } else {
            dcb->active = EPOLLOUT;
        }
        spin_unlock_irq(&dmabuf->poll.lock);

        if (!(events & EPOLLOUT)) {
            goto out;
        }

        for (i = 0; i < shared_count; ++i) {
            struct dma_fence *fence = rcu_dereference(fobj->shared[i]);

            if (!dma_fence_get_rcu(fence)) {
                /*
                 * fence refcount dropped to zero, this means
                 * that fobj has been freed
                 *
                 * call dma_buf_poll_cb and force a recheck!
                 */
                events &= ~EPOLLOUT;
                dma_buf_poll_cb(NULL, &dcb->cb);
                break;
            }
            if (!dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb)) {
                dma_fence_put(fence);
                events &= ~EPOLLOUT;
                break;
            }
            dma_fence_put(fence);
        }

        /* No callback queued, wake up any additional waiters. */
        if (i == shared_count) {
            dma_buf_poll_cb(NULL, &dcb->cb);
        }
    }

out:
    rcu_read_unlock();
    return events;
}

/**
 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
 * The name of the dma-buf buffer can only be set when the dma-buf is not
 * attached to any devices. It could theoritically support changing the
 * name of the dma-buf if the same piece of memory is used for multiple
 * purpose between different devices.
 *
 * @dmabuf: [in]     dmabuf buffer that will be renamed.
 * @buf:    [in]     A piece of userspace memory that contains the name of
 *                   the dma-buf.
 *
 * Returns 0 on success. If the dma-buf buffer is already attached to
 * devices, return -EBUSY.
 *
 */
static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
{
    char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
    long ret = 0;

    if (IS_ERR(name)) {
        return PTR_ERR(name);
    }

    dma_resv_lock(dmabuf->resv, NULL);
    if (!list_empty(&dmabuf->attachments)) {
        ret = -EBUSY;
        kfree(name);
        goto out_unlock;
    }
    spin_lock(&dmabuf->name_lock);
    kfree(dmabuf->name);
    dmabuf->name = name;
    spin_unlock(&dmabuf->name_lock);

out_unlock:
    dma_resv_unlock(dmabuf->resv);
    return ret;
}

static long dma_buf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    struct dma_buf *dmabuf;
    struct dma_buf_sync sync;
    enum dma_data_direction direction;
    int ret;

    dmabuf = file->private_data;

    switch (cmd) {
        case DMA_BUF_IOCTL_SYNC:
            if (copy_from_user(&sync, (void __user *)arg, sizeof(sync))) {
                return -EFAULT;
            }

            if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK) {
                return -EINVAL;
            }

            switch (sync.flags & DMA_BUF_SYNC_RW) {
                case DMA_BUF_SYNC_READ:
                    direction = DMA_FROM_DEVICE;
                    break;
                case DMA_BUF_SYNC_WRITE:
                    direction = DMA_TO_DEVICE;
                    break;
                case DMA_BUF_SYNC_RW:
                    direction = DMA_BIDIRECTIONAL;
                    break;
                default:
                    return -EINVAL;
            }

            if (sync.flags & DMA_BUF_SYNC_END) {
                ret = dma_buf_end_cpu_access(dmabuf, direction);
            } else {
                ret = dma_buf_begin_cpu_access(dmabuf, direction);
            }

            return ret;

        case DMA_BUF_SET_NAME_A:
        case DMA_BUF_SET_NAME_B:
            return dma_buf_set_name(dmabuf, (const char __user *)arg);

        default:
            return -ENOTTY;
    }
}

static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
{
    struct dma_buf *dmabuf = file->private_data;

    seq_printf(m, "size:\t%zu\n", dmabuf->size);
    /* Don't count the temporary reference taken inside procfs seq_show */
    seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
    seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
    spin_lock(&dmabuf->name_lock);
    if (dmabuf->name) {
        seq_printf(m, "name:\t%s\n", dmabuf->name);
    }
    spin_unlock(&dmabuf->name_lock);
}

static const struct file_operations dma_buf_fops = {
    .release = dma_buf_file_release,
    .mmap = dma_buf_mmap_internal,
    .llseek = dma_buf_llseek,
    .poll = dma_buf_poll,
    .unlocked_ioctl = dma_buf_ioctl,
    .compat_ioctl = compat_ptr_ioctl,
    .show_fdinfo = dma_buf_show_fdinfo,
};

/*
 * is_dma_buf_file - Check if struct file* is associated with dma_buf
 */
int is_dma_buf_file(struct file *file)
{
    return file->f_op == &dma_buf_fops;
}
EXPORT_SYMBOL_GPL(is_dma_buf_file);

static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
{
    struct file *file;
    struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);

    if (IS_ERR(inode)) {
        return ERR_CAST(inode);
    }

    inode->i_size = dmabuf->size;
    inode_set_bytes(inode, dmabuf->size);

    file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf", flags, &dma_buf_fops);
    if (IS_ERR(file)) {
        goto err_alloc_file;
    }
    file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
    file->private_data = dmabuf;
    file->f_path.dentry->d_fsdata = dmabuf;

    return file;

err_alloc_file:
    iput(inode);
    return file;
}

/**
 * DOC: dma buf device access
 *
 * For device DMA access to a shared DMA buffer the usual sequence of operations
 * is fairly simple
 *
 * 1. The exporter defines his exporter instance using
 *    DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
 *    buffer object into a &dma_buf. It then exports that &dma_buf to userspace
 *    as a file descriptor by calling dma_buf_fd().
 *
 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
 *    to share with: First the filedescriptor is converted to a &dma_buf using
 *    dma_buf_get(). Then the buffer is attached to the device using
 *    dma_buf_attach().
 *
 *    Up to this stage the exporter is still free to migrate or reallocate the
 *    backing storage.
 *
 * 3. Once the buffer is attached to all devices userspace can initiate DMA
 *    access to the shared buffer. In the kernel this is done by calling
 *    dma_buf_map_attachment() and dma_buf_unmap_attachment().
 *
 * 4. Once a driver is done with a shared buffer it needs to call
 *    dma_buf_detach() (after cleaning up any mappings) and then release the
 *    reference acquired with dma_buf_get by calling dma_buf_put().
 *
 * For the detailed semantics exporters are expected to implement see
 * &dma_buf_ops.
 */

/**
 * dma_buf_export - Creates a new dma_buf, and associates an anon file
 * with this buffer, so it can be exported.
 * Also connect the allocator specific data and ops to the buffer.
 * Additionally, provide a name string for exporter; useful in debugging.
 *
 * @exp_info:    [in]    holds all the export related information provided
 *            by the exporter. see &struct dma_buf_export_info
 *            for further details.
 *
 * Returns, on success, a newly created dma_buf object, which wraps the
 * supplied private data and operations for dma_buf_ops. On either missing
 * ops, or error in allocating struct dma_buf, will return negative error.
 *
 * For most cases the easiest way to create @exp_info is through the
 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
 */
struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
{
    struct dma_buf *dmabuf;
    struct dma_resv *resv = exp_info->resv;
    struct file *file;
    size_t alloc_size = sizeof(struct dma_buf);
    int ret;

    if (!exp_info->resv) {
        alloc_size += sizeof(struct dma_resv);
    } else {
        /* prevent &dma_buf[1] == dma_buf->resv */
        alloc_size += 1;
    }

    if (WARN_ON(!exp_info->priv || !exp_info->ops || !exp_info->ops->map_dma_buf || !exp_info->ops->unmap_dma_buf ||
                !exp_info->ops->release)) {
        return ERR_PTR(-EINVAL);
    }

    if (WARN_ON(exp_info->ops->cache_sgt_mapping && (exp_info->ops->pin || exp_info->ops->unpin))) {
        return ERR_PTR(-EINVAL);
    }

    if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin)) {
        return ERR_PTR(-EINVAL);
    }

    if (!try_module_get(exp_info->owner)) {
        return ERR_PTR(-ENOENT);
    }

    dmabuf = kzalloc(alloc_size, GFP_KERNEL);
    if (!dmabuf) {
        ret = -ENOMEM;
        goto err_module;
    }

    dmabuf->priv = exp_info->priv;
    dmabuf->ops = exp_info->ops;
    dmabuf->size = exp_info->size;
    dmabuf->exp_name = exp_info->exp_name;
    dmabuf->owner = exp_info->owner;
    spin_lock_init(&dmabuf->name_lock);
    init_waitqueue_head(&dmabuf->poll);
    dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
    dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;

    if (!resv) {
        resv = (struct dma_resv *)&dmabuf[1];
        dma_resv_init(resv);
    }
    dmabuf->resv = resv;

    file = dma_buf_getfile(dmabuf, exp_info->flags);
    if (IS_ERR(file)) {
        ret = PTR_ERR(file);
        goto err_dmabuf;
    }

    file->f_mode |= FMODE_LSEEK;
    dmabuf->file = file;

    ret = dma_buf_stats_setup(dmabuf);
    if (ret) {
        goto err_sysfs;
    }

    mutex_init(&dmabuf->lock);
    INIT_LIST_HEAD(&dmabuf->attachments);

    mutex_lock(&db_list.lock);
    list_add(&dmabuf->list_node, &db_list.head);
    mutex_unlock(&db_list.lock);

    init_dma_buf_task_info(dmabuf);
    return dmabuf;

err_sysfs:
    /*
     * Set file->f_path.dentry->d_fsdata to NULL so that when
     * dma_buf_release() gets invoked by dentry_ops, it exits
     * early before calling the release() dma_buf op.
     */
    file->f_path.dentry->d_fsdata = NULL;
    fput(file);
err_dmabuf:
    kfree(dmabuf);
err_module:
    module_put(exp_info->owner);
    return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(dma_buf_export);

/**
 * dma_buf_fd - returns a file descriptor for the given dma_buf
 * @dmabuf:    [in]    pointer to dma_buf for which fd is required.
 * @flags:      [in]    flags to give to fd
 *
 * On success, returns an associated 'fd'. Else, returns error.
 */
int dma_buf_fd(struct dma_buf *dmabuf, int flags)
{
    int fd;

    if (!dmabuf || !dmabuf->file) {
        return -EINVAL;
    }

    fd = get_unused_fd_flags(flags);
    if (fd < 0) {
        return fd;
    }

    fd_install(fd, dmabuf->file);

    return fd;
}
EXPORT_SYMBOL_GPL(dma_buf_fd);

/**
 * dma_buf_get - returns the dma_buf structure related to an fd
 * @fd:    [in]    fd associated with the dma_buf to be returned
 *
 * On success, returns the dma_buf structure associated with an fd; uses
 * file's refcounting done by fget to increase refcount. returns ERR_PTR
 * otherwise.
 */
struct dma_buf *dma_buf_get(int fd)
{
    struct file *file;

    file = fget(fd);
    if (!file) {
        return ERR_PTR(-EBADF);
    }

    if (!is_dma_buf_file(file)) {
        fput(file);
        return ERR_PTR(-EINVAL);
    }

    return file->private_data;
}
EXPORT_SYMBOL_GPL(dma_buf_get);

/**
 * dma_buf_put - decreases refcount of the buffer
 * @dmabuf:    [in]    buffer to reduce refcount of
 *
 * Uses file's refcounting done implicitly by fput().
 *
 * If, as a result of this call, the refcount becomes 0, the 'release' file
 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
 * in turn, and frees the memory allocated for dmabuf when exported.
 */
void dma_buf_put(struct dma_buf *dmabuf)
{
    if (WARN_ON(!dmabuf || !dmabuf->file)) {
        return;
    }

    fput(dmabuf->file);
}
EXPORT_SYMBOL_GPL(dma_buf_put);

/**
 * dma_buf_pin - Lock down the DMA-buf
 *
 * @attach:    [in]    attachment which should be pinned
 *
 * Returns:
 * 0 on success, negative error code on failure.
 */
int dma_buf_pin(struct dma_buf_attachment *attach)
{
    struct dma_buf *dmabuf = attach->dmabuf;
    int ret = 0;

    dma_resv_assert_held(dmabuf->resv);

    if (dmabuf->ops->pin) {
        ret = dmabuf->ops->pin(attach);
    }

    return ret;
}
EXPORT_SYMBOL_GPL(dma_buf_pin);

/**
 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list; optionally,
 * calls attach() of dma_buf_ops to allow device-specific attach functionality
 * @dmabuf:        [in]    buffer to attach device to.
 * @dev:        [in]    device to be attached.
 * @importer_ops:    [in]    importer operations for the attachment
 * @importer_priv:    [in]    importer private pointer for the attachment
 *
 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
 * must be cleaned up by calling dma_buf_detach().
 *
 * Returns
 *
 * A pointer to newly created &dma_buf_attachment on success, or a negative
 * error code wrapped into a pointer on failure.
 *
 * Note that this can fail if the backing storage of @dmabuf is in a place not
 * accessible to @dev, and cannot be moved to a more suitable place. This is
 * indicated with the error code -EBUSY.
 */
struct dma_buf_attachment *dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
                                                  const struct dma_buf_attach_ops *importer_ops, void *importer_priv)
{
    struct dma_buf_attachment *attach;
    int ret;

    if (WARN_ON(!dmabuf || !dev)) {
        return ERR_PTR(-EINVAL);
    }

    if (WARN_ON(importer_ops && !importer_ops->move_notify)) {
        return ERR_PTR(-EINVAL);
    }

    attach = kzalloc(sizeof(*attach), GFP_KERNEL);
    if (!attach) {
        return ERR_PTR(-ENOMEM);
    }

    attach->dev = dev;
    attach->dmabuf = dmabuf;
    if (importer_ops) {
        attach->peer2peer = importer_ops->allow_peer2peer;
    }
    attach->importer_ops = importer_ops;
    attach->importer_priv = importer_priv;

    if (dmabuf->ops->attach) {
        ret = dmabuf->ops->attach(dmabuf, attach);
        if (ret) {
            goto err_attach;
        }
    }
    dma_resv_lock(dmabuf->resv, NULL);
    list_add(&attach->node, &dmabuf->attachments);
    dma_resv_unlock(dmabuf->resv);

    /* When either the importer or the exporter can't handle dynamic
     * mappings we cache the mapping here to avoid issues with the
     * reservation object lock.
     */
    if (dma_buf_attachment_is_dynamic(attach) != dma_buf_is_dynamic(dmabuf)) {
        struct sg_table *sgt;

        if (dma_buf_is_dynamic(attach->dmabuf)) {
            dma_resv_lock(attach->dmabuf->resv, NULL);
            ret = dma_buf_pin(attach);
            if (ret) {
                goto err_unlock;
            }
        }

        sgt = dmabuf->ops->map_dma_buf(attach, DMA_BIDIRECTIONAL);
        if (!sgt) {
            sgt = ERR_PTR(-ENOMEM);
        }
        if (IS_ERR(sgt)) {
            ret = PTR_ERR(sgt);
            goto err_unpin;
        }
        if (dma_buf_is_dynamic(attach->dmabuf)) {
            dma_resv_unlock(attach->dmabuf->resv);
        }
        attach->sgt = sgt;
        attach->dir = DMA_BIDIRECTIONAL;
    }

    return attach;

err_attach:
    kfree(attach);
    return ERR_PTR(ret);

err_unpin:
    if (dma_buf_is_dynamic(attach->dmabuf)) {
        dma_buf_unpin(attach);
    }

err_unlock:
    if (dma_buf_is_dynamic(attach->dmabuf)) {
        dma_resv_unlock(attach->dmabuf->resv);
    }

    dma_buf_detach(dmabuf, attach);
    return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(dma_buf_dynamic_attach);

/**
 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
 * @dmabuf:    [in]    buffer to attach device to.
 * @dev:    [in]    device to be attached.
 *
 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
 * mapping.
 */
struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, struct device *dev)
{
    return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
}
EXPORT_SYMBOL_GPL(dma_buf_attach);

/**
 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
 * optionally calls detach() of dma_buf_ops for device-specific detach
 * @dmabuf:    [in]    buffer to detach from.
 * @attach:    [in]    attachment to be detached; is free'd after this call.
 *
 * Clean up a device attachment obtained by calling dma_buf_attach().
 */
void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
{
    if (WARN_ON(!dmabuf || !attach)) {
        return;
    }

    if (attach->sgt) {
        if (dma_buf_is_dynamic(attach->dmabuf)) {
            dma_resv_lock(attach->dmabuf->resv, NULL);
        }

        dmabuf->ops->unmap_dma_buf(attach, attach->sgt, attach->dir);

        if (dma_buf_is_dynamic(attach->dmabuf)) {
            dma_buf_unpin(attach);
            dma_resv_unlock(attach->dmabuf->resv);
        }
    }

    dma_resv_lock(dmabuf->resv, NULL);
    list_del(&attach->node);
    dma_resv_unlock(dmabuf->resv);
    if (dmabuf->ops->detach) {
        dmabuf->ops->detach(dmabuf, attach);
    }

    kfree(attach);
}
EXPORT_SYMBOL_GPL(dma_buf_detach);

/**
 * dma_buf_unpin - Remove lock from DMA-buf
 *
 * @attach:    [in]    attachment which should be unpinned
 */
void dma_buf_unpin(struct dma_buf_attachment *attach)
{
    struct dma_buf *dmabuf = attach->dmabuf;

    dma_resv_assert_held(dmabuf->resv);

    if (dmabuf->ops->unpin) {
        dmabuf->ops->unpin(attach);
    }
}
EXPORT_SYMBOL_GPL(dma_buf_unpin);

/**
 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
 * dma_buf_ops.
 * @attach:    [in]    attachment whose scatterlist is to be returned
 * @direction:    [in]    direction of DMA transfer
 *
 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
 * on error. May return -EINTR if it is interrupted by a signal.
 *
 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
 * the underlying backing storage is pinned for as long as a mapping exists,
 * therefore users/importers should not hold onto a mapping for undue amounts of
 * time.
 */
struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, enum dma_data_direction direction)
{
    struct sg_table *sg_table;
    int r;

    might_sleep();

    if (WARN_ON(!attach || !attach->dmabuf)) {
        return ERR_PTR(-EINVAL);
    }

    if (dma_buf_attachment_is_dynamic(attach)) {
        dma_resv_assert_held(attach->dmabuf->resv);
    }

    if (attach->sgt) {
        /*
         * Two mappings with different directions for the same
         * attachment are not allowed.
         */
        if (attach->dir != direction && attach->dir != DMA_BIDIRECTIONAL) {
            return ERR_PTR(-EBUSY);
        }

        return attach->sgt;
    }

    if (dma_buf_is_dynamic(attach->dmabuf)) {
        dma_resv_assert_held(attach->dmabuf->resv);
        if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
            r = dma_buf_pin(attach);
            if (r) {
                return ERR_PTR(r);
            }
        }
    }

    sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
    if (!sg_table) {
        sg_table = ERR_PTR(-ENOMEM);
    }

    if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) && !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
        dma_buf_unpin(attach);
    }

    if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
        attach->sgt = sg_table;
        attach->dir = direction;
    }

    return sg_table;
}
EXPORT_SYMBOL_GPL(dma_buf_map_attachment);

/**
 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
 * dma_buf_ops.
 * @attach:    [in]    attachment to unmap buffer from
 * @sg_table:    [in]    scatterlist info of the buffer to unmap
 * @direction:  [in]    direction of DMA transfer
 *
 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
 */
void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, struct sg_table *sg_table,
                              enum dma_data_direction direction)
{
    might_sleep();

    if (WARN_ON(!attach || !attach->dmabuf || !sg_table)) {
        return;
    }

    if (dma_buf_attachment_is_dynamic(attach)) {
        dma_resv_assert_held(attach->dmabuf->resv);
    }

    if (attach->sgt == sg_table) {
        return;
    }

    if (dma_buf_is_dynamic(attach->dmabuf)) {
        dma_resv_assert_held(attach->dmabuf->resv);
    }

    attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);

    if (dma_buf_is_dynamic(attach->dmabuf) && !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
        dma_buf_unpin(attach);
    }
}
EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);

/**
 * dma_buf_move_notify - notify attachments that DMA-buf is moving
 *
 * @dmabuf:    [in]    buffer which is moving
 *
 * Informs all attachmenst that they need to destroy and recreated all their
 * mappings.
 */
void dma_buf_move_notify(struct dma_buf *dmabuf)
{
    struct dma_buf_attachment *attach;

    dma_resv_assert_held(dmabuf->resv);

    list_for_each_entry(attach, &dmabuf->attachments, node) if (attach->importer_ops)
        attach->importer_ops->move_notify(attach);
}
EXPORT_SYMBOL_GPL(dma_buf_move_notify);

/**
 * DOC: cpu access
 *
 * There are mutliple reasons for supporting CPU access to a dma buffer object:
 *
 * - Fallback operations in the kernel, for example when a device is connected
 *   over USB and the kernel needs to shuffle the data around first before
 *   sending it away. Cache coherency is handled by braketing any transactions
 *   with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
 *   access.
 *
 *   Since for most kernel internal dma-buf accesses need the entire buffer, a
 *   vmap interface is introduced. Note that on very old 32-bit architectures
 *   vmalloc space might be limited and result in vmap calls failing.
 *
 *   Interfaces::
 *      void \*dma_buf_vmap(struct dma_buf \*dmabuf)
 *      void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
 *
 *   The vmap call can fail if there is no vmap support in the exporter, or if
 *   it runs out of vmalloc space. Fallback to kmap should be implemented. Note
 *   that the dma-buf layer keeps a reference count for all vmap access and
 *   calls down into the exporter's vmap function only when no vmapping exists,
 *   and only unmaps it once. Protection against concurrent vmap/vunmap calls is
 *   provided by taking the dma_buf->lock mutex.
 *
 * - For full compatibility on the importer side with existing userspace
 *   interfaces, which might already support mmap'ing buffers. This is needed in
 *   many processing pipelines (e.g. feeding a software rendered image into a
 *   hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
 *   framework already supported this and for DMA buffer file descriptors to
 *   replace ION buffers mmap support was needed.
 *
 *   There is no special interfaces, userspace simply calls mmap on the dma-buf
 *   fd. But like for CPU access there's a need to braket the actual access,
 *   which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
 *   DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
 *   be restarted.
 *
 *   Some systems might need some sort of cache coherency management e.g. when
 *   CPU and GPU domains are being accessed through dma-buf at the same time.
 *   To circumvent this problem there are begin/end coherency markers, that
 *   forward directly to existing dma-buf device drivers vfunc hooks. Userspace
 *   can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
 *   sequence would be used like following:
 *
 *     - mmap dma-buf fd
 *     - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
 *       to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
 *       want (with the new data being consumed by say the GPU or the scanout
 *       device)
 *     - munmap once you don't need the buffer any more
 *
 *    For correctness and optimal performance, it is always required to use
 *    SYNC_START and SYNC_END before and after, respectively, when accessing the
 *    mapped address. Userspace cannot rely on coherent access, even when there
 *    are systems where it just works without calling these ioctls.
 *
 * - And as a CPU fallback in userspace processing pipelines.
 *
 *   Similar to the motivation for kernel cpu access it is again important that
 *   the userspace code of a given importing subsystem can use the same
 *   interfaces with a imported dma-buf buffer object as with a native buffer
 *   object. This is especially important for drm where the userspace part of
 *   contemporary OpenGL, X, and other drivers is huge, and reworking them to
 *   use a different way to mmap a buffer rather invasive.
 *
 *   The assumption in the current dma-buf interfaces is that redirecting the
 *   initial mmap is all that's needed. A survey of some of the existing
 *   subsystems shows that no driver seems to do any nefarious thing like
 *   syncing up with outstanding asynchronous processing on the device or
 *   allocating special resources at fault time. So hopefully this is good
 *   enough, since adding interfaces to intercept pagefaults and allow pte
 *   shootdowns would increase the complexity quite a bit.
 *
 *   Interface::
 *      int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
 *               unsigned long);
 *
 *   If the importing subsystem simply provides a special-purpose mmap call to
 *   set up a mapping in userspace, calling do_mmap with dma_buf->file will
 *   equally achieve that for a dma-buf object.
 */

static int _dma_buf_begin_cpu_access(struct dma_buf *dmabuf, enum dma_data_direction direction)
{
    bool write = (direction == DMA_BIDIRECTIONAL || direction == DMA_TO_DEVICE);
    struct dma_resv *resv = dmabuf->resv;
    long ret;

    /* Wait on any implicit rendering fences */
    ret = dma_resv_wait_timeout_rcu(resv, write, true, MAX_SCHEDULE_TIMEOUT);
    if (ret < 0) {
        return ret;
    }

    return 0;
}

/**
 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
 * preparations. Coherency is only guaranteed in the specified range for the
 * specified access direction.
 * @dmabuf:    [in]    buffer to prepare cpu access for.
 * @direction:    [in]    length of range for cpu access.
 *
 * After the cpu access is complete the caller should call
 * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
 * it guaranteed to be coherent with other DMA access.
 *
 * Can return negative error values, returns 0 on success.
 */
int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, enum dma_data_direction direction)
{
    int ret = 0;

    if (WARN_ON(!dmabuf)) {
        return -EINVAL;
    }

    if (dmabuf->ops->begin_cpu_access) {
        ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
    }

    /* Ensure that all fences are waited upon - but we first allow
     * the native handler the chance to do so more efficiently if it
     * chooses. A double invocation here will be reasonably cheap no-op.
     */
    if (ret == 0) {
        ret = _dma_buf_begin_cpu_access(dmabuf, direction);
    }

    return ret;
}
EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);

int dma_buf_begin_cpu_access_partial(struct dma_buf *dmabuf, enum dma_data_direction direction, unsigned int offset,
                                     unsigned int len)
{
    int ret = 0;

    if (WARN_ON(!dmabuf)) {
        return -EINVAL;
    }

    if (dmabuf->ops->begin_cpu_access_partial) {
        ret = dmabuf->ops->begin_cpu_access_partial(dmabuf, direction, offset, len);
    }

    /* Ensure that all fences are waited upon - but we first allow
     * the native handler the chance to do so more efficiently if it
     * chooses. A double invocation here will be reasonably cheap no-op.
     */
    if (ret == 0) {
        ret = _dma_buf_begin_cpu_access(dmabuf, direction);
    }

    return ret;
}
EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access_partial);

/**
 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
 * actions. Coherency is only guaranteed in the specified range for the
 * specified access direction.
 * @dmabuf:    [in]    buffer to complete cpu access for.
 * @direction:    [in]    length of range for cpu access.
 *
 * This terminates CPU access started with dma_buf_begin_cpu_access().
 *
 * Can return negative error values, returns 0 on success.
 */
int dma_buf_end_cpu_access(struct dma_buf *dmabuf, enum dma_data_direction direction)
{
    int ret = 0;

    WARN_ON(!dmabuf);

    if (dmabuf->ops->end_cpu_access) {
        ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
    }

    return ret;
}
EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);

int dma_buf_end_cpu_access_partial(struct dma_buf *dmabuf, enum dma_data_direction direction, unsigned int offset,
                                   unsigned int len)
{
    int ret = 0;

    WARN_ON(!dmabuf);

    if (dmabuf->ops->end_cpu_access_partial) {
        ret = dmabuf->ops->end_cpu_access_partial(dmabuf, direction, offset, len);
    }

    return ret;
}
EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access_partial);

/**
 * dma_buf_mmap - Setup up a userspace mmap with the given vma
 * @dmabuf:    [in]    buffer that should back the vma
 * @vma:    [in]    vma for the mmap
 * @pgoff:    [in]    offset in pages where this mmap should start within the
 *            dma-buf buffer.
 *
 * This function adjusts the passed in vma so that it points at the file of the
 * dma_buf operation. It also adjusts the starting pgoff and does bounds
 * checking on the size of the vma. Then it calls the exporters mmap function to
 * set up the mapping.
 *
 * Can return negative error values, returns 0 on success.
 */
int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma, unsigned long pgoff)
{
    struct file *oldfile;
    int ret;

    if (WARN_ON(!dmabuf || !vma)) {
        return -EINVAL;
    }

    /* check if buffer supports mmap */
    if (!dmabuf->ops->mmap) {
        return -EINVAL;
    }

    /* check for offset overflow */
    if (pgoff + vma_pages(vma) < pgoff) {
        return -EOVERFLOW;
    }

    /* check for overflowing the buffer's size */
    if ((pgoff + vma_pages(vma)) > (dmabuf->size >> PAGE_SHIFT)) {
        return -EINVAL;
    }

    /* readjust the vma */
    get_file(dmabuf->file);
    oldfile = vma->vm_file;
    vma->vm_file = dmabuf->file;
    vma->vm_pgoff = pgoff;

    ret = dmabuf->ops->mmap(dmabuf, vma);
    if (ret) {
        /* restore old parameters on failure */
        vma->vm_file = oldfile;
        fput(dmabuf->file);
    } else {
        if (oldfile) {
            fput(oldfile);
        }
    }
    return ret;
}
EXPORT_SYMBOL_GPL(dma_buf_mmap);

/**
 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
 * address space. Same restrictions as for vmap and friends apply.
 * @dmabuf:    [in]    buffer to vmap
 *
 * This call may fail due to lack of virtual mapping address space.
 * These calls are optional in drivers. The intended use for them
 * is for mapping objects linear in kernel space for high use objects.
 * Please attempt to use kmap/kunmap before thinking about these interfaces.
 *
 * Returns NULL on error.
 */
void *dma_buf_vmap(struct dma_buf *dmabuf)
{
    void *ptr;

    if (WARN_ON(!dmabuf)) {
        return NULL;
    }

    if (!dmabuf->ops->vmap) {
        return NULL;
    }

    mutex_lock(&dmabuf->lock);
    if (dmabuf->vmapping_counter) {
        dmabuf->vmapping_counter++;
        BUG_ON(!dmabuf->vmap_ptr);
        ptr = dmabuf->vmap_ptr;
        goto out_unlock;
    }

    BUG_ON(dmabuf->vmap_ptr);

    ptr = dmabuf->ops->vmap(dmabuf);
    if (WARN_ON_ONCE(IS_ERR(ptr))) {
        ptr = NULL;
    }
    if (!ptr) {
        goto out_unlock;
    }

    dmabuf->vmap_ptr = ptr;
    dmabuf->vmapping_counter = 1;

out_unlock:
    mutex_unlock(&dmabuf->lock);
    return ptr;
}
EXPORT_SYMBOL_GPL(dma_buf_vmap);

/**
 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
 * @dmabuf:    [in]    buffer to vunmap
 * @vaddr:    [in]    vmap to vunmap
 */
void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
{
    if (WARN_ON(!dmabuf)) {
        return;
    }

    BUG_ON(!dmabuf->vmap_ptr);
    BUG_ON(dmabuf->vmapping_counter == 0);
    BUG_ON(dmabuf->vmap_ptr != vaddr);

    mutex_lock(&dmabuf->lock);
    if (--dmabuf->vmapping_counter == 0) {
        if (dmabuf->ops->vunmap) {
            dmabuf->ops->vunmap(dmabuf, vaddr);
        }
        dmabuf->vmap_ptr = NULL;
    }
    mutex_unlock(&dmabuf->lock);
}
EXPORT_SYMBOL_GPL(dma_buf_vunmap);

int dma_buf_get_flags(struct dma_buf *dmabuf, unsigned long *flags)
{
    int ret = 0;

    if (WARN_ON(!dmabuf) || !flags) {
        return -EINVAL;
    }

    if (dmabuf->ops->get_flags) {
        ret = dmabuf->ops->get_flags(dmabuf, flags);
    }

    return ret;
}
EXPORT_SYMBOL_GPL(dma_buf_get_flags);

int dma_buf_get_uuid(struct dma_buf *dmabuf, uuid_t *uuid)
{
    if (WARN_ON(!dmabuf) || !uuid) {
        return -EINVAL;
    }

    if (!dmabuf->ops->get_uuid) {
        return -ENODEV;
    }

    return dmabuf->ops->get_uuid(dmabuf, uuid);
}
EXPORT_SYMBOL_GPL(dma_buf_get_uuid);

#ifdef CONFIG_DEBUG_FS
static int dma_buf_debug_show(struct seq_file *s, void *unused)
{
    int ret;
    struct dma_buf *buf_obj;
    struct dma_buf_attachment *attach_obj;
    struct dma_resv *robj;
    struct dma_resv_list *fobj;
    struct dma_fence *fence;
    unsigned seq;
    int count = 0, attach_count, shared_count, i;
    size_t size = 0;

    ret = mutex_lock_interruptible(&db_list.lock);
    if (ret) {
        return ret;
    }

    seq_puts(s, "\nDma-buf Objects:\n");
    seq_printf(s,
               "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\t"
               "%-16s\t%-16s\t%-16s\n",
               "size", "flags", "mode", "count", "ino", "buf_name", "exp_pid", "exp_task_comm");

    list_for_each_entry(buf_obj, &db_list.head, list_node)
    {
        ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
        if (ret) {
            goto error_unlock;
        }

        seq_printf(s,
                   "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\t"
                   "%-16d\t%-16s\n",
                   buf_obj->size, buf_obj->file->f_flags, buf_obj->file->f_mode, file_count(buf_obj->file),
                   buf_obj->exp_name, file_inode(buf_obj->file)->i_ino, buf_obj->name ?: "NULL",
                   dma_buf_exp_pid(buf_obj), dma_buf_exp_task_comm(buf_obj) ?: "NULL");

        robj = buf_obj->resv;
        while (true) {
            seq = read_seqcount_begin(&robj->seq);
            rcu_read_lock();
            fobj = rcu_dereference(robj->fence);
            shared_count = fobj ? fobj->shared_count : 0;
            fence = rcu_dereference(robj->fence_excl);
            if (!read_seqcount_retry(&robj->seq, seq)) {
                break;
            }
            rcu_read_unlock();
        }

        if (fence) {
            seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n", fence->ops->get_driver_name(fence),
                       fence->ops->get_timeline_name(fence), dma_fence_is_signaled(fence) ? "" : "un");
        }
        for (i = 0; i < shared_count; i++) {
            fence = rcu_dereference(fobj->shared[i]);
            if (!dma_fence_get_rcu(fence)) {
                continue;
            }
            seq_printf(s, "\tShared fence: %s %s %ssignalled\n", fence->ops->get_driver_name(fence),
                       fence->ops->get_timeline_name(fence), dma_fence_is_signaled(fence) ? "" : "un");
            dma_fence_put(fence);
        }
        rcu_read_unlock();

        seq_puts(s, "\tAttached Devices:\n");
        attach_count = 0;

        list_for_each_entry(attach_obj, &buf_obj->attachments, node)
        {
            seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
            attach_count++;
        }
        dma_resv_unlock(buf_obj->resv);

        seq_printf(s, "Total %d devices attached\n\n", attach_count);

        count++;
        size += buf_obj->size;
    }

    seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);

    mutex_unlock(&db_list.lock);
    return 0;

error_unlock:
    mutex_unlock(&db_list.lock);
    return ret;
}

DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);

static struct dentry *dma_buf_debugfs_dir;

static int dma_buf_init_debugfs(void)
{
    struct dentry *d;
    int err = 0;

    d = debugfs_create_dir("dma_buf", NULL);
    if (IS_ERR(d)) {
        return PTR_ERR(d);
    }

    dma_buf_debugfs_dir = d;

    d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir, NULL, &dma_buf_debug_fops);
    if (IS_ERR(d)) {
        pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
        debugfs_remove_recursive(dma_buf_debugfs_dir);
        dma_buf_debugfs_dir = NULL;
        err = PTR_ERR(d);
    }

    dma_buf_process_info_init_debugfs(dma_buf_debugfs_dir);
    return err;
}

static void dma_buf_uninit_debugfs(void)
{
    debugfs_remove_recursive(dma_buf_debugfs_dir);
}
#else
static inline int dma_buf_init_debugfs(void)
{
    return 0;
}
static inline void dma_buf_uninit_debugfs(void)
{
}
#endif

#ifdef CONFIG_DMABUF_PROCESS_INFO
struct dma_buf *get_dma_buf_from_file(struct file *f)
{
    if (IS_ERR_OR_NULL(f)) {
        return NULL;
    }

    if (!is_dma_buf_file(f)) {
        return NULL;
    }

    return f->private_data;
}
#endif /* CONFIG_DMABUF_PROCESS_INFO */

static int __init dma_buf_init(void)
{
    int ret;

    ret = dma_buf_init_sysfs_statistics();
    if (ret) {
        return ret;
    }

    dma_buf_mnt = kern_mount(&dma_buf_fs_type);
    if (IS_ERR(dma_buf_mnt)) {
        return PTR_ERR(dma_buf_mnt);
    }

    mutex_init(&db_list.lock);
    INIT_LIST_HEAD(&db_list.head);
    dma_buf_init_debugfs();
    dma_buf_process_info_init_procfs();
    return 0;
}
subsys_initcall(dma_buf_init);

static void __exit dma_buf_deinit(void)
{
    dma_buf_uninit_debugfs();
    kern_unmount(dma_buf_mnt);
    dma_buf_uninit_sysfs_statistics();
    dma_buf_process_info_uninit_procfs();
}
__exitcall(dma_buf_deinit);