// SPDX-License-Identifier: GPL-2.0
/*
 *  file.c - part of debugfs, a tiny little debug file system
 *
 *  Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
 *  Copyright (C) 2004 IBM Inc.
 *
 *  debugfs is for people to use instead of /proc or /sys.
 *  See Documentation/filesystems/ for more details.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/pagemap.h>
#include <linux/debugfs.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/atomic.h>
#include <linux/device.h>
#include <linux/pm_runtime.h>
#include <linux/poll.h>
#include <linux/security.h>

#include "internal.h"

struct poll_table_struct;

static ssize_t default_read_file(struct file *file, char __user *buf,
                                 size_t count, loff_t *ppos)
{
        return 0;
}

static ssize_t default_write_file(struct file *file, const char __user *buf,
                                   size_t count, loff_t *ppos)
{
        return count;
}

const struct file_operations debugfs_noop_file_operations = {
        .read =         default_read_file,
        .write =        default_write_file,
        .open =         simple_open,
        .llseek =       noop_llseek,
};

#define F_DENTRY(filp) ((filp)->f_path.dentry)

void *debugfs_get_aux(const struct file *file)
{
        return DEBUGFS_I(file_inode(file))->aux;
}
EXPORT_SYMBOL_GPL(debugfs_get_aux);

enum dbgfs_get_mode {
        DBGFS_GET_ALREADY,
        DBGFS_GET_REGULAR,
        DBGFS_GET_SHORT,
};

static int __debugfs_file_get(struct dentry *dentry, enum dbgfs_get_mode mode)
{
        struct debugfs_fsdata *fsd;
        void *d_fsd;

        /*
         * This could only happen if some debugfs user erroneously calls
         * debugfs_file_get() on a dentry that isn't even a file, let
         * them know about it.
         */
        if (WARN_ON(!d_is_reg(dentry)))
                return -EINVAL;

        d_fsd = READ_ONCE(dentry->d_fsdata);
        if (d_fsd) {
                fsd = d_fsd;
        } else {
                struct inode *inode = dentry->d_inode;
                unsigned int methods = 0;

                if (WARN_ON(mode == DBGFS_GET_ALREADY))
                        return -EINVAL;

                fsd = kmalloc_obj(*fsd);
                if (!fsd)
                        return -ENOMEM;

                if (mode == DBGFS_GET_SHORT) {
                        const struct debugfs_short_fops *ops;
                        ops = fsd->short_fops = DEBUGFS_I(inode)->short_fops;
                        if (ops->llseek)
                                methods |= HAS_LSEEK;
                        if (ops->read)
                                methods |= HAS_READ;
                        if (ops->write)
                                methods |= HAS_WRITE;
                        fsd->real_fops = NULL;
                } else {
                        const struct file_operations *ops;
                        ops = fsd->real_fops = DEBUGFS_I(inode)->real_fops;
                        if (ops->llseek)
                                methods |= HAS_LSEEK;
                        if (ops->read)
                                methods |= HAS_READ;
                        if (ops->write)
                                methods |= HAS_WRITE;
                        if (ops->unlocked_ioctl)
                                methods |= HAS_IOCTL;
                        if (ops->poll)
                                methods |= HAS_POLL;
                        fsd->short_fops = NULL;
                }
                fsd->methods = methods;
                refcount_set(&fsd->active_users, 1);
                init_completion(&fsd->active_users_drained);
                INIT_LIST_HEAD(&fsd->cancellations);
                mutex_init(&fsd->cancellations_mtx);

                d_fsd = cmpxchg(&dentry->d_fsdata, NULL, fsd);
                if (d_fsd) {
                        mutex_destroy(&fsd->cancellations_mtx);
                        kfree(fsd);
                        fsd = d_fsd;
                }
        }

        /*
         * In case of a successful cmpxchg() above, this check is
         * strictly necessary and must follow it, see the comment in
         * __debugfs_remove_file().
         * OTOH, if the cmpxchg() hasn't been executed or wasn't
         * successful, this serves the purpose of not starving
         * removers.
         */
        if (d_unlinked(dentry))
                return -EIO;

        if (!refcount_inc_not_zero(&fsd->active_users))
                return -EIO;

        return 0;
}

/**
 * debugfs_file_get - mark the beginning of file data access
 * @dentry: the dentry object whose data is being accessed.
 *
 * Up to a matching call to debugfs_file_put(), any successive call
 * into the file removing functions debugfs_remove() and
 * debugfs_remove_recursive() will block. Since associated private
 * file data may only get freed after a successful return of any of
 * the removal functions, you may safely access it after a successful
 * call to debugfs_file_get() without worrying about lifetime issues.
 *
 * If -%EIO is returned, the file has already been removed and thus,
 * it is not safe to access any of its data. If, on the other hand,
 * it is allowed to access the file data, zero is returned.
 */
int debugfs_file_get(struct dentry *dentry)
{
        return __debugfs_file_get(dentry, DBGFS_GET_ALREADY);
}
EXPORT_SYMBOL_GPL(debugfs_file_get);

/**
 * debugfs_file_put - mark the end of file data access
 * @dentry: the dentry object formerly passed to
 *          debugfs_file_get().
 *
 * Allow any ongoing concurrent call into debugfs_remove() or
 * debugfs_remove_recursive() blocked by a former call to
 * debugfs_file_get() to proceed and return to its caller.
 */
void debugfs_file_put(struct dentry *dentry)
{
        struct debugfs_fsdata *fsd = READ_ONCE(dentry->d_fsdata);

        if (refcount_dec_and_test(&fsd->active_users))
                complete(&fsd->active_users_drained);
}
EXPORT_SYMBOL_GPL(debugfs_file_put);

/**
 * debugfs_enter_cancellation - enter a debugfs cancellation
 * @file: the file being accessed
 * @cancellation: the cancellation object, the cancel callback
 *      inside of it must be initialized
 *
 * When a debugfs file is removed it needs to wait for all active
 * operations to complete. However, the operation itself may need
 * to wait for hardware or completion of some asynchronous process
 * or similar. As such, it may need to be cancelled to avoid long
 * waits or even deadlocks.
 *
 * This function can be used inside a debugfs handler that may
 * need to be cancelled. As soon as this function is called, the
 * cancellation's 'cancel' callback may be called, at which point
 * the caller should proceed to call debugfs_leave_cancellation()
 * and leave the debugfs handler function as soon as possible.
 * Note that the 'cancel' callback is only ever called in the
 * context of some kind of debugfs_remove().
 *
 * This function must be paired with debugfs_leave_cancellation().
 */
void debugfs_enter_cancellation(struct file *file,
                                struct debugfs_cancellation *cancellation)
{
        struct debugfs_fsdata *fsd;
        struct dentry *dentry = F_DENTRY(file);

        INIT_LIST_HEAD(&cancellation->list);

        if (WARN_ON(!d_is_reg(dentry)))
                return;

        if (WARN_ON(!cancellation->cancel))
                return;

        fsd = READ_ONCE(dentry->d_fsdata);
        if (WARN_ON(!fsd))
                return;

        mutex_lock(&fsd->cancellations_mtx);
        list_add(&cancellation->list, &fsd->cancellations);
        mutex_unlock(&fsd->cancellations_mtx);

        /* if we're already removing wake it up to cancel */
        if (d_unlinked(dentry))
                complete(&fsd->active_users_drained);
}
EXPORT_SYMBOL_GPL(debugfs_enter_cancellation);

/**
 * debugfs_leave_cancellation - leave cancellation section
 * @file: the file being accessed
 * @cancellation: the cancellation previously registered with
 *      debugfs_enter_cancellation()
 *
 * See the documentation of debugfs_enter_cancellation().
 */
void debugfs_leave_cancellation(struct file *file,
                                struct debugfs_cancellation *cancellation)
{
        struct debugfs_fsdata *fsd;
        struct dentry *dentry = F_DENTRY(file);

        if (WARN_ON(!d_is_reg(dentry)))
                return;

        fsd = READ_ONCE(dentry->d_fsdata);
        if (WARN_ON(!fsd))
                return;

        mutex_lock(&fsd->cancellations_mtx);
        if (!list_empty(&cancellation->list))
                list_del(&cancellation->list);
        mutex_unlock(&fsd->cancellations_mtx);
}
EXPORT_SYMBOL_GPL(debugfs_leave_cancellation);

/*
 * Only permit access to world-readable files when the kernel is locked down.
 * We also need to exclude any file that has ways to write or alter it as root
 * can bypass the permissions check.
 */
static int debugfs_locked_down(struct inode *inode,
                               struct file *filp,
                               const struct file_operations *real_fops)
{
        if ((inode->i_mode & 07777 & ~0444) == 0 &&
            !(filp->f_mode & FMODE_WRITE) &&
            (!real_fops ||
             (!real_fops->unlocked_ioctl &&
              !real_fops->compat_ioctl &&
              !real_fops->mmap)))
                return 0;

        if (security_locked_down(LOCKDOWN_DEBUGFS))
                return -EPERM;

        return 0;
}

static int open_proxy_open(struct inode *inode, struct file *filp)
{
        struct dentry *dentry = F_DENTRY(filp);
        const struct file_operations *real_fops = DEBUGFS_I(inode)->real_fops;
        int r;

        r = __debugfs_file_get(dentry, DBGFS_GET_REGULAR);
        if (r)
                return r == -EIO ? -ENOENT : r;

        r = debugfs_locked_down(inode, filp, real_fops);
        if (r)
                goto out;

        if (!fops_get(real_fops)) {
#ifdef CONFIG_MODULES
                if (real_fops->owner &&
                    real_fops->owner->state == MODULE_STATE_GOING) {
                        r = -ENXIO;
                        goto out;
                }
#endif

                /* Huh? Module did not clean up after itself at exit? */
                WARN(1, "debugfs file owner did not clean up at exit: %pd",
                        dentry);
                r = -ENXIO;
                goto out;
        }
        replace_fops(filp, real_fops);

        if (real_fops->open)
                r = real_fops->open(inode, filp);

out:
        debugfs_file_put(dentry);
        return r;
}

const struct file_operations debugfs_open_proxy_file_operations = {
        .open = open_proxy_open,
};

#define PROTO(args...) args
#define ARGS(args...) args

#define FULL_PROXY_FUNC(name, ret_type, filp, proto, args, bit, ret)    \
static ret_type full_proxy_ ## name(proto)                              \
{                                                                       \
        struct dentry *dentry = F_DENTRY(filp);                         \
        struct debugfs_fsdata *fsd = dentry->d_fsdata;                  \
        ret_type r;                                                     \
                                                                        \
        if (!(fsd->methods & bit))                                      \
                return ret;                                             \
        r = debugfs_file_get(dentry);                                   \
        if (unlikely(r))                                                \
                return r;                                               \
        r = fsd->real_fops->name(args);                                 \
        debugfs_file_put(dentry);                                       \
        return r;                                                       \
}

#define SHORT_PROXY_FUNC(name, ret_type, filp, proto, args, bit, ret)   \
static ret_type short_proxy_ ## name(proto)                             \
{                                                                       \
        struct dentry *dentry = F_DENTRY(filp);                         \
        struct debugfs_fsdata *fsd = dentry->d_fsdata;                  \
        ret_type r;                                                     \
                                                                        \
        if (!(fsd->methods & bit))                                      \
                return ret;                                             \
        r = debugfs_file_get(dentry);                                   \
        if (unlikely(r))                                                \
                return r;                                               \
        r = fsd->short_fops->name(args);                                \
        debugfs_file_put(dentry);                                       \
        return r;                                                       \
}

SHORT_PROXY_FUNC(llseek, loff_t, filp,
                PROTO(struct file *filp, loff_t offset, int whence),
                ARGS(filp, offset, whence), HAS_LSEEK, -ESPIPE);

FULL_PROXY_FUNC(llseek, loff_t, filp,
                PROTO(struct file *filp, loff_t offset, int whence),
                ARGS(filp, offset, whence), HAS_LSEEK, -ESPIPE);

SHORT_PROXY_FUNC(read, ssize_t, filp,
                PROTO(struct file *filp, char __user *buf, size_t size,
                        loff_t *ppos),
                ARGS(filp, buf, size, ppos), HAS_READ, -EINVAL);

FULL_PROXY_FUNC(read, ssize_t, filp,
                PROTO(struct file *filp, char __user *buf, size_t size,
                        loff_t *ppos),
                ARGS(filp, buf, size, ppos), HAS_READ, -EINVAL);

SHORT_PROXY_FUNC(write, ssize_t, filp,
                PROTO(struct file *filp, const char __user *buf,
                        size_t size, loff_t *ppos),
                ARGS(filp, buf, size, ppos), HAS_WRITE, -EINVAL);

FULL_PROXY_FUNC(write, ssize_t, filp,
                PROTO(struct file *filp, const char __user *buf,
                        size_t size, loff_t *ppos),
                ARGS(filp, buf, size, ppos), HAS_WRITE, -EINVAL);

FULL_PROXY_FUNC(unlocked_ioctl, long, filp,
                PROTO(struct file *filp, unsigned int cmd, unsigned long arg),
                ARGS(filp, cmd, arg), HAS_IOCTL, -ENOTTY);

static __poll_t full_proxy_poll(struct file *filp,
                                struct poll_table_struct *wait)
{
        struct dentry *dentry = F_DENTRY(filp);
        struct debugfs_fsdata *fsd = dentry->d_fsdata;
        __poll_t r = 0;

        if (!(fsd->methods & HAS_POLL))
                return DEFAULT_POLLMASK;
        if (debugfs_file_get(dentry))
                return EPOLLHUP;

        r = fsd->real_fops->poll(filp, wait);
        debugfs_file_put(dentry);
        return r;
}

static int full_proxy_release(struct inode *inode, struct file *file)
{
        struct debugfs_fsdata *fsd = F_DENTRY(file)->d_fsdata;
        const struct file_operations *real_fops = fsd->real_fops;
        int r = 0;

        /*
         * We must not protect this against removal races here: the
         * original releaser should be called unconditionally in order
         * not to leak any resources. Releasers must not assume that
         * ->i_private is still being meaningful here.
         */
        if (real_fops->release)
                r = real_fops->release(inode, file);

        fops_put(real_fops);
        return r;
}

static int full_proxy_open_regular(struct inode *inode, struct file *filp)
{
        struct dentry *dentry = F_DENTRY(filp);
        const struct file_operations *real_fops;
        struct debugfs_fsdata *fsd;
        int r;

        r = __debugfs_file_get(dentry, DBGFS_GET_REGULAR);
        if (r)
                return r == -EIO ? -ENOENT : r;

        fsd = dentry->d_fsdata;
        real_fops = fsd->real_fops;
        r = debugfs_locked_down(inode, filp, real_fops);
        if (r)
                goto out;

        if (!fops_get(real_fops)) {
#ifdef CONFIG_MODULES
                if (real_fops->owner &&
                    real_fops->owner->state == MODULE_STATE_GOING) {
                        r = -ENXIO;
                        goto out;
                }
#endif

                /* Huh? Module did not cleanup after itself at exit? */
                WARN(1, "debugfs file owner did not clean up at exit: %pd",
                        dentry);
                r = -ENXIO;
                goto out;
        }

        if (real_fops->open) {
                r = real_fops->open(inode, filp);
                if (r) {
                        fops_put(real_fops);
                } else if (filp->f_op != &debugfs_full_proxy_file_operations) {
                        /* No protection against file removal anymore. */
                        WARN(1, "debugfs file owner replaced proxy fops: %pd",
                                dentry);
                        fops_put(real_fops);
                }
        }
out:
        debugfs_file_put(dentry);
        return r;
}

const struct file_operations debugfs_full_proxy_file_operations = {
        .open = full_proxy_open_regular,
        .release = full_proxy_release,
        .llseek = full_proxy_llseek,
        .read = full_proxy_read,
        .write = full_proxy_write,
        .poll = full_proxy_poll,
        .unlocked_ioctl = full_proxy_unlocked_ioctl
};

static int full_proxy_open_short(struct inode *inode, struct file *filp)
{
        struct dentry *dentry = F_DENTRY(filp);
        int r;

        r = __debugfs_file_get(dentry, DBGFS_GET_SHORT);
        if (r)
                return r == -EIO ? -ENOENT : r;
        r = debugfs_locked_down(inode, filp, NULL);
        if (!r)
                r = simple_open(inode, filp);
        debugfs_file_put(dentry);
        return r;
}

const struct file_operations debugfs_full_short_proxy_file_operations = {
        .open = full_proxy_open_short,
        .llseek = short_proxy_llseek,
        .read = short_proxy_read,
        .write = short_proxy_write,
};

ssize_t debugfs_attr_read(struct file *file, char __user *buf,
                        size_t len, loff_t *ppos)
{
        struct dentry *dentry = F_DENTRY(file);
        ssize_t ret;

        ret = debugfs_file_get(dentry);
        if (unlikely(ret))
                return ret;
        ret = simple_attr_read(file, buf, len, ppos);
        debugfs_file_put(dentry);
        return ret;
}
EXPORT_SYMBOL_GPL(debugfs_attr_read);

static ssize_t debugfs_attr_write_xsigned(struct file *file, const char __user *buf,
                         size_t len, loff_t *ppos, bool is_signed)
{
        struct dentry *dentry = F_DENTRY(file);
        ssize_t ret;

        ret = debugfs_file_get(dentry);
        if (unlikely(ret))
                return ret;
        if (is_signed)
                ret = simple_attr_write_signed(file, buf, len, ppos);
        else
                ret = simple_attr_write(file, buf, len, ppos);
        debugfs_file_put(dentry);
        return ret;
}

ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
                         size_t len, loff_t *ppos)
{
        return debugfs_attr_write_xsigned(file, buf, len, ppos, false);
}
EXPORT_SYMBOL_GPL(debugfs_attr_write);

ssize_t debugfs_attr_write_signed(struct file *file, const char __user *buf,
                         size_t len, loff_t *ppos)
{
        return debugfs_attr_write_xsigned(file, buf, len, ppos, true);
}
EXPORT_SYMBOL_GPL(debugfs_attr_write_signed);

static struct dentry *debugfs_create_mode_unsafe(const char *name, umode_t mode,
                                        struct dentry *parent, void *value,
                                        const struct file_operations *fops,
                                        const struct file_operations *fops_ro,
                                        const struct file_operations *fops_wo)
{
        /* if there are no write bits set, make read only */
        if (!(mode & S_IWUGO))
                return debugfs_create_file_unsafe(name, mode, parent, value,
                                                fops_ro);
        /* if there are no read bits set, make write only */
        if (!(mode & S_IRUGO))
                return debugfs_create_file_unsafe(name, mode, parent, value,
                                                fops_wo);

        return debugfs_create_file_unsafe(name, mode, parent, value, fops);
}

static int debugfs_u8_set(void *data, u64 val)
{
        *(u8 *)data = val;
        return 0;
}
static int debugfs_u8_get(void *data, u64 *val)
{
        *val = *(u8 *)data;
        return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_u8, debugfs_u8_get, debugfs_u8_set, "%llu\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_u8_ro, debugfs_u8_get, NULL, "%llu\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_u8_wo, NULL, debugfs_u8_set, "%llu\n");

/**
 * debugfs_create_u8 - create a debugfs file that is used to read and write an unsigned 8-bit value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 *
 * This function creates a file in debugfs with the given name that
 * contains the value of the variable @value.  If the @mode variable is so
 * set, it can be read from, and written to.
 */
void debugfs_create_u8(const char *name, umode_t mode, struct dentry *parent,
                       u8 *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_u8,
                                   &fops_u8_ro, &fops_u8_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_u8);

static int debugfs_u16_set(void *data, u64 val)
{
        *(u16 *)data = val;
        return 0;
}
static int debugfs_u16_get(void *data, u64 *val)
{
        *val = *(u16 *)data;
        return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_u16, debugfs_u16_get, debugfs_u16_set, "%llu\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_u16_ro, debugfs_u16_get, NULL, "%llu\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_u16_wo, NULL, debugfs_u16_set, "%llu\n");

/**
 * debugfs_create_u16 - create a debugfs file that is used to read and write an unsigned 16-bit value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 *
 * This function creates a file in debugfs with the given name that
 * contains the value of the variable @value.  If the @mode variable is so
 * set, it can be read from, and written to.
 */
void debugfs_create_u16(const char *name, umode_t mode, struct dentry *parent,
                        u16 *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_u16,
                                   &fops_u16_ro, &fops_u16_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_u16);

static int debugfs_u32_set(void *data, u64 val)
{
        *(u32 *)data = val;
        return 0;
}
static int debugfs_u32_get(void *data, u64 *val)
{
        *val = *(u32 *)data;
        return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_u32, debugfs_u32_get, debugfs_u32_set, "%llu\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_u32_ro, debugfs_u32_get, NULL, "%llu\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_u32_wo, NULL, debugfs_u32_set, "%llu\n");

/**
 * debugfs_create_u32 - create a debugfs file that is used to read and write an unsigned 32-bit value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 *
 * This function creates a file in debugfs with the given name that
 * contains the value of the variable @value.  If the @mode variable is so
 * set, it can be read from, and written to.
 */
void debugfs_create_u32(const char *name, umode_t mode, struct dentry *parent,
                        u32 *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_u32,
                                   &fops_u32_ro, &fops_u32_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_u32);

static int debugfs_u64_set(void *data, u64 val)
{
        *(u64 *)data = val;
        return 0;
}

static int debugfs_u64_get(void *data, u64 *val)
{
        *val = *(u64 *)data;
        return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_u64, debugfs_u64_get, debugfs_u64_set, "%llu\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_u64_ro, debugfs_u64_get, NULL, "%llu\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_u64_wo, NULL, debugfs_u64_set, "%llu\n");

/**
 * debugfs_create_u64 - create a debugfs file that is used to read and write an unsigned 64-bit value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 *
 * This function creates a file in debugfs with the given name that
 * contains the value of the variable @value.  If the @mode variable is so
 * set, it can be read from, and written to.
 */
void debugfs_create_u64(const char *name, umode_t mode, struct dentry *parent,
                        u64 *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_u64,
                                   &fops_u64_ro, &fops_u64_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_u64);

static int debugfs_ulong_set(void *data, u64 val)
{
        *(unsigned long *)data = val;
        return 0;
}

static int debugfs_ulong_get(void *data, u64 *val)
{
        *val = *(unsigned long *)data;
        return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_ulong, debugfs_ulong_get, debugfs_ulong_set,
                        "%llu\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_ulong_ro, debugfs_ulong_get, NULL, "%llu\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_ulong_wo, NULL, debugfs_ulong_set, "%llu\n");

/**
 * debugfs_create_ulong - create a debugfs file that is used to read and write
 * an unsigned long value.
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 *
 * This function creates a file in debugfs with the given name that
 * contains the value of the variable @value.  If the @mode variable is so
 * set, it can be read from, and written to.
 */
void debugfs_create_ulong(const char *name, umode_t mode, struct dentry *parent,
                          unsigned long *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_ulong,
                                   &fops_ulong_ro, &fops_ulong_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_ulong);

DEFINE_DEBUGFS_ATTRIBUTE(fops_x8, debugfs_u8_get, debugfs_u8_set, "0x%02llx\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_x8_ro, debugfs_u8_get, NULL, "0x%02llx\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_x8_wo, NULL, debugfs_u8_set, "0x%02llx\n");

DEFINE_DEBUGFS_ATTRIBUTE(fops_x16, debugfs_u16_get, debugfs_u16_set,
                        "0x%04llx\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_x16_ro, debugfs_u16_get, NULL, "0x%04llx\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_x16_wo, NULL, debugfs_u16_set, "0x%04llx\n");

DEFINE_DEBUGFS_ATTRIBUTE(fops_x32, debugfs_u32_get, debugfs_u32_set,
                        "0x%08llx\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_x32_ro, debugfs_u32_get, NULL, "0x%08llx\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_x32_wo, NULL, debugfs_u32_set, "0x%08llx\n");

DEFINE_DEBUGFS_ATTRIBUTE(fops_x64, debugfs_u64_get, debugfs_u64_set,
                        "0x%016llx\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_x64_ro, debugfs_u64_get, NULL, "0x%016llx\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_x64_wo, NULL, debugfs_u64_set, "0x%016llx\n");

/*
 * debugfs_create_x{8,16,32,64} - create a debugfs file that is used to read and write an unsigned {8,16,32,64}-bit value
 *
 * These functions are exactly the same as the above functions (but use a hex
 * output for the decimal challenged). For details look at the above unsigned
 * decimal functions.
 */

/**
 * debugfs_create_x8 - create a debugfs file that is used to read and write an unsigned 8-bit value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 */
void debugfs_create_x8(const char *name, umode_t mode, struct dentry *parent,
                       u8 *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_x8,
                                   &fops_x8_ro, &fops_x8_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_x8);

/**
 * debugfs_create_x16 - create a debugfs file that is used to read and write an unsigned 16-bit value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 */
void debugfs_create_x16(const char *name, umode_t mode, struct dentry *parent,
                        u16 *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_x16,
                                   &fops_x16_ro, &fops_x16_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_x16);

/**
 * debugfs_create_x32 - create a debugfs file that is used to read and write an unsigned 32-bit value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 */
void debugfs_create_x32(const char *name, umode_t mode, struct dentry *parent,
                        u32 *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_x32,
                                   &fops_x32_ro, &fops_x32_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_x32);

/**
 * debugfs_create_x64 - create a debugfs file that is used to read and write an unsigned 64-bit value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 */
void debugfs_create_x64(const char *name, umode_t mode, struct dentry *parent,
                        u64 *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_x64,
                                   &fops_x64_ro, &fops_x64_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_x64);


static int debugfs_size_t_set(void *data, u64 val)
{
        *(size_t *)data = val;
        return 0;
}
static int debugfs_size_t_get(void *data, u64 *val)
{
        *val = *(size_t *)data;
        return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_size_t, debugfs_size_t_get, debugfs_size_t_set,
                        "%llu\n"); /* %llu and %zu are more or less the same */
DEFINE_DEBUGFS_ATTRIBUTE(fops_size_t_ro, debugfs_size_t_get, NULL, "%llu\n");
DEFINE_DEBUGFS_ATTRIBUTE(fops_size_t_wo, NULL, debugfs_size_t_set, "%llu\n");

/**
 * debugfs_create_size_t - create a debugfs file that is used to read and write an size_t value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 */
void debugfs_create_size_t(const char *name, umode_t mode,
                           struct dentry *parent, size_t *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_size_t,
                                   &fops_size_t_ro, &fops_size_t_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_size_t);

static int debugfs_atomic_t_set(void *data, u64 val)
{
        atomic_set((atomic_t *)data, val);
        return 0;
}
static int debugfs_atomic_t_get(void *data, u64 *val)
{
        *val = atomic_read((atomic_t *)data);
        return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE_SIGNED(fops_atomic_t, debugfs_atomic_t_get,
                        debugfs_atomic_t_set, "%lld\n");
DEFINE_DEBUGFS_ATTRIBUTE_SIGNED(fops_atomic_t_ro, debugfs_atomic_t_get, NULL,
                        "%lld\n");
DEFINE_DEBUGFS_ATTRIBUTE_SIGNED(fops_atomic_t_wo, NULL, debugfs_atomic_t_set,
                        "%lld\n");

/**
 * debugfs_create_atomic_t - create a debugfs file that is used to read and
 * write an atomic_t value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 */
void debugfs_create_atomic_t(const char *name, umode_t mode,
                             struct dentry *parent, atomic_t *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_atomic_t,
                                   &fops_atomic_t_ro, &fops_atomic_t_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_atomic_t);

ssize_t debugfs_read_file_bool(struct file *file, char __user *user_buf,
                               size_t count, loff_t *ppos)
{
        char buf[2];
        bool val;
        int r;
        struct dentry *dentry = F_DENTRY(file);

        r = debugfs_file_get(dentry);
        if (unlikely(r))
                return r;
        val = *(bool *)file->private_data;
        debugfs_file_put(dentry);

        if (val)
                buf[0] = 'Y';
        else
                buf[0] = 'N';
        buf[1] = '\n';
        return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
}
EXPORT_SYMBOL_GPL(debugfs_read_file_bool);

ssize_t debugfs_write_file_bool(struct file *file, const char __user *user_buf,
                                size_t count, loff_t *ppos)
{
        bool bv;
        int r;
        bool *val = file->private_data;
        struct dentry *dentry = F_DENTRY(file);

        r = kstrtobool_from_user(user_buf, count, &bv);
        if (!r) {
                r = debugfs_file_get(dentry);
                if (unlikely(r))
                        return r;
                *val = bv;
                debugfs_file_put(dentry);
        }

        return count;
}
EXPORT_SYMBOL_GPL(debugfs_write_file_bool);

static const struct file_operations fops_bool = {
        .read =         debugfs_read_file_bool,
        .write =        debugfs_write_file_bool,
        .open =         simple_open,
        .llseek =       default_llseek,
};

static const struct file_operations fops_bool_ro = {
        .read =         debugfs_read_file_bool,
        .open =         simple_open,
        .llseek =       default_llseek,
};

static const struct file_operations fops_bool_wo = {
        .write =        debugfs_write_file_bool,
        .open =         simple_open,
        .llseek =       default_llseek,
};

/**
 * debugfs_create_bool - create a debugfs file that is used to read and write a boolean value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 *
 * This function creates a file in debugfs with the given name that
 * contains the value of the variable @value.  If the @mode variable is so
 * set, it can be read from, and written to.
 */
void debugfs_create_bool(const char *name, umode_t mode, struct dentry *parent,
                         bool *value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_bool,
                                   &fops_bool_ro, &fops_bool_wo);
}
EXPORT_SYMBOL_GPL(debugfs_create_bool);

ssize_t debugfs_read_file_str(struct file *file, char __user *user_buf,
                              size_t count, loff_t *ppos)
{
        struct dentry *dentry = F_DENTRY(file);
        char *str, *copy = NULL;
        int copy_len, len;
        ssize_t ret;

        ret = debugfs_file_get(dentry);
        if (unlikely(ret))
                return ret;

        str = *(char **)file->private_data;
        len = strlen(str) + 1;
        copy = kmalloc(len, GFP_KERNEL);
        if (!copy) {
                debugfs_file_put(dentry);
                return -ENOMEM;
        }

        copy_len = strscpy(copy, str, len);
        debugfs_file_put(dentry);
        if (copy_len < 0) {
                kfree(copy);
                return copy_len;
        }

        copy[copy_len] = '\n';

        ret = simple_read_from_buffer(user_buf, count, ppos, copy, len);
        kfree(copy);

        return ret;
}
EXPORT_SYMBOL_GPL(debugfs_create_str);

static ssize_t debugfs_write_file_str(struct file *file, const char __user *user_buf,
                                      size_t count, loff_t *ppos)
{
        struct dentry *dentry = F_DENTRY(file);
        char *old, *new = NULL;
        int pos = *ppos;
        int r;

        r = debugfs_file_get(dentry);
        if (unlikely(r))
                return r;

        old = *(char **)file->private_data;

        /* only allow strict concatenation */
        r = -EINVAL;
        if (pos && pos != strlen(old))
                goto error;

        r = -E2BIG;
        if (pos + count + 1 > PAGE_SIZE)
                goto error;

        r = -ENOMEM;
        new = kmalloc(pos + count + 1, GFP_KERNEL);
        if (!new)
                goto error;

        if (pos)
                memcpy(new, old, pos);

        r = -EFAULT;
        if (copy_from_user(new + pos, user_buf, count))
                goto error;

        new[pos + count] = '\0';
        strim(new);

        rcu_assign_pointer(*(char __rcu **)file->private_data, new);
        synchronize_rcu();
        kfree(old);

        debugfs_file_put(dentry);
        return count;

error:
        kfree(new);
        debugfs_file_put(dentry);
        return r;
}

static const struct file_operations fops_str = {
        .read =         debugfs_read_file_str,
        .write =        debugfs_write_file_str,
        .open =         simple_open,
        .llseek =       default_llseek,
};

static const struct file_operations fops_str_ro = {
        .read =         debugfs_read_file_str,
        .open =         simple_open,
        .llseek =       default_llseek,
};

static const struct file_operations fops_str_wo = {
        .write =        debugfs_write_file_str,
        .open =         simple_open,
        .llseek =       default_llseek,
};

/**
 * debugfs_create_str - create a debugfs file that is used to read and write a string value
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @value: a pointer to the variable that the file should read to and write
 *         from.
 *
 * This function creates a file in debugfs with the given name that
 * contains the value of the variable @value.  If the @mode variable is so
 * set, it can be read from, and written to.
 */
void debugfs_create_str(const char *name, umode_t mode,
                        struct dentry *parent, char **value)
{
        debugfs_create_mode_unsafe(name, mode, parent, value, &fops_str,
                                   &fops_str_ro, &fops_str_wo);
}

static ssize_t read_file_blob(struct file *file, char __user *user_buf,
                              size_t count, loff_t *ppos)
{
        struct debugfs_blob_wrapper *blob = file->private_data;
        struct dentry *dentry = F_DENTRY(file);
        ssize_t r;

        r = debugfs_file_get(dentry);
        if (unlikely(r))
                return r;
        r = simple_read_from_buffer(user_buf, count, ppos, blob->data,
                                blob->size);
        debugfs_file_put(dentry);
        return r;
}

static ssize_t write_file_blob(struct file *file, const char __user *user_buf,
                               size_t count, loff_t *ppos)
{
        struct debugfs_blob_wrapper *blob = file->private_data;
        struct dentry *dentry = F_DENTRY(file);
        ssize_t r;

        r = debugfs_file_get(dentry);
        if (unlikely(r))
                return r;
        r = simple_write_to_buffer(blob->data, blob->size, ppos, user_buf,
                                   count);

        debugfs_file_put(dentry);
        return r;
}

static const struct file_operations fops_blob = {
        .read =         read_file_blob,
        .write =        write_file_blob,
        .open =         simple_open,
        .llseek =       default_llseek,
};

/**
 * debugfs_create_blob - create a debugfs file that is used to read and write
 * a binary blob
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @blob: a pointer to a struct debugfs_blob_wrapper which contains a pointer
 *        to the blob data and the size of the data.
 *
 * This function creates a file in debugfs with the given name that exports
 * @blob->data as a binary blob. If the @mode variable is so set it can be
 * read from and written to.
 *
 * This function will return a pointer to a dentry if it succeeds.  This
 * pointer must be passed to the debugfs_remove() function when the file is
 * to be removed (no automatic cleanup happens if your module is unloaded,
 * you are responsible here.)  If an error occurs, ERR_PTR(-ERROR) will be
 * returned.
 *
 * If debugfs is not enabled in the kernel, the value ERR_PTR(-ENODEV) will
 * be returned.
 */
struct dentry *debugfs_create_blob(const char *name, umode_t mode,
                                   struct dentry *parent,
                                   struct debugfs_blob_wrapper *blob)
{
        return debugfs_create_file_unsafe(name, mode & 0644, parent, blob, &fops_blob);
}
EXPORT_SYMBOL_GPL(debugfs_create_blob);

static size_t u32_format_array(char *buf, size_t bufsize,
                               u32 *array, int array_size)
{
        size_t ret = 0;

        while (--array_size >= 0) {
                size_t len;
                char term = array_size ? ' ' : '\n';

                len = snprintf(buf, bufsize, "%u%c", *array++, term);
                ret += len;

                buf += len;
                bufsize -= len;
        }
        return ret;
}

static int u32_array_open(struct inode *inode, struct file *file)
{
        struct debugfs_u32_array *data = inode->i_private;
        int size, elements = data->n_elements;
        char *buf;

        /*
         * Max size:
         *  - 10 digits + ' '/'\n' = 11 bytes per number
         *  - terminating NUL character
         */
        size = elements*11;
        buf = kmalloc(size+1, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;
        buf[size] = 0;

        file->private_data = buf;
        u32_format_array(buf, size, data->array, data->n_elements);

        return nonseekable_open(inode, file);
}

static ssize_t u32_array_read(struct file *file, char __user *buf, size_t len,
                              loff_t *ppos)
{
        size_t size = strlen(file->private_data);

        return simple_read_from_buffer(buf, len, ppos,
                                        file->private_data, size);
}

static int u32_array_release(struct inode *inode, struct file *file)
{
        kfree(file->private_data);

        return 0;
}

static const struct file_operations u32_array_fops = {
        .owner   = THIS_MODULE,
        .open    = u32_array_open,
        .release = u32_array_release,
        .read    = u32_array_read,
};

/**
 * debugfs_create_u32_array - create a debugfs file that is used to read u32
 * array.
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have.
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @array: wrapper struct containing data pointer and size of the array.
 *
 * This function creates a file in debugfs with the given name that exports
 * @array as data. If the @mode variable is so set it can be read from.
 * Writing is not supported. Seek within the file is also not supported.
 * Once array is created its size can not be changed.
 */
void debugfs_create_u32_array(const char *name, umode_t mode,
                              struct dentry *parent,
                              struct debugfs_u32_array *array)
{
        debugfs_create_file_unsafe(name, mode, parent, array, &u32_array_fops);
}
EXPORT_SYMBOL_GPL(debugfs_create_u32_array);

#ifdef CONFIG_HAS_IOMEM

/*
 * The regset32 stuff is used to print 32-bit registers using the
 * seq_file utilities. We offer printing a register set in an already-opened
 * sequential file or create a debugfs file that only prints a regset32.
 */

/**
 * debugfs_print_regs32 - use seq_print to describe a set of registers
 * @s: the seq_file structure being used to generate output
 * @regs: an array if struct debugfs_reg32 structures
 * @nregs: the length of the above array
 * @base: the base address to be used in reading the registers
 * @prefix: a string to be prefixed to every output line
 *
 * This function outputs a text block describing the current values of
 * some 32-bit hardware registers. It is meant to be used within debugfs
 * files based on seq_file that need to show registers, intermixed with other
 * information. The prefix argument may be used to specify a leading string,
 * because some peripherals have several blocks of identical registers,
 * for example configuration of dma channels
 */
void debugfs_print_regs32(struct seq_file *s, const struct debugfs_reg32 *regs,
                          int nregs, void __iomem *base, char *prefix)
{
        int i;

        for (i = 0; i < nregs; i++, regs++) {
                if (prefix)
                        seq_printf(s, "%s", prefix);
                seq_printf(s, "%s = 0x%08x\n", regs->name,
                           readl(base + regs->offset));
                if (seq_has_overflowed(s))
                        break;
        }
}
EXPORT_SYMBOL_GPL(debugfs_print_regs32);

static int debugfs_regset32_show(struct seq_file *s, void *data)
{
        struct debugfs_regset32 *regset = s->private;

        if (regset->dev)
                pm_runtime_get_sync(regset->dev);

        debugfs_print_regs32(s, regset->regs, regset->nregs, regset->base, "");

        if (regset->dev)
                pm_runtime_put(regset->dev);

        return 0;
}

DEFINE_SHOW_ATTRIBUTE(debugfs_regset32);

/**
 * debugfs_create_regset32 - create a debugfs file that returns register values
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is %NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @regset: a pointer to a struct debugfs_regset32, which contains a pointer
 *          to an array of register definitions, the array size and the base
 *          address where the register bank is to be found.
 *
 * This function creates a file in debugfs with the given name that reports
 * the names and values of a set of 32-bit registers. If the @mode variable
 * is so set it can be read from. Writing is not supported.
 */
void debugfs_create_regset32(const char *name, umode_t mode,
                             struct dentry *parent,
                             struct debugfs_regset32 *regset)
{
        debugfs_create_file(name, mode, parent, regset, &debugfs_regset32_fops);
}
EXPORT_SYMBOL_GPL(debugfs_create_regset32);

#endif /* CONFIG_HAS_IOMEM */

struct debugfs_devm_entry {
        int (*read)(struct seq_file *seq, void *data);
        struct device *dev;
};

static int debugfs_devm_entry_open(struct inode *inode, struct file *f)
{
        struct debugfs_devm_entry *entry = inode->i_private;

        return single_open(f, entry->read, entry->dev);
}

static const struct file_operations debugfs_devm_entry_ops = {
        .owner = THIS_MODULE,
        .open = debugfs_devm_entry_open,
        .release = single_release,
        .read = seq_read,
        .llseek = seq_lseek
};

/**
 * debugfs_create_devm_seqfile - create a debugfs file that is bound to device.
 *
 * @dev: device related to this debugfs file.
 * @name: name of the debugfs file.
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *      directory dentry if set.  If this parameter is %NULL, then the
 *      file will be created in the root of the debugfs filesystem.
 * @read_fn: function pointer called to print the seq_file content.
 */
void debugfs_create_devm_seqfile(struct device *dev, const char *name,
                                 struct dentry *parent,
                                 int (*read_fn)(struct seq_file *s, void *data))
{
        struct debugfs_devm_entry *entry;

        if (IS_ERR(parent))
                return;

        entry = devm_kzalloc(dev, sizeof(*entry), GFP_KERNEL);
        if (!entry)
                return;

        entry->read = read_fn;
        entry->dev = dev;

        debugfs_create_file(name, S_IRUGO, parent, entry,
                            &debugfs_devm_entry_ops);
}
EXPORT_SYMBOL_GPL(debugfs_create_devm_seqfile);