/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * configfs.h - definitions for the device driver filesystem
 *
 * Based on sysfs:
 *      sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
 *
 * Based on kobject.h:
 *      Copyright (c) 2002-2003 Patrick Mochel
 *      Copyright (c) 2002-2003 Open Source Development Labs
 *
 * configfs Copyright (C) 2005 Oracle.  All rights reserved.
 *
 * Please read Documentation/filesystems/configfs.rst before using
 * the configfs interface, ESPECIALLY the parts about reference counts and
 * item destructors.
 */

#ifndef _CONFIGFS_H_
#define _CONFIGFS_H_

#include <linux/stat.h>   /* S_IRUGO */
#include <linux/types.h>  /* ssize_t */
#include <linux/list.h>   /* struct list_head */
#include <linux/kref.h>   /* struct kref */
#include <linux/mutex.h>  /* struct mutex */

#define CONFIGFS_ITEM_NAME_LEN  20

struct module;

struct configfs_item_operations;
struct configfs_group_operations;
struct configfs_attribute;
struct configfs_bin_attribute;
struct configfs_subsystem;

struct config_item {
        char                    *ci_name;
        char                    ci_namebuf[CONFIGFS_ITEM_NAME_LEN];
        struct kref             ci_kref;
        struct list_head        ci_entry;
        struct config_item      *ci_parent;
        struct config_group     *ci_group;
        const struct config_item_type   *ci_type;
        struct dentry           *ci_dentry;
};

extern __printf(2, 3)
int config_item_set_name(struct config_item *, const char *, ...);

static inline char *config_item_name(struct config_item * item)
{
        return item->ci_name;
}

extern void config_item_init_type_name(struct config_item *item,
                                       const char *name,
                                       const struct config_item_type *type);

extern struct config_item *config_item_get(struct config_item *);
extern struct config_item *config_item_get_unless_zero(struct config_item *);
extern void config_item_put(struct config_item *);

struct config_item_type {
        struct module                           *ct_owner;
        const struct configfs_item_operations   *ct_item_ops;
        const struct configfs_group_operations  *ct_group_ops;
        struct configfs_attribute               **ct_attrs;
        struct configfs_bin_attribute           **ct_bin_attrs;
};

/**
 *      group - a group of config_items of a specific type, belonging
 *      to a specific subsystem.
 */
struct config_group {
        struct config_item              cg_item;
        struct list_head                cg_children;
        struct configfs_subsystem       *cg_subsys;
        struct list_head                default_groups;
        struct list_head                group_entry;
};

extern void config_group_init(struct config_group *group);
extern void config_group_init_type_name(struct config_group *group,
                                        const char *name,
                                        const struct config_item_type *type);

static inline struct config_group *to_config_group(struct config_item *item)
{
        return item ? container_of(item,struct config_group,cg_item) : NULL;
}

static inline struct config_group *config_group_get(struct config_group *group)
{
        return group ? to_config_group(config_item_get(&group->cg_item)) : NULL;
}

static inline void config_group_put(struct config_group *group)
{
        config_item_put(&group->cg_item);
}

extern struct config_item *config_group_find_item(struct config_group *,
                                                  const char *);


static inline void configfs_add_default_group(struct config_group *new_group,
                struct config_group *group)
{
        list_add_tail(&new_group->group_entry, &group->default_groups);
}

struct configfs_attribute {
        const char              *ca_name;
        struct module           *ca_owner;
        umode_t                 ca_mode;
        ssize_t (*show)(struct config_item *, char *);
        ssize_t (*store)(struct config_item *, const char *, size_t);
};

#define CONFIGFS_ATTR_PERM(_pfx, _name, _perm)          \
static struct configfs_attribute _pfx##attr_##_name = { \
        .ca_name        = __stringify(_name),           \
        .ca_mode        = _perm,                        \
        .ca_owner       = THIS_MODULE,                  \
        .show           = _pfx##_name##_show,           \
        .store          = _pfx##_name##_store,          \
}

#define CONFIGFS_ATTR(_pfx, _name) CONFIGFS_ATTR_PERM(  \
                _pfx, _name, S_IRUGO | S_IWUSR          \
)

#define CONFIGFS_ATTR_RO(_pfx, _name)                   \
static struct configfs_attribute _pfx##attr_##_name = { \
        .ca_name        = __stringify(_name),           \
        .ca_mode        = S_IRUGO,                      \
        .ca_owner       = THIS_MODULE,                  \
        .show           = _pfx##_name##_show,           \
}

#define CONFIGFS_ATTR_WO(_pfx, _name)                   \
static struct configfs_attribute _pfx##attr_##_name = { \
        .ca_name        = __stringify(_name),           \
        .ca_mode        = S_IWUSR,                      \
        .ca_owner       = THIS_MODULE,                  \
        .store          = _pfx##_name##_store,          \
}

struct file;
struct vm_area_struct;

struct configfs_bin_attribute {
        struct configfs_attribute cb_attr;      /* std. attribute */
        void *cb_private;                       /* for user       */
        size_t cb_max_size;                     /* max core size  */
        ssize_t (*read)(struct config_item *, void *, size_t);
        ssize_t (*write)(struct config_item *, const void *, size_t);
};

#define CONFIGFS_BIN_ATTR(_pfx, _name, _priv, _maxsz)           \
static struct configfs_bin_attribute _pfx##attr_##_name = {     \
        .cb_attr = {                                            \
                .ca_name        = __stringify(_name),           \
                .ca_mode        = S_IRUGO | S_IWUSR,            \
                .ca_owner       = THIS_MODULE,                  \
        },                                                      \
        .cb_private     = _priv,                                \
        .cb_max_size    = _maxsz,                               \
        .read           = _pfx##_name##_read,                   \
        .write          = _pfx##_name##_write,                  \
}

#define CONFIGFS_BIN_ATTR_RO(_pfx, _name, _priv, _maxsz)        \
static struct configfs_bin_attribute _pfx##attr_##_name = {     \
        .cb_attr = {                                            \
                .ca_name        = __stringify(_name),           \
                .ca_mode        = S_IRUGO,                      \
                .ca_owner       = THIS_MODULE,                  \
        },                                                      \
        .cb_private     = _priv,                                \
        .cb_max_size    = _maxsz,                               \
        .read           = _pfx##_name##_read,                   \
}

#define CONFIGFS_BIN_ATTR_WO(_pfx, _name, _priv, _maxsz)        \
static struct configfs_bin_attribute _pfx##attr_##_name = {     \
        .cb_attr = {                                            \
                .ca_name        = __stringify(_name),           \
                .ca_mode        = S_IWUSR,                      \
                .ca_owner       = THIS_MODULE,                  \
        },                                                      \
        .cb_private     = _priv,                                \
        .cb_max_size    = _maxsz,                               \
        .write          = _pfx##_name##_write,                  \
}

/*
 * If allow_link() exists, the item can symlink(2) out to other
 * items.  If the item is a group, it may support mkdir(2).
 * Groups supply one of make_group() and make_item().  If the
 * group supports make_group(), one can create group children.  If it
 * supports make_item(), one can create config_item children.  make_group()
 * and make_item() return ERR_PTR() on errors.  If it has
 * default_groups on group->default_groups, it has automatically created
 * group children.  default_groups may coexist alongsize make_group() or
 * make_item(), but if the group wishes to have only default_groups
 * children (disallowing mkdir(2)), it need not provide either function.
 */
struct configfs_item_operations {
        void (*release)(struct config_item *);
        int (*allow_link)(struct config_item *src, struct config_item *target);
        void (*drop_link)(struct config_item *src, struct config_item *target);
};

struct configfs_group_operations {
        struct config_item *(*make_item)(struct config_group *group, const char *name);
        struct config_group *(*make_group)(struct config_group *group, const char *name);
        void (*disconnect_notify)(struct config_group *group, struct config_item *item);
        void (*drop_item)(struct config_group *group, struct config_item *item);
        bool (*is_visible)(struct config_item *item, struct configfs_attribute *attr, int n);
        bool (*is_bin_visible)(struct config_item *item, struct configfs_bin_attribute *attr,
                               int n);
};

struct configfs_subsystem {
        struct config_group     su_group;
        struct mutex            su_mutex;
};

static inline struct configfs_subsystem *to_configfs_subsystem(struct config_group *group)
{
        return group ?
                container_of(group, struct configfs_subsystem, su_group) :
                NULL;
}

int configfs_register_subsystem(struct configfs_subsystem *subsys);
void configfs_unregister_subsystem(struct configfs_subsystem *subsys);

int configfs_register_group(struct config_group *parent_group,
                            struct config_group *group);
void configfs_unregister_group(struct config_group *group);

void configfs_remove_default_groups(struct config_group *group);

struct config_group *
configfs_register_default_group(struct config_group *parent_group,
                                const char *name,
                                const struct config_item_type *item_type);
void configfs_unregister_default_group(struct config_group *group);

/* These functions can sleep and can alloc with GFP_KERNEL */
/* WARNING: These cannot be called underneath configfs callbacks!! */
int configfs_depend_item(struct configfs_subsystem *subsys,
                         struct config_item *target);
void configfs_undepend_item(struct config_item *target);

/*
 * These functions can sleep and can alloc with GFP_KERNEL
 * NOTE: These should be called only underneath configfs callbacks.
 * NOTE: First parameter is a caller's subsystem, not target's.
 * WARNING: These cannot be called on newly created item
 *        (in make_group()/make_item() callback)
 */
int configfs_depend_item_unlocked(struct configfs_subsystem *caller_subsys,
                                  struct config_item *target);


static inline void configfs_undepend_item_unlocked(struct config_item *target)
{
        configfs_undepend_item(target);
}

#endif /* _CONFIGFS_H_ */