staging:iio:Documentation Simple dummy driver to explain the basics

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / drivers / firmware / efivars.c

/*
 * EFI Variables - efivars.c
 *
 * Copyright (C) 2001,2003,2004 Dell <Matt_Domsch@dell.com>
 * Copyright (C) 2004 Intel Corporation <matthew.e.tolentino@intel.com>
 *
 * This code takes all variables accessible from EFI runtime and
 *  exports them via sysfs
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Changelog:
 *
 *  17 May 2004 - Matt Domsch <Matt_Domsch@dell.com>
 *   remove check for efi_enabled in exit
 *   add MODULE_VERSION
 *
 *  26 Apr 2004 - Matt Domsch <Matt_Domsch@dell.com>
 *   minor bug fixes
 *
 *  21 Apr 2004 - Matt Tolentino <matthew.e.tolentino@intel.com)
 *   converted driver to export variable information via sysfs
 *   and moved to drivers/firmware directory
 *   bumped revision number to v0.07 to reflect conversion & move
 *
 *  10 Dec 2002 - Matt Domsch <Matt_Domsch@dell.com>
 *   fix locking per Peter Chubb's findings
 *
 *  25 Mar 2002 - Matt Domsch <Matt_Domsch@dell.com>
 *   move uuid_unparse() to include/asm-ia64/efi.h:efi_guid_unparse()
 *
 *  12 Feb 2002 - Matt Domsch <Matt_Domsch@dell.com>
 *   use list_for_each_safe when deleting vars.
 *   remove ifdef CONFIG_SMP around include <linux/smp.h>
 *   v0.04 release to linux-ia64@linuxia64.org
 *
 *  20 April 2001 - Matt Domsch <Matt_Domsch@dell.com>
 *   Moved vars from /proc/efi to /proc/efi/vars, and made
 *   efi.c own the /proc/efi directory.
 *   v0.03 release to linux-ia64@linuxia64.org
 *
 *  26 March 2001 - Matt Domsch <Matt_Domsch@dell.com>
 *   At the request of Stephane, moved ownership of /proc/efi
 *   to efi.c, and now efivars lives under /proc/efi/vars.
 *
 *  12 March 2001 - Matt Domsch <Matt_Domsch@dell.com>
 *   Feedback received from Stephane Eranian incorporated.
 *   efivar_write() checks copy_from_user() return value.
 *   efivar_read/write() returns proper errno.
 *   v0.02 release to linux-ia64@linuxia64.org
 *
 *  26 February 2001 - Matt Domsch <Matt_Domsch@dell.com>
 *   v0.01 release to linux-ia64@linuxia64.org
 */

#include <linux/capability.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/smp.h>
#include <linux/efi.h>
#include <linux/sysfs.h>
#include <linux/kobject.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/pstore.h>

#include <asm/uaccess.h>

#define EFIVARS_VERSION "0.08"
#define EFIVARS_DATE "2004-May-17"

MODULE_AUTHOR("Matt Domsch <Matt_Domsch@Dell.com>");
MODULE_DESCRIPTION("sysfs interface to EFI Variables");
MODULE_LICENSE("GPL");
MODULE_VERSION(EFIVARS_VERSION);

#define DUMP_NAME_LEN 52

/*
 * The maximum size of VariableName + Data = 1024
 * Therefore, it's reasonable to save that much
 * space in each part of the structure,
 * and we use a page for reading/writing.
 */

struct efi_variable {
        efi_char16_t  VariableName[1024/sizeof(efi_char16_t)];
        efi_guid_t    VendorGuid;
        unsigned long DataSize;
        __u8          Data[1024];
        efi_status_t  Status;
        __u32         Attributes;
} __attribute__((packed));


struct efivar_entry {
        struct efivars *efivars;
        struct efi_variable var;
        struct list_head list;
        struct kobject kobj;
};

struct efivar_attribute {
        struct attribute attr;
        ssize_t (*show) (struct efivar_entry *entry, char *buf);
        ssize_t (*store)(struct efivar_entry *entry, const char *buf, size_t count);
};

#define PSTORE_EFI_ATTRIBUTES \
        (EFI_VARIABLE_NON_VOLATILE | \
         EFI_VARIABLE_BOOTSERVICE_ACCESS | \
         EFI_VARIABLE_RUNTIME_ACCESS)

#define EFIVAR_ATTR(_name, _mode, _show, _store) \
struct efivar_attribute efivar_attr_##_name = { \
        .attr = {.name = __stringify(_name), .mode = _mode}, \
        .show = _show, \
        .store = _store, \
};

#define to_efivar_attr(_attr) container_of(_attr, struct efivar_attribute, attr)
#define to_efivar_entry(obj)  container_of(obj, struct efivar_entry, kobj)

/*
 * Prototype for sysfs creation function
 */
static int
efivar_create_sysfs_entry(struct efivars *efivars,
                          unsigned long variable_name_size,
                          efi_char16_t *variable_name,
                          efi_guid_t *vendor_guid);

/* Return the number of unicode characters in data */
static unsigned long
utf16_strnlen(efi_char16_t *s, size_t maxlength)
{
        unsigned long length = 0;

        while (*s++ != 0 && length < maxlength)
                length++;
        return length;
}

static inline unsigned long
utf16_strlen(efi_char16_t *s)
{
        return utf16_strnlen(s, ~0UL);
}

/*
 * Return the number of bytes is the length of this string
 * Note: this is NOT the same as the number of unicode characters
 */
static inline unsigned long
utf16_strsize(efi_char16_t *data, unsigned long maxlength)
{
        return utf16_strnlen(data, maxlength/sizeof(efi_char16_t)) * sizeof(efi_char16_t);
}

static inline int
utf16_strncmp(const efi_char16_t *a, const efi_char16_t *b, size_t len)
{
        while (1) {
                if (len == 0)
                        return 0;
                if (*a < *b)
                        return -1;
                if (*a > *b)
                        return 1;
                if (*a == 0) /* implies *b == 0 */
                        return 0;
                a++;
                b++;
                len--;
        }
}

static efi_status_t
get_var_data_locked(struct efivars *efivars, struct efi_variable *var)
{
        efi_status_t status;

        var->DataSize = 1024;
        status = efivars->ops->get_variable(var->VariableName,
                                            &var->VendorGuid,
                                            &var->Attributes,
                                            &var->DataSize,
                                            var->Data);
        return status;
}

static efi_status_t
get_var_data(struct efivars *efivars, struct efi_variable *var)
{
        efi_status_t status;

        spin_lock(&efivars->lock);
        status = get_var_data_locked(efivars, var);
        spin_unlock(&efivars->lock);

        if (status != EFI_SUCCESS) {
                printk(KERN_WARNING "efivars: get_variable() failed 0x%lx!\n",
                        status);
        }
        return status;
}

static ssize_t
efivar_guid_read(struct efivar_entry *entry, char *buf)
{
        struct efi_variable *var = &entry->var;
        char *str = buf;

        if (!entry || !buf)
                return 0;

        efi_guid_unparse(&var->VendorGuid, str);
        str += strlen(str);
        str += sprintf(str, "\n");

        return str - buf;
}

static ssize_t
efivar_attr_read(struct efivar_entry *entry, char *buf)
{
        struct efi_variable *var = &entry->var;
        char *str = buf;
        efi_status_t status;

        if (!entry || !buf)
                return -EINVAL;

        status = get_var_data(entry->efivars, var);
        if (status != EFI_SUCCESS)
                return -EIO;

        if (var->Attributes & 0x1)
                str += sprintf(str, "EFI_VARIABLE_NON_VOLATILE\n");
        if (var->Attributes & 0x2)
                str += sprintf(str, "EFI_VARIABLE_BOOTSERVICE_ACCESS\n");
        if (var->Attributes & 0x4)
                str += sprintf(str, "EFI_VARIABLE_RUNTIME_ACCESS\n");
        return str - buf;
}

static ssize_t
efivar_size_read(struct efivar_entry *entry, char *buf)
{
        struct efi_variable *var = &entry->var;
        char *str = buf;
        efi_status_t status;

        if (!entry || !buf)
                return -EINVAL;

        status = get_var_data(entry->efivars, var);
        if (status != EFI_SUCCESS)
                return -EIO;

        str += sprintf(str, "0x%lx\n", var->DataSize);
        return str - buf;
}

static ssize_t
efivar_data_read(struct efivar_entry *entry, char *buf)
{
        struct efi_variable *var = &entry->var;
        efi_status_t status;

        if (!entry || !buf)
                return -EINVAL;

        status = get_var_data(entry->efivars, var);
        if (status != EFI_SUCCESS)
                return -EIO;

        memcpy(buf, var->Data, var->DataSize);
        return var->DataSize;
}
/*
 * We allow each variable to be edited via rewriting the
 * entire efi variable structure.
 */
static ssize_t
efivar_store_raw(struct efivar_entry *entry, const char *buf, size_t count)
{
        struct efi_variable *new_var, *var = &entry->var;
        struct efivars *efivars = entry->efivars;
        efi_status_t status = EFI_NOT_FOUND;

        if (count != sizeof(struct efi_variable))
                return -EINVAL;

        new_var = (struct efi_variable *)buf;
        /*
         * If only updating the variable data, then the name
         * and guid should remain the same
         */
        if (memcmp(new_var->VariableName, var->VariableName, sizeof(var->VariableName)) ||
                efi_guidcmp(new_var->VendorGuid, var->VendorGuid)) {
                printk(KERN_ERR "efivars: Cannot edit the wrong variable!\n");
                return -EINVAL;
        }

        if ((new_var->DataSize <= 0) || (new_var->Attributes == 0)){
                printk(KERN_ERR "efivars: DataSize & Attributes must be valid!\n");
                return -EINVAL;
        }

        spin_lock(&efivars->lock);
        status = efivars->ops->set_variable(new_var->VariableName,
                                            &new_var->VendorGuid,
                                            new_var->Attributes,
                                            new_var->DataSize,
                                            new_var->Data);

        spin_unlock(&efivars->lock);

        if (status != EFI_SUCCESS) {
                printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
                        status);
                return -EIO;
        }

        memcpy(&entry->var, new_var, count);
        return count;
}

static ssize_t
efivar_show_raw(struct efivar_entry *entry, char *buf)
{
        struct efi_variable *var = &entry->var;
        efi_status_t status;

        if (!entry || !buf)
                return 0;

        status = get_var_data(entry->efivars, var);
        if (status != EFI_SUCCESS)
                return -EIO;

        memcpy(buf, var, sizeof(*var));
        return sizeof(*var);
}

/*
 * Generic read/write functions that call the specific functions of
 * the attributes...
 */
static ssize_t efivar_attr_show(struct kobject *kobj, struct attribute *attr,
                                char *buf)
{
        struct efivar_entry *var = to_efivar_entry(kobj);
        struct efivar_attribute *efivar_attr = to_efivar_attr(attr);
        ssize_t ret = -EIO;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        if (efivar_attr->show) {
                ret = efivar_attr->show(var, buf);
        }
        return ret;
}

static ssize_t efivar_attr_store(struct kobject *kobj, struct attribute *attr,
                                const char *buf, size_t count)
{
        struct efivar_entry *var = to_efivar_entry(kobj);
        struct efivar_attribute *efivar_attr = to_efivar_attr(attr);
        ssize_t ret = -EIO;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        if (efivar_attr->store)
                ret = efivar_attr->store(var, buf, count);

        return ret;
}

static const struct sysfs_ops efivar_attr_ops = {
        .show = efivar_attr_show,
        .store = efivar_attr_store,
};

static void efivar_release(struct kobject *kobj)
{
        struct efivar_entry *var = container_of(kobj, struct efivar_entry, kobj);
        kfree(var);
}

static EFIVAR_ATTR(guid, 0400, efivar_guid_read, NULL);
static EFIVAR_ATTR(attributes, 0400, efivar_attr_read, NULL);
static EFIVAR_ATTR(size, 0400, efivar_size_read, NULL);
static EFIVAR_ATTR(data, 0400, efivar_data_read, NULL);
static EFIVAR_ATTR(raw_var, 0600, efivar_show_raw, efivar_store_raw);

static struct attribute *def_attrs[] = {
        &efivar_attr_guid.attr,
        &efivar_attr_size.attr,
        &efivar_attr_attributes.attr,
        &efivar_attr_data.attr,
        &efivar_attr_raw_var.attr,
        NULL,
};

static struct kobj_type efivar_ktype = {
        .release = efivar_release,
        .sysfs_ops = &efivar_attr_ops,
        .default_attrs = def_attrs,
};

static struct pstore_info efi_pstore_info;

static inline void
efivar_unregister(struct efivar_entry *var)
{
        kobject_put(&var->kobj);
}

#ifdef CONFIG_PSTORE

static int efi_pstore_open(struct pstore_info *psi)
{
        struct efivars *efivars = psi->data;

        spin_lock(&efivars->lock);
        efivars->walk_entry = list_first_entry(&efivars->list,
                                               struct efivar_entry, list);
        return 0;
}

static int efi_pstore_close(struct pstore_info *psi)
{
        struct efivars *efivars = psi->data;

        spin_unlock(&efivars->lock);
        return 0;
}

static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
                               struct timespec *timespec, struct pstore_info *psi)
{
        efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
        struct efivars *efivars = psi->data;
        char name[DUMP_NAME_LEN];
        int i;
        unsigned int part, size;
        unsigned long time;

        while (&efivars->walk_entry->list != &efivars->list) {
                if (!efi_guidcmp(efivars->walk_entry->var.VendorGuid,
                                 vendor)) {
                        for (i = 0; i < DUMP_NAME_LEN; i++) {
                                name[i] = efivars->walk_entry->var.VariableName[i];
                        }
                        if (sscanf(name, "dump-type%u-%u-%lu", type, &part, &time) == 3) {
                                *id = part;
                                timespec->tv_sec = time;
                                timespec->tv_nsec = 0;
                                get_var_data_locked(efivars, &efivars->walk_entry->var);
                                size = efivars->walk_entry->var.DataSize;
                                memcpy(psi->buf, efivars->walk_entry->var.Data, size);
                                efivars->walk_entry = list_entry(efivars->walk_entry->list.next,
                                                   struct efivar_entry, list);
                                return size;
                        }
                }
                efivars->walk_entry = list_entry(efivars->walk_entry->list.next,
                                                 struct efivar_entry, list);
        }
        return 0;
}

static u64 efi_pstore_write(enum pstore_type_id type, unsigned int part,
                            size_t size, struct pstore_info *psi)
{
        char name[DUMP_NAME_LEN];
        char stub_name[DUMP_NAME_LEN];
        efi_char16_t efi_name[DUMP_NAME_LEN];
        efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
        struct efivars *efivars = psi->data;
        struct efivar_entry *entry, *found = NULL;
        int i;

        sprintf(stub_name, "dump-type%u-%u-", type, part);
        sprintf(name, "%s%lu", stub_name, get_seconds());

        spin_lock(&efivars->lock);

        for (i = 0; i < DUMP_NAME_LEN; i++)
                efi_name[i] = stub_name[i];

        /*
         * Clean up any entries with the same name
         */

        list_for_each_entry(entry, &efivars->list, list) {
                get_var_data_locked(efivars, &entry->var);

                if (efi_guidcmp(entry->var.VendorGuid, vendor))
                        continue;
                if (utf16_strncmp(entry->var.VariableName, efi_name,
                                  utf16_strlen(efi_name)))
                        continue;
                /* Needs to be a prefix */
                if (entry->var.VariableName[utf16_strlen(efi_name)] == 0)
                        continue;

                /* found */
                found = entry;
                efivars->ops->set_variable(entry->var.VariableName,
                                           &entry->var.VendorGuid,
                                           PSTORE_EFI_ATTRIBUTES,
                                           0, NULL);
        }

        if (found)
                list_del(&found->list);

        for (i = 0; i < DUMP_NAME_LEN; i++)
                efi_name[i] = name[i];

        efivars->ops->set_variable(efi_name, &vendor, PSTORE_EFI_ATTRIBUTES,
                                   size, psi->buf);

        spin_unlock(&efivars->lock);

        if (found)
                efivar_unregister(found);

        if (size)
                efivar_create_sysfs_entry(efivars,
                                          utf16_strsize(efi_name,
                                                        DUMP_NAME_LEN * 2),
                                          efi_name, &vendor);

        return part;
};

static int efi_pstore_erase(enum pstore_type_id type, u64 id,
                            struct pstore_info *psi)
{
        efi_pstore_write(type, id, 0, psi);

        return 0;
}
#else
static int efi_pstore_open(struct pstore_info *psi)
{
        return 0;
}

static int efi_pstore_close(struct pstore_info *psi)
{
        return 0;
}

static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
                               struct timespec *time, struct pstore_info *psi)
{
        return -1;
}

static u64 efi_pstore_write(enum pstore_type_id type, unsigned int part,
                            size_t size, struct pstore_info *psi)
{
        return 0;
}

static int efi_pstore_erase(enum pstore_type_id type, u64 id,
                            struct pstore_info *psi)
{
        return 0;
}
#endif

static struct pstore_info efi_pstore_info = {
        .owner          = THIS_MODULE,
        .name           = "efi",
        .open           = efi_pstore_open,
        .close          = efi_pstore_close,
        .read           = efi_pstore_read,
        .write          = efi_pstore_write,
        .erase          = efi_pstore_erase,
};

static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
                             struct bin_attribute *bin_attr,
                             char *buf, loff_t pos, size_t count)
{
        struct efi_variable *new_var = (struct efi_variable *)buf;
        struct efivars *efivars = bin_attr->private;
        struct efivar_entry *search_efivar, *n;
        unsigned long strsize1, strsize2;
        efi_status_t status = EFI_NOT_FOUND;
        int found = 0;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        spin_lock(&efivars->lock);

        /*
         * Does this variable already exist?
         */
        list_for_each_entry_safe(search_efivar, n, &efivars->list, list) {
                strsize1 = utf16_strsize(search_efivar->var.VariableName, 1024);
                strsize2 = utf16_strsize(new_var->VariableName, 1024);
                if (strsize1 == strsize2 &&
                        !memcmp(&(search_efivar->var.VariableName),
                                new_var->VariableName, strsize1) &&
                        !efi_guidcmp(search_efivar->var.VendorGuid,
                                new_var->VendorGuid)) {
                        found = 1;
                        break;
                }
        }
        if (found) {
                spin_unlock(&efivars->lock);
                return -EINVAL;
        }

        /* now *really* create the variable via EFI */
        status = efivars->ops->set_variable(new_var->VariableName,
                                            &new_var->VendorGuid,
                                            new_var->Attributes,
                                            new_var->DataSize,
                                            new_var->Data);

        if (status != EFI_SUCCESS) {
                printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
                        status);
                spin_unlock(&efivars->lock);
                return -EIO;
        }
        spin_unlock(&efivars->lock);

        /* Create the entry in sysfs.  Locking is not required here */
        status = efivar_create_sysfs_entry(efivars,
                                           utf16_strsize(new_var->VariableName,
                                                         1024),
                                           new_var->VariableName,
                                           &new_var->VendorGuid);
        if (status) {
                printk(KERN_WARNING "efivars: variable created, but sysfs entry wasn't.\n");
        }
        return count;
}

static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
                             struct bin_attribute *bin_attr,
                             char *buf, loff_t pos, size_t count)
{
        struct efi_variable *del_var = (struct efi_variable *)buf;
        struct efivars *efivars = bin_attr->private;
        struct efivar_entry *search_efivar, *n;
        unsigned long strsize1, strsize2;
        efi_status_t status = EFI_NOT_FOUND;
        int found = 0;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        spin_lock(&efivars->lock);

        /*
         * Does this variable already exist?
         */
        list_for_each_entry_safe(search_efivar, n, &efivars->list, list) {
                strsize1 = utf16_strsize(search_efivar->var.VariableName, 1024);
                strsize2 = utf16_strsize(del_var->VariableName, 1024);
                if (strsize1 == strsize2 &&
                        !memcmp(&(search_efivar->var.VariableName),
                                del_var->VariableName, strsize1) &&
                        !efi_guidcmp(search_efivar->var.VendorGuid,
                                del_var->VendorGuid)) {
                        found = 1;
                        break;
                }
        }
        if (!found) {
                spin_unlock(&efivars->lock);
                return -EINVAL;
        }
        /* force the Attributes/DataSize to 0 to ensure deletion */
        del_var->Attributes = 0;
        del_var->DataSize = 0;

        status = efivars->ops->set_variable(del_var->VariableName,
                                            &del_var->VendorGuid,
                                            del_var->Attributes,
                                            del_var->DataSize,
                                            del_var->Data);

        if (status != EFI_SUCCESS) {
                printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
                        status);
                spin_unlock(&efivars->lock);
                return -EIO;
        }
        list_del(&search_efivar->list);
        /* We need to release this lock before unregistering. */
        spin_unlock(&efivars->lock);
        efivar_unregister(search_efivar);

        /* It's dead Jim.... */
        return count;
}

/*
 * Let's not leave out systab information that snuck into
 * the efivars driver
 */
static ssize_t systab_show(struct kobject *kobj,
                           struct kobj_attribute *attr, char *buf)
{
        char *str = buf;

        if (!kobj || !buf)
                return -EINVAL;

        if (efi.mps != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "MPS=0x%lx\n", efi.mps);
        if (efi.acpi20 != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "ACPI20=0x%lx\n", efi.acpi20);
        if (efi.acpi != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "ACPI=0x%lx\n", efi.acpi);
        if (efi.smbios != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "SMBIOS=0x%lx\n", efi.smbios);
        if (efi.hcdp != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "HCDP=0x%lx\n", efi.hcdp);
        if (efi.boot_info != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "BOOTINFO=0x%lx\n", efi.boot_info);
        if (efi.uga != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "UGA=0x%lx\n", efi.uga);

        return str - buf;
}

static struct kobj_attribute efi_attr_systab =
                        __ATTR(systab, 0400, systab_show, NULL);

static struct attribute *efi_subsys_attrs[] = {
        &efi_attr_systab.attr,
        NULL,   /* maybe more in the future? */
};

static struct attribute_group efi_subsys_attr_group = {
        .attrs = efi_subsys_attrs,
};

static struct kobject *efi_kobj;

/*
 * efivar_create_sysfs_entry()
 * Requires:
 *    variable_name_size = number of bytes required to hold
 *                         variable_name (not counting the NULL
 *                         character at the end.
 *    efivars->lock is not held on entry or exit.
 * Returns 1 on failure, 0 on success
 */
static int
efivar_create_sysfs_entry(struct efivars *efivars,
                          unsigned long variable_name_size,
                          efi_char16_t *variable_name,
                          efi_guid_t *vendor_guid)
{
        int i, short_name_size = variable_name_size / sizeof(efi_char16_t) + 38;
        char *short_name;
        struct efivar_entry *new_efivar;

        short_name = kzalloc(short_name_size + 1, GFP_KERNEL);
        new_efivar = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);

        if (!short_name || !new_efivar)  {
                kfree(short_name);
                kfree(new_efivar);
                return 1;
        }

        new_efivar->efivars = efivars;
        memcpy(new_efivar->var.VariableName, variable_name,
                variable_name_size);
        memcpy(&(new_efivar->var.VendorGuid), vendor_guid, sizeof(efi_guid_t));

        /* Convert Unicode to normal chars (assume top bits are 0),
           ala UTF-8 */
        for (i=0; i < (int)(variable_name_size / sizeof(efi_char16_t)); i++) {
                short_name[i] = variable_name[i] & 0xFF;
        }
        /* This is ugly, but necessary to separate one vendor's
           private variables from another's.         */

        *(short_name + strlen(short_name)) = '-';
        efi_guid_unparse(vendor_guid, short_name + strlen(short_name));

        new_efivar->kobj.kset = efivars->kset;
        i = kobject_init_and_add(&new_efivar->kobj, &efivar_ktype, NULL,
                                 "%s", short_name);
        if (i) {
                kfree(short_name);
                kfree(new_efivar);
                return 1;
        }

        kobject_uevent(&new_efivar->kobj, KOBJ_ADD);
        kfree(short_name);
        short_name = NULL;

        spin_lock(&efivars->lock);
        list_add(&new_efivar->list, &efivars->list);
        spin_unlock(&efivars->lock);

        return 0;
}

static int
create_efivars_bin_attributes(struct efivars *efivars)
{
        struct bin_attribute *attr;
        int error;

        /* new_var */
        attr = kzalloc(sizeof(*attr), GFP_KERNEL);
        if (!attr)
                return -ENOMEM;

        attr->attr.name = "new_var";
        attr->attr.mode = 0200;
        attr->write = efivar_create;
        attr->private = efivars;
        efivars->new_var = attr;

        /* del_var */
        attr = kzalloc(sizeof(*attr), GFP_KERNEL);
        if (!attr) {
                error = -ENOMEM;
                goto out_free;
        }
        attr->attr.name = "del_var";
        attr->attr.mode = 0200;
        attr->write = efivar_delete;
        attr->private = efivars;
        efivars->del_var = attr;

        sysfs_bin_attr_init(efivars->new_var);
        sysfs_bin_attr_init(efivars->del_var);

        /* Register */
        error = sysfs_create_bin_file(&efivars->kset->kobj,
                                      efivars->new_var);
        if (error) {
                printk(KERN_ERR "efivars: unable to create new_var sysfs file"
                        " due to error %d\n", error);
                goto out_free;
        }
        error = sysfs_create_bin_file(&efivars->kset->kobj,
                                      efivars->del_var);
        if (error) {
                printk(KERN_ERR "efivars: unable to create del_var sysfs file"
                        " due to error %d\n", error);
                sysfs_remove_bin_file(&efivars->kset->kobj,
                                      efivars->new_var);
                goto out_free;
        }

        return 0;
out_free:
        kfree(efivars->del_var);
        efivars->del_var = NULL;
        kfree(efivars->new_var);
        efivars->new_var = NULL;
        return error;
}

void unregister_efivars(struct efivars *efivars)
{
        struct efivar_entry *entry, *n;

        list_for_each_entry_safe(entry, n, &efivars->list, list) {
                spin_lock(&efivars->lock);
                list_del(&entry->list);
                spin_unlock(&efivars->lock);
                efivar_unregister(entry);
        }
        if (efivars->new_var)
                sysfs_remove_bin_file(&efivars->kset->kobj, efivars->new_var);
        if (efivars->del_var)
                sysfs_remove_bin_file(&efivars->kset->kobj, efivars->del_var);
        kfree(efivars->new_var);
        kfree(efivars->del_var);
        kset_unregister(efivars->kset);
}
EXPORT_SYMBOL_GPL(unregister_efivars);

int register_efivars(struct efivars *efivars,
                     const struct efivar_operations *ops,
                     struct kobject *parent_kobj)
{
        efi_status_t status = EFI_NOT_FOUND;
        efi_guid_t vendor_guid;
        efi_char16_t *variable_name;
        unsigned long variable_name_size = 1024;
        int error = 0;

        variable_name = kzalloc(variable_name_size, GFP_KERNEL);
        if (!variable_name) {
                printk(KERN_ERR "efivars: Memory allocation failed.\n");
                return -ENOMEM;
        }

        spin_lock_init(&efivars->lock);
        INIT_LIST_HEAD(&efivars->list);
        efivars->ops = ops;

        efivars->kset = kset_create_and_add("vars", NULL, parent_kobj);
        if (!efivars->kset) {
                printk(KERN_ERR "efivars: Subsystem registration failed.\n");
                error = -ENOMEM;
                goto out;
        }

        /*
         * Per EFI spec, the maximum storage allocated for both
         * the variable name and variable data is 1024 bytes.
         */

        do {
                variable_name_size = 1024;

                status = ops->get_next_variable(&variable_name_size,
                                                variable_name,
                                                &vendor_guid);
                switch (status) {
                case EFI_SUCCESS:
                        efivar_create_sysfs_entry(efivars,
                                                  variable_name_size,
                                                  variable_name,
                                                  &vendor_guid);
                        break;
                case EFI_NOT_FOUND:
                        break;
                default:
                        printk(KERN_WARNING "efivars: get_next_variable: status=%lx\n",
                                status);
                        status = EFI_NOT_FOUND;
                        break;
                }
        } while (status != EFI_NOT_FOUND);

        error = create_efivars_bin_attributes(efivars);
        if (error)
                unregister_efivars(efivars);

        efivars->efi_pstore_info = efi_pstore_info;

        efivars->efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
        if (efivars->efi_pstore_info.buf) {
                efivars->efi_pstore_info.bufsize = 1024;
                efivars->efi_pstore_info.data = efivars;
                mutex_init(&efivars->efi_pstore_info.buf_mutex);
                pstore_register(&efivars->efi_pstore_info);
        }

out:
        kfree(variable_name);

        return error;
}
EXPORT_SYMBOL_GPL(register_efivars);

static struct efivars __efivars;
static struct efivar_operations ops;

/*
 * For now we register the efi subsystem with the firmware subsystem
 * and the vars subsystem with the efi subsystem.  In the future, it
 * might make sense to split off the efi subsystem into its own
 * driver, but for now only efivars will register with it, so just
 * include it here.
 */

static int __init
efivars_init(void)
{
        int error = 0;

        printk(KERN_INFO "EFI Variables Facility v%s %s\n", EFIVARS_VERSION,
               EFIVARS_DATE);

        if (!efi_enabled)
                return 0;

        /* For now we'll register the efi directory at /sys/firmware/efi */
        efi_kobj = kobject_create_and_add("efi", firmware_kobj);
        if (!efi_kobj) {
                printk(KERN_ERR "efivars: Firmware registration failed.\n");
                return -ENOMEM;
        }

        ops.get_variable = efi.get_variable;
        ops.set_variable = efi.set_variable;
        ops.get_next_variable = efi.get_next_variable;
        error = register_efivars(&__efivars, &ops, efi_kobj);
        if (error)
                goto err_put;

        /* Don't forget the systab entry */
        error = sysfs_create_group(efi_kobj, &efi_subsys_attr_group);
        if (error) {
                printk(KERN_ERR
                       "efivars: Sysfs attribute export failed with error %d.\n",
                       error);
                goto err_unregister;
        }

        return 0;

err_unregister:
        unregister_efivars(&__efivars);
err_put:
        kobject_put(efi_kobj);
        return error;
}

static void __exit
efivars_exit(void)
{
        if (efi_enabled) {
                unregister_efivars(&__efivars);
                kobject_put(efi_kobj);
        }
}

module_init(efivars_init);
module_exit(efivars_exit);