drivers/firmware/efi/efi.c

   1 /*
   2  * efi.c - EFI subsystem
   3  *
   4  * Copyright (C) 2001,2003,2004 Dell <Matt_Domsch@dell.com>
   5  * Copyright (C) 2004 Intel Corporation <matthew.e.tolentino@intel.com>
   6  * Copyright (C) 2013 Tom Gundersen <teg@jklm.no>
   7  *
   8  * This code registers /sys/firmware/efi{,/efivars} when EFI is supported,
   9  * allowing the efivarfs to be mounted or the efivars module to be loaded.
  10  * The existance of /sys/firmware/efi may also be used by userspace to
  11  * determine that the system supports EFI.
  12  *
  13  * This file is released under the GPLv2.
  14  */
  15
  16 #include <linux/kobject.h>
  17 #include <linux/module.h>
  18 #include <linux/init.h>
  19 #include <linux/device.h>
  20 #include <linux/efi.h>
  21
  22 static struct kobject *efi_kobj;
  23 static struct kobject *efivars_kobj;
  24
  25 /*
  26  * Let's not leave out systab information that snuck into
  27  * the efivars driver
  28  */
  29 static ssize_t systab_show(struct kobject *kobj,
  30                            struct kobj_attribute *attr, char *buf)
  31 {
  32         char *str = buf;
  33
  34         if (!kobj || !buf)
  35                 return -EINVAL;
  36
  37         if (efi.mps != EFI_INVALID_TABLE_ADDR)
  38                 str += sprintf(str, "MPS=0x%lx\n", efi.mps);
  39         if (efi.acpi20 != EFI_INVALID_TABLE_ADDR)
  40                 str += sprintf(str, "ACPI20=0x%lx\n", efi.acpi20);
  41         if (efi.acpi != EFI_INVALID_TABLE_ADDR)
  42                 str += sprintf(str, "ACPI=0x%lx\n", efi.acpi);
  43         if (efi.smbios != EFI_INVALID_TABLE_ADDR)
  44                 str += sprintf(str, "SMBIOS=0x%lx\n", efi.smbios);
  45         if (efi.hcdp != EFI_INVALID_TABLE_ADDR)
  46                 str += sprintf(str, "HCDP=0x%lx\n", efi.hcdp);
  47         if (efi.boot_info != EFI_INVALID_TABLE_ADDR)
  48                 str += sprintf(str, "BOOTINFO=0x%lx\n", efi.boot_info);
  49         if (efi.uga != EFI_INVALID_TABLE_ADDR)
  50                 str += sprintf(str, "UGA=0x%lx\n", efi.uga);
  51
  52         return str - buf;
  53 }
  54
  55 static struct kobj_attribute efi_attr_systab =
  56                         __ATTR(systab, 0400, systab_show, NULL);
  57
  58 static struct attribute *efi_subsys_attrs[] = {
  59         &efi_attr_systab.attr,
  60         NULL,   /* maybe more in the future? */
  61 };
  62
  63 static struct attribute_group efi_subsys_attr_group = {
  64         .attrs = efi_subsys_attrs,
  65 };
  66
  67 static struct efivars generic_efivars;
  68 static struct efivar_operations generic_ops;
  69
  70 static int generic_ops_register(void)
  71 {
  72         generic_ops.get_variable = efi.get_variable;
  73         generic_ops.set_variable = efi.set_variable;
  74         generic_ops.get_next_variable = efi.get_next_variable;
  75         generic_ops.query_variable_info = efi.query_variable_info;
  76
  77         return efivars_register(&generic_efivars, &generic_ops, efi_kobj);
  78 }
  79
  80 static void generic_ops_unregister(void)
  81 {
  82         efivars_unregister(&generic_efivars);
  83 }
  84
  85 /*
  86  * We register the efi subsystem with the firmware subsystem and the
  87  * efivars subsystem with the efi subsystem, if the system was booted with
  88  * EFI.
  89  */
  90 static int __init efisubsys_init(void)
  91 {
  92         int error;
  93
  94         if (!efi_enabled(EFI_BOOT))
  95                 return 0;
  96
  97         /* We register the efi directory at /sys/firmware/efi */
  98         efi_kobj = kobject_create_and_add("efi", firmware_kobj);
  99         if (!efi_kobj) {
 100                 pr_err("efi: Firmware registration failed.\n");
 101                 return -ENOMEM;
 102         }
 103
 104         error = generic_ops_register();
 105         if (error)
 106                 goto err_put;
 107
 108         error = sysfs_create_group(efi_kobj, &efi_subsys_attr_group);
 109         if (error) {
 110                 pr_err("efi: Sysfs attribute export failed with error %d.\n",
 111                        error);
 112                 goto err_unregister;
 113         }
 114
 115         /* and the standard mountpoint for efivarfs */
 116         efivars_kobj = kobject_create_and_add("efivars", efi_kobj);
 117         if (!efivars_kobj) {
 118                 pr_err("efivars: Subsystem registration failed.\n");
 119                 error = -ENOMEM;
 120                 goto err_remove_group;
 121         }
 122
 123         return 0;
 124
 125 err_remove_group:
 126         sysfs_remove_group(efi_kobj, &efi_subsys_attr_group);
 127 err_unregister:
 128         generic_ops_unregister();
 129 err_put:
 130         kobject_put(efi_kobj);
 131         return error;
 132 }
 133
 134 subsys_initcall(efisubsys_init);