LXR linux/drivers/firmware/efi/dev-path-parser.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * dev-path-parser.c - EFI Device Path parser
   4 * Copyright (C) 2016 Lukas Wunner <lukas@wunner.de>
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License (version 2) as
   8 * published by the Free Software Foundation.
   9 */
  10
  11#include <linux/acpi.h>
  12#include <linux/efi.h>
  13#include <linux/pci.h>
  14
  15struct acpi_hid_uid {
  16        struct acpi_device_id hid[2];
  17        char uid[11]; /* UINT_MAX + null byte */
  18};
  19
  20static int __init match_acpi_dev(struct device *dev, const void *data)
  21{
  22        struct acpi_hid_uid hid_uid = *(const struct acpi_hid_uid *)data;
  23        struct acpi_device *adev = to_acpi_device(dev);
  24
  25        if (acpi_match_device_ids(adev, hid_uid.hid))
  26                return 0;
  27
  28        if (adev->pnp.unique_id)
  29                return !strcmp(adev->pnp.unique_id, hid_uid.uid);
  30        else
  31                return !strcmp("0", hid_uid.uid);
  32}
  33
  34static long __init parse_acpi_path(struct efi_dev_path *node,
  35                                   struct device *parent, struct device **child)
  36{
  37        struct acpi_hid_uid hid_uid = {};
  38        struct device *phys_dev;
  39
  40        if (node->length != 12)
  41                return -EINVAL;
  42
  43        sprintf(hid_uid.hid[0].id, "%c%c%c%04X",
  44                'A' + ((node->acpi.hid >> 10) & 0x1f) - 1,
  45                'A' + ((node->acpi.hid >>  5) & 0x1f) - 1,
  46                'A' + ((node->acpi.hid >>  0) & 0x1f) - 1,
  47                        node->acpi.hid >> 16);
  48        sprintf(hid_uid.uid, "%u", node->acpi.uid);
  49
  50        *child = bus_find_device(&acpi_bus_type, NULL, &hid_uid,
  51                                 match_acpi_dev);
  52        if (!*child)
  53                return -ENODEV;
  54
  55        phys_dev = acpi_get_first_physical_node(to_acpi_device(*child));
  56        if (phys_dev) {
  57                get_device(phys_dev);
  58                put_device(*child);
  59                *child = phys_dev;
  60        }
  61
  62        return 0;
  63}
  64
  65static int __init match_pci_dev(struct device *dev, void *data)
  66{
  67        unsigned int devfn = *(unsigned int *)data;
  68
  69        return dev_is_pci(dev) && to_pci_dev(dev)->devfn == devfn;
  70}
  71
  72static long __init parse_pci_path(struct efi_dev_path *node,
  73                                  struct device *parent, struct device **child)
  74{
  75        unsigned int devfn;
  76
  77        if (node->length != 6)
  78                return -EINVAL;
  79        if (!parent)
  80                return -EINVAL;
  81
  82        devfn = PCI_DEVFN(node->pci.dev, node->pci.fn);
  83
  84        *child = device_find_child(parent, &devfn, match_pci_dev);
  85        if (!*child)
  86                return -ENODEV;
  87
  88        return 0;
  89}
  90
  91/*
  92 * Insert parsers for further node types here.
  93 *
  94 * Each parser takes a pointer to the @node and to the @parent (will be NULL
  95 * for the first device path node). If a device corresponding to @node was
  96 * found below @parent, its reference count should be incremented and the
  97 * device returned in @child.
  98 *
  99 * The return value should be 0 on success or a negative int on failure.
 100 * The special return values 0x01 (EFI_DEV_END_INSTANCE) and 0xFF
 101 * (EFI_DEV_END_ENTIRE) signal the end of the device path, only
 102 * parse_end_path() is supposed to return this.
 103 *
 104 * Be sure to validate the node length and contents before commencing the
 105 * search for a device.
 106 */
 107
 108static long __init parse_end_path(struct efi_dev_path *node,
 109                                  struct device *parent, struct device **child)
 110{
 111        if (node->length != 4)
 112                return -EINVAL;
 113        if (node->sub_type != EFI_DEV_END_INSTANCE &&
 114            node->sub_type != EFI_DEV_END_ENTIRE)
 115                return -EINVAL;
 116        if (!parent)
 117                return -ENODEV;
 118
 119        *child = get_device(parent);
 120        return node->sub_type;
 121}
 122
 123/**
 124 * efi_get_device_by_path - find device by EFI Device Path
 125 * @node: EFI Device Path
 126 * @len: maximum length of EFI Device Path in bytes
 127 *
 128 * Parse a series of EFI Device Path nodes at @node and find the corresponding
 129 * device.  If the device was found, its reference count is incremented and a
 130 * pointer to it is returned.  The caller needs to drop the reference with
 131 * put_device() after use.  The @node pointer is updated to point to the
 132 * location immediately after the "End of Hardware Device Path" node.
 133 *
 134 * If another Device Path instance follows, @len is decremented by the number
 135 * of bytes consumed.  Otherwise @len is set to %0.
 136 *
 137 * If a Device Path node is malformed or its corresponding device is not found,
 138 * @node is updated to point to this offending node and an ERR_PTR is returned.
 139 *
 140 * If @len is initially %0, the function returns %NULL.  Thus, to iterate over
 141 * all instances in a path, the following idiom may be used:
 142 *
 143 *      while (!IS_ERR_OR_NULL(dev = efi_get_device_by_path(&node, &len))) {
 144 *              // do something with dev
 145 *              put_device(dev);
 146 *      }
 147 *      if (IS_ERR(dev))
 148 *              // report error
 149 *
 150 * Devices can only be found if they're already instantiated. Most buses
 151 * instantiate devices in the "subsys" initcall level, hence the earliest
 152 * initcall level in which this function should be called is "fs".
 153 *
 154 * Returns the device on success or
 155 *      %ERR_PTR(-ENODEV) if no device was found,
 156 *      %ERR_PTR(-EINVAL) if a node is malformed or exceeds @len,
 157 *      %ERR_PTR(-ENOTSUPP) if support for a node type is not yet implemented.
 158 */
 159struct device * __init efi_get_device_by_path(struct efi_dev_path **node,
 160                                              size_t *len)
 161{
 162        struct device *parent = NULL, *child;
 163        long ret = 0;
 164
 165        if (!*len)
 166                return NULL;
 167
 168        while (!ret) {
 169                if (*len < 4 || *len < (*node)->length)
 170                        ret = -EINVAL;
 171                else if ((*node)->type     == EFI_DEV_ACPI &&
 172                         (*node)->sub_type == EFI_DEV_BASIC_ACPI)
 173                        ret = parse_acpi_path(*node, parent, &child);
 174                else if ((*node)->type     == EFI_DEV_HW &&
 175                         (*node)->sub_type == EFI_DEV_PCI)
 176                        ret = parse_pci_path(*node, parent, &child);
 177                else if (((*node)->type    == EFI_DEV_END_PATH ||
 178                          (*node)->type    == EFI_DEV_END_PATH2))
 179                        ret = parse_end_path(*node, parent, &child);
 180                else
 181                        ret = -ENOTSUPP;
 182
 183                put_device(parent);
 184                if (ret < 0)
 185                        return ERR_PTR(ret);
 186
 187                parent = child;
 188                *node  = (void *)*node + (*node)->length;
 189                *len  -= (*node)->length;
 190        }
 191
 192        if (ret == EFI_DEV_END_ENTIRE)
 193                *len = 0;
 194
 195        return child;
 196}
 197