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