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
  15 struct acpi_hid_uid {
  16         struct acpi_device_id hid[2];
  17         char uid[11]; /* UINT_MAX + null byte */
  18 };
  19
  20 static int __init match_acpi_dev(struct device *dev, void *data)
  21 {
  22         struct acpi_hid_uid hid_uid = *(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
  34 static 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
  65 static 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
  72 static 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
 108 static 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  */
 159 struct 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 }