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

   1 /*
   2  * dev-path-parser.c - EFI Device Path parser
   3  * Copyright (C) 2016 Lukas Wunner <lukas@wunner.de>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License (version 2) as
   7  * published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #include <linux/acpi.h>
  19 #include <linux/efi.h>
  20 #include <linux/pci.h>
  21
  22 struct acpi_hid_uid {
  23         struct acpi_device_id hid[2];
  24         char uid[11]; /* UINT_MAX + null byte */
  25 };
  26
  27 static int __init match_acpi_dev(struct device *dev, void *data)
  28 {
  29         struct acpi_hid_uid hid_uid = *(struct acpi_hid_uid *)data;
  30         struct acpi_device *adev = to_acpi_device(dev);
  31
  32         if (acpi_match_device_ids(adev, hid_uid.hid))
  33                 return 0;
  34
  35         if (adev->pnp.unique_id)
  36                 return !strcmp(adev->pnp.unique_id, hid_uid.uid);
  37         else
  38                 return !strcmp("0", hid_uid.uid);
  39 }
  40
  41 static long __init parse_acpi_path(struct efi_dev_path *node,
  42                                    struct device *parent, struct device **child)
  43 {
  44         struct acpi_hid_uid hid_uid = {};
  45         struct device *phys_dev;
  46
  47         if (node->length != 12)
  48                 return -EINVAL;
  49
  50         sprintf(hid_uid.hid[0].id, "%c%c%c%04X",
  51                 'A' + ((node->acpi.hid >> 10) & 0x1f) - 1,
  52                 'A' + ((node->acpi.hid >>  5) & 0x1f) - 1,
  53                 'A' + ((node->acpi.hid >>  0) & 0x1f) - 1,
  54                         node->acpi.hid >> 16);
  55         sprintf(hid_uid.uid, "%u", node->acpi.uid);
  56
  57         *child = bus_find_device(&acpi_bus_type, NULL, &hid_uid,
  58                                  match_acpi_dev);
  59         if (!*child)
  60                 return -ENODEV;
  61
  62         phys_dev = acpi_get_first_physical_node(to_acpi_device(*child));
  63         if (phys_dev) {
  64                 get_device(phys_dev);
  65                 put_device(*child);
  66                 *child = phys_dev;
  67         }
  68
  69         return 0;
  70 }
  71
  72 static int __init match_pci_dev(struct device *dev, void *data)
  73 {
  74         unsigned int devfn = *(unsigned int *)data;
  75
  76         return dev_is_pci(dev) && to_pci_dev(dev)->devfn == devfn;
  77 }
  78
  79 static long __init parse_pci_path(struct efi_dev_path *node,
  80                                   struct device *parent, struct device **child)
  81 {
  82         unsigned int devfn;
  83
  84         if (node->length != 6)
  85                 return -EINVAL;
  86         if (!parent)
  87                 return -EINVAL;
  88
  89         devfn = PCI_DEVFN(node->pci.dev, node->pci.fn);
  90
  91         *child = device_find_child(parent, &devfn, match_pci_dev);
  92         if (!*child)
  93                 return -ENODEV;
  94
  95         return 0;
  96 }
  97
  98 /*
  99  * Insert parsers for further node types here.
 100  *
 101  * Each parser takes a pointer to the @node and to the @parent (will be NULL
 102  * for the first device path node). If a device corresponding to @node was
 103  * found below @parent, its reference count should be incremented and the
 104  * device returned in @child.
 105  *
 106  * The return value should be 0 on success or a negative int on failure.
 107  * The special return values 0x01 (EFI_DEV_END_INSTANCE) and 0xFF
 108  * (EFI_DEV_END_ENTIRE) signal the end of the device path, only
 109  * parse_end_path() is supposed to return this.
 110  *
 111  * Be sure to validate the node length and contents before commencing the
 112  * search for a device.
 113  */
 114
 115 static long __init parse_end_path(struct efi_dev_path *node,
 116                                   struct device *parent, struct device **child)
 117 {
 118         if (node->length != 4)
 119                 return -EINVAL;
 120         if (node->sub_type != EFI_DEV_END_INSTANCE &&
 121             node->sub_type != EFI_DEV_END_ENTIRE)
 122                 return -EINVAL;
 123         if (!parent)
 124                 return -ENODEV;
 125
 126         *child = get_device(parent);
 127         return node->sub_type;
 128 }
 129
 130 /**
 131  * efi_get_device_by_path - find device by EFI Device Path
 132  * @node: EFI Device Path
 133  * @len: maximum length of EFI Device Path in bytes
 134  *
 135  * Parse a series of EFI Device Path nodes at @node and find the corresponding
 136  * device.  If the device was found, its reference count is incremented and a
 137  * pointer to it is returned.  The caller needs to drop the reference with
 138  * put_device() after use.  The @node pointer is updated to point to the
 139  * location immediately after the "End of Hardware Device Path" node.
 140  *
 141  * If another Device Path instance follows, @len is decremented by the number
 142  * of bytes consumed.  Otherwise @len is set to %0.
 143  *
 144  * If a Device Path node is malformed or its corresponding device is not found,
 145  * @node is updated to point to this offending node and an ERR_PTR is returned.
 146  *
 147  * If @len is initially %0, the function returns %NULL.  Thus, to iterate over
 148  * all instances in a path, the following idiom may be used:
 149  *
 150  *      while (!IS_ERR_OR_NULL(dev = efi_get_device_by_path(&node, &len))) {
 151  *              // do something with dev
 152  *              put_device(dev);
 153  *      }
 154  *      if (IS_ERR(dev))
 155  *              // report error
 156  *
 157  * Devices can only be found if they're already instantiated. Most buses
 158  * instantiate devices in the "subsys" initcall level, hence the earliest
 159  * initcall level in which this function should be called is "fs".
 160  *
 161  * Returns the device on success or
 162  *      %ERR_PTR(-ENODEV) if no device was found,
 163  *      %ERR_PTR(-EINVAL) if a node is malformed or exceeds @len,
 164  *      %ERR_PTR(-ENOTSUPP) if support for a node type is not yet implemented.
 165  */
 166 struct device * __init efi_get_device_by_path(struct efi_dev_path **node,
 167                                               size_t *len)
 168 {
 169         struct device *parent = NULL, *child;
 170         long ret = 0;
 171
 172         if (!*len)
 173                 return NULL;
 174
 175         while (!ret) {
 176                 if (*len < 4 || *len < (*node)->length)
 177                         ret = -EINVAL;
 178                 else if ((*node)->type     == EFI_DEV_ACPI &&
 179                          (*node)->sub_type == EFI_DEV_BASIC_ACPI)
 180                         ret = parse_acpi_path(*node, parent, &child);
 181                 else if ((*node)->type     == EFI_DEV_HW &&
 182                          (*node)->sub_type == EFI_DEV_PCI)
 183                         ret = parse_pci_path(*node, parent, &child);
 184                 else if (((*node)->type    == EFI_DEV_END_PATH ||
 185                           (*node)->type    == EFI_DEV_END_PATH2))
 186                         ret = parse_end_path(*node, parent, &child);
 187                 else
 188                         ret = -ENOTSUPP;
 189
 190                 put_device(parent);
 191                 if (ret < 0)
 192                         return ERR_PTR(ret);
 193
 194                 parent = child;
 195                 *node  = (void *)*node + (*node)->length;
 196                 *len  -= (*node)->length;
 197         }
 198
 199         if (ret == EFI_DEV_END_ENTIRE)
 200                 *len = 0;
 201
 202         return child;
 203 }