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 } 204