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 static long __init parse_acpi_path(const struct efi_dev_path *node, 16 struct device *parent, struct device **child) 17 { 18 struct acpi_device *adev; 19 struct device *phys_dev; 20 char hid[ACPI_ID_LEN]; 21 u64 uid; 22 int ret; 23 24 if (node->header.length != 12) 25 return -EINVAL; 26 27 sprintf(hid, "%c%c%c%04X", 28 'A' + ((node->acpi.hid >> 10) & 0x1f) - 1, 29 'A' + ((node->acpi.hid >> 5) & 0x1f) - 1, 30 'A' + ((node->acpi.hid >> 0) & 0x1f) - 1, 31 node->acpi.hid >> 16); 32 33 for_each_acpi_dev_match(adev, hid, NULL, -1) { 34 ret = acpi_dev_uid_to_integer(adev, &uid); 35 if (ret == 0 && node->acpi.uid == uid) 36 break; 37 if (ret == -ENODATA && node->acpi.uid == 0) 38 break; 39 } 40 if (!adev) 41 return -ENODEV; 42 43 phys_dev = acpi_get_first_physical_node(adev); 44 if (phys_dev) { 45 *child = get_device(phys_dev); 46 acpi_dev_put(adev); 47 } else 48 *child = &adev->dev; 49 50 return 0; 51 } 52 53 static int __init match_pci_dev(struct device *dev, void *data) 54 { 55 unsigned int devfn = *(unsigned int *)data; 56 57 return dev_is_pci(dev) && to_pci_dev(dev)->devfn == devfn; 58 } 59 60 static long __init parse_pci_path(const struct efi_dev_path *node, 61 struct device *parent, struct device **child) 62 { 63 unsigned int devfn; 64 65 if (node->header.length != 6) 66 return -EINVAL; 67 if (!parent) 68 return -EINVAL; 69 70 devfn = PCI_DEVFN(node->pci.dev, node->pci.fn); 71 72 *child = device_find_child(parent, &devfn, match_pci_dev); 73 if (!*child) 74 return -ENODEV; 75 76 return 0; 77 } 78 79 /* 80 * Insert parsers for further node types here. 81 * 82 * Each parser takes a pointer to the @node and to the @parent (will be NULL 83 * for the first device path node). If a device corresponding to @node was 84 * found below @parent, its reference count should be incremented and the 85 * device returned in @child. 86 * 87 * The return value should be 0 on success or a negative int on failure. 88 * The special return values 0x01 (EFI_DEV_END_INSTANCE) and 0xFF 89 * (EFI_DEV_END_ENTIRE) signal the end of the device path, only 90 * parse_end_path() is supposed to return this. 91 * 92 * Be sure to validate the node length and contents before commencing the 93 * search for a device. 94 */ 95 96 static long __init parse_end_path(const struct efi_dev_path *node, 97 struct device *parent, struct device **child) 98 { 99 if (node->header.length != 4) 100 return -EINVAL; 101 if (node->header.sub_type != EFI_DEV_END_INSTANCE && 102 node->header.sub_type != EFI_DEV_END_ENTIRE) 103 return -EINVAL; 104 if (!parent) 105 return -ENODEV; 106 107 *child = get_device(parent); 108 return node->header.sub_type; 109 } 110 111 /** 112 * efi_get_device_by_path - find device by EFI Device Path 113 * @node: EFI Device Path 114 * @len: maximum length of EFI Device Path in bytes 115 * 116 * Parse a series of EFI Device Path nodes at @node and find the corresponding 117 * device. If the device was found, its reference count is incremented and a 118 * pointer to it is returned. The caller needs to drop the reference with 119 * put_device() after use. The @node pointer is updated to point to the 120 * location immediately after the "End of Hardware Device Path" node. 121 * 122 * If another Device Path instance follows, @len is decremented by the number 123 * of bytes consumed. Otherwise @len is set to %0. 124 * 125 * If a Device Path node is malformed or its corresponding device is not found, 126 * @node is updated to point to this offending node and an ERR_PTR is returned. 127 * 128 * If @len is initially %0, the function returns %NULL. Thus, to iterate over 129 * all instances in a path, the following idiom may be used: 130 * 131 * while (!IS_ERR_OR_NULL(dev = efi_get_device_by_path(&node, &len))) { 132 * // do something with dev 133 * put_device(dev); 134 * } 135 * if (IS_ERR(dev)) 136 * // report error 137 * 138 * Devices can only be found if they're already instantiated. Most buses 139 * instantiate devices in the "subsys" initcall level, hence the earliest 140 * initcall level in which this function should be called is "fs". 141 * 142 * Returns the device on success or 143 * %ERR_PTR(-ENODEV) if no device was found, 144 * %ERR_PTR(-EINVAL) if a node is malformed or exceeds @len, 145 * %ERR_PTR(-ENOTSUPP) if support for a node type is not yet implemented. 146 */ 147 struct device * __init efi_get_device_by_path(const struct efi_dev_path **node, 148 size_t *len) 149 { 150 struct device *parent = NULL, *child; 151 long ret = 0; 152 153 if (!*len) 154 return NULL; 155 156 while (!ret) { 157 if (*len < 4 || *len < (*node)->header.length) 158 ret = -EINVAL; 159 else if ((*node)->header.type == EFI_DEV_ACPI && 160 (*node)->header.sub_type == EFI_DEV_BASIC_ACPI) 161 ret = parse_acpi_path(*node, parent, &child); 162 else if ((*node)->header.type == EFI_DEV_HW && 163 (*node)->header.sub_type == EFI_DEV_PCI) 164 ret = parse_pci_path(*node, parent, &child); 165 else if (((*node)->header.type == EFI_DEV_END_PATH || 166 (*node)->header.type == EFI_DEV_END_PATH2)) 167 ret = parse_end_path(*node, parent, &child); 168 else 169 ret = -ENOTSUPP; 170 171 put_device(parent); 172 if (ret < 0) 173 return ERR_PTR(ret); 174 175 parent = child; 176 *node = (void *)*node + (*node)->header.length; 177 *len -= (*node)->header.length; 178 } 179 180 if (ret == EFI_DEV_END_ENTIRE) 181 *len = 0; 182 183 return child; 184 } 185