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