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 char hid[ACPI_ID_LEN], uid[11]; /* UINT_MAX + null byte */ 19 struct acpi_device *adev; 20 struct device *phys_dev; 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 sprintf(uid, "%u", node->acpi.uid); 31 32 for_each_acpi_dev_match(adev, hid, NULL, -1) { 33 if (adev->pnp.unique_id && !strcmp(adev->pnp.unique_id, uid)) 34 break; 35 if (!adev->pnp.unique_id && node->acpi.uid == 0) 36 break; 37 acpi_dev_put(adev); 38 } 39 if (!adev) 40 return -ENODEV; 41 42 phys_dev = acpi_get_first_physical_node(adev); 43 if (phys_dev) { 44 *child = get_device(phys_dev); 45 acpi_dev_put(adev); 46 } else 47 *child = &adev->dev; 48 49 return 0; 50 } 51 52 static int __init match_pci_dev(struct device *dev, void *data) 53 { 54 unsigned int devfn = *(unsigned int *)data; 55 56 return dev_is_pci(dev) && to_pci_dev(dev)->devfn == devfn; 57 } 58 59 static long __init parse_pci_path(const struct efi_dev_path *node, 60 struct device *parent, struct device **child) 61 { 62 unsigned int devfn; 63 64 if (node->header.length != 6) 65 return -EINVAL; 66 if (!parent) 67 return -EINVAL; 68 69 devfn = PCI_DEVFN(node->pci.dev, node->pci.fn); 70 71 *child = device_find_child(parent, &devfn, match_pci_dev); 72 if (!*child) 73 return -ENODEV; 74 75 return 0; 76 } 77 78 /* 79 * Insert parsers for further node types here. 80 * 81 * Each parser takes a pointer to the @node and to the @parent (will be NULL 82 * for the first device path node). If a device corresponding to @node was 83 * found below @parent, its reference count should be incremented and the 84 * device returned in @child. 85 * 86 * The return value should be 0 on success or a negative int on failure. 87 * The special return values 0x01 (EFI_DEV_END_INSTANCE) and 0xFF 88 * (EFI_DEV_END_ENTIRE) signal the end of the device path, only 89 * parse_end_path() is supposed to return this. 90 * 91 * Be sure to validate the node length and contents before commencing the 92 * search for a device. 93 */ 94 95 static long __init parse_end_path(const struct efi_dev_path *node, 96 struct device *parent, struct device **child) 97 { 98 if (node->header.length != 4) 99 return -EINVAL; 100 if (node->header.sub_type != EFI_DEV_END_INSTANCE && 101 node->header.sub_type != EFI_DEV_END_ENTIRE) 102 return -EINVAL; 103 if (!parent) 104 return -ENODEV; 105 106 *child = get_device(parent); 107 return node->header.sub_type; 108 } 109 110 /** 111 * efi_get_device_by_path - find device by EFI Device Path 112 * @node: EFI Device Path 113 * @len: maximum length of EFI Device Path in bytes 114 * 115 * Parse a series of EFI Device Path nodes at @node and find the corresponding 116 * device. If the device was found, its reference count is incremented and a 117 * pointer to it is returned. The caller needs to drop the reference with 118 * put_device() after use. The @node pointer is updated to point to the 119 * location immediately after the "End of Hardware Device Path" node. 120 * 121 * If another Device Path instance follows, @len is decremented by the number 122 * of bytes consumed. Otherwise @len is set to %0. 123 * 124 * If a Device Path node is malformed or its corresponding device is not found, 125 * @node is updated to point to this offending node and an ERR_PTR is returned. 126 * 127 * If @len is initially %0, the function returns %NULL. Thus, to iterate over 128 * all instances in a path, the following idiom may be used: 129 * 130 * while (!IS_ERR_OR_NULL(dev = efi_get_device_by_path(&node, &len))) { 131 * // do something with dev 132 * put_device(dev); 133 * } 134 * if (IS_ERR(dev)) 135 * // report error 136 * 137 * Devices can only be found if they're already instantiated. Most buses 138 * instantiate devices in the "subsys" initcall level, hence the earliest 139 * initcall level in which this function should be called is "fs". 140 * 141 * Returns the device on success or 142 * %ERR_PTR(-ENODEV) if no device was found, 143 * %ERR_PTR(-EINVAL) if a node is malformed or exceeds @len, 144 * %ERR_PTR(-ENOTSUPP) if support for a node type is not yet implemented. 145 */ 146 struct device * __init efi_get_device_by_path(const struct efi_dev_path **node, 147 size_t *len) 148 { 149 struct device *parent = NULL, *child; 150 long ret = 0; 151 152 if (!*len) 153 return NULL; 154 155 while (!ret) { 156 if (*len < 4 || *len < (*node)->header.length) 157 ret = -EINVAL; 158 else if ((*node)->header.type == EFI_DEV_ACPI && 159 (*node)->header.sub_type == EFI_DEV_BASIC_ACPI) 160 ret = parse_acpi_path(*node, parent, &child); 161 else if ((*node)->header.type == EFI_DEV_HW && 162 (*node)->header.sub_type == EFI_DEV_PCI) 163 ret = parse_pci_path(*node, parent, &child); 164 else if (((*node)->header.type == EFI_DEV_END_PATH || 165 (*node)->header.type == EFI_DEV_END_PATH2)) 166 ret = parse_end_path(*node, parent, &child); 167 else 168 ret = -ENOTSUPP; 169 170 put_device(parent); 171 if (ret < 0) 172 return ERR_PTR(ret); 173 174 parent = child; 175 *node = (void *)*node + (*node)->header.length; 176 *len -= (*node)->header.length; 177 } 178 179 if (ret == EFI_DEV_END_ENTIRE) 180 *len = 0; 181 182 return child; 183 } 184