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1// SPDX-License-Identifier: GPL-2.02/*3 * dev-path-parser.c - EFI Device Path parser4 * Copyright (C) 2016 Lukas Wunner <lukas@wunner.de>5 *6 * This program is free software; you can redistribute it and/or modify7 * it under the terms of the GNU General Public License (version 2) as8 * published by the Free Software Foundation.9 */10 11#include <linux/acpi.h>12#include <linux/efi.h>13#include <linux/pci.h>14 15static 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 } else45 *child = &adev->dev;46 47 return 0;48}49 50static 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 57static 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 NULL80 * for the first device path node). If a device corresponding to @node was81 * found below @parent, its reference count should be incremented and the82 * 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 0xFF86 * (EFI_DEV_END_ENTIRE) signal the end of the device path, only87 * parse_end_path() is supposed to return this.88 *89 * Be sure to validate the node length and contents before commencing the90 * search for a device.91 */92 93static 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 Path110 * @node: EFI Device Path111 * @len: maximum length of EFI Device Path in bytes112 *113 * Parse a series of EFI Device Path nodes at @node and find the corresponding114 * device. If the device was found, its reference count is incremented and a115 * pointer to it is returned. The caller needs to drop the reference with116 * put_device() after use. The @node pointer is updated to point to the117 * location immediately after the "End of Hardware Device Path" node.118 *119 * If another Device Path instance follows, @len is decremented by the number120 * 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 over126 * 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 dev130 * put_device(dev);131 * }132 * if (IS_ERR(dev))133 * // report error134 *135 * Devices can only be found if they're already instantiated. Most buses136 * instantiate devices in the "subsys" initcall level, hence the earliest137 * initcall level in which this function should be called is "fs".138 *139 * Returns the device on success or140 * %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 */144struct 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 else166 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