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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * dev-path-parser.c - EFI Device Path parser
4 * Copyright (C) 2016 Lukas Wunner <[email protected]>
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
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 } else
45 *child = &adev->dev;
46
47 return 0;
48}
49
50static int __init match_pci_dev(struct device *dev, const void *data)
51{
52 unsigned int devfn = *(const 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 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
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 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 */
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 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}