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 struct acpi_hid_uid {
16 struct acpi_device_id hid[2];
17 char uid[11]; /* UINT_MAX + null byte */
18 };
19
20 static int __init match_acpi_dev(struct device *dev, const void *data)
21 {
22 struct acpi_hid_uid hid_uid = *(const struct acpi_hid_uid *)data;
23 struct acpi_device *adev = to_acpi_device(dev);
24
25 if (acpi_match_device_ids(adev, hid_uid.hid))
26 return 0;
27
28 if (adev->pnp.unique_id)
29 return !strcmp(adev->pnp.unique_id, hid_uid.uid);
30 else
31 return !strcmp("0", hid_uid.uid);
32 }
33
34 static long __init parse_acpi_path(struct efi_dev_path *node,
35 struct device *parent, struct device **child)
36 {
37 struct acpi_hid_uid hid_uid = {};
38 struct device *phys_dev;
39
40 if (node->length != 12)
41 return -EINVAL;
42
43 sprintf(hid_uid.hid[0].id, "%c%c%c%04X",
44 'A' + ((node->acpi.hid >> 10) & 0x1f) - 1,
45 'A' + ((node->acpi.hid >> 5) & 0x1f) - 1,
46 'A' + ((node->acpi.hid >> 0) & 0x1f) - 1,
47 node->acpi.hid >> 16);
48 sprintf(hid_uid.uid, "%u", node->acpi.uid);
49
50 *child = bus_find_device(&acpi_bus_type, NULL, &hid_uid,
51 match_acpi_dev);
52 if (!*child)
53 return -ENODEV;
54
55 phys_dev = acpi_get_first_physical_node(to_acpi_device(*child));
56 if (phys_dev) {
57 get_device(phys_dev);
58 put_device(*child);
59 *child = phys_dev;
60 }
61
62 return 0;
63 }
64
65 static int __init match_pci_dev(struct device *dev, void *data)
66 {
67 unsigned int devfn = *(unsigned int *)data;
68
69 return dev_is_pci(dev) && to_pci_dev(dev)->devfn == devfn;
70 }
71
72 static long __init parse_pci_path(struct efi_dev_path *node,
73 struct device *parent, struct device **child)
74 {
75 unsigned int devfn;
76
77 if (node->length != 6)
78 return -EINVAL;
79 if (!parent)
80 return -EINVAL;
81
82 devfn = PCI_DEVFN(node->pci.dev, node->pci.fn);
83
84 *child = device_find_child(parent, &devfn, match_pci_dev);
85 if (!*child)
86 return -ENODEV;
87
88 return 0;
89 }
90
91 /*
92 * Insert parsers for further node types here.
93 *
94 * Each parser takes a pointer to the @node and to the @parent (will be NULL
95 * for the first device path node). If a device corresponding to @node was
96 * found below @parent, its reference count should be incremented and the
97 * device returned in @child.
98 *
99 * The return value should be 0 on success or a negative int on failure.
100 * The special return values 0x01 (EFI_DEV_END_INSTANCE) and 0xFF
101 * (EFI_DEV_END_ENTIRE) signal the end of the device path, only
102 * parse_end_path() is supposed to return this.
103 *
104 * Be sure to validate the node length and contents before commencing the
105 * search for a device.
106 */
107
108 static long __init parse_end_path(struct efi_dev_path *node,
109 struct device *parent, struct device **child)
110 {
111 if (node->length != 4)
112 return -EINVAL;
113 if (node->sub_type != EFI_DEV_END_INSTANCE &&
114 node->sub_type != EFI_DEV_END_ENTIRE)
115 return -EINVAL;
116 if (!parent)
117 return -ENODEV;
118
119 *child = get_device(parent);
120 return node->sub_type;
121 }
122
123 /**
124 * efi_get_device_by_path - find device by EFI Device Path
125 * @node: EFI Device Path
126 * @len: maximum length of EFI Device Path in bytes
127 *
128 * Parse a series of EFI Device Path nodes at @node and find the corresponding
129 * device. If the device was found, its reference count is incremented and a
130 * pointer to it is returned. The caller needs to drop the reference with
131 * put_device() after use. The @node pointer is updated to point to the
132 * location immediately after the "End of Hardware Device Path" node.
133 *
134 * If another Device Path instance follows, @len is decremented by the number
135 * of bytes consumed. Otherwise @len is set to %0.
136 *
137 * If a Device Path node is malformed or its corresponding device is not found,
138 * @node is updated to point to this offending node and an ERR_PTR is returned.
139 *
140 * If @len is initially %0, the function returns %NULL. Thus, to iterate over
141 * all instances in a path, the following idiom may be used:
142 *
143 * while (!IS_ERR_OR_NULL(dev = efi_get_device_by_path(&node, &len))) {
144 * // do something with dev
145 * put_device(dev);
146 * }
147 * if (IS_ERR(dev))
148 * // report error
149 *
150 * Devices can only be found if they're already instantiated. Most buses
151 * instantiate devices in the "subsys" initcall level, hence the earliest
152 * initcall level in which this function should be called is "fs".
153 *
154 * Returns the device on success or
155 * %ERR_PTR(-ENODEV) if no device was found,
156 * %ERR_PTR(-EINVAL) if a node is malformed or exceeds @len,
157 * %ERR_PTR(-ENOTSUPP) if support for a node type is not yet implemented.
158 */
159 struct device * __init efi_get_device_by_path(struct efi_dev_path **node,
160 size_t *len)
161 {
162 struct device *parent = NULL, *child;
163 long ret = 0;
164
165 if (!*len)
166 return NULL;
167
168 while (!ret) {
169 if (*len < 4 || *len < (*node)->length)
170 ret = -EINVAL;
171 else if ((*node)->type == EFI_DEV_ACPI &&
172 (*node)->sub_type == EFI_DEV_BASIC_ACPI)
173 ret = parse_acpi_path(*node, parent, &child);
174 else if ((*node)->type == EFI_DEV_HW &&
175 (*node)->sub_type == EFI_DEV_PCI)
176 ret = parse_pci_path(*node, parent, &child);
177 else if (((*node)->type == EFI_DEV_END_PATH ||
178 (*node)->type == EFI_DEV_END_PATH2))
179 ret = parse_end_path(*node, parent, &child);
180 else
181 ret = -ENOTSUPP;
182
183 put_device(parent);
184 if (ret < 0)
185 return ERR_PTR(ret);
186
187 parent = child;
188 *node = (void *)*node + (*node)->length;
189 *len -= (*node)->length;
190 }
191
192 if (ret == EFI_DEV_END_ENTIRE)
193 *len = 0;
194
195 return child;
196 }