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