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 struct acpi_device *adev;
19 struct device *phys_dev;
20 char hid[ACPI_ID_LEN];
21 u64 uid;
22 int ret;
23
24 if (node->header.length != 12)
25 return -EINVAL;
26
27 sprintf(hid, "%c%c%c%04X",
28 'A' + ((node->acpi.hid >> 10) & 0x1f) - 1,
29 'A' + ((node->acpi.hid >> 5) & 0x1f) - 1,
30 'A' + ((node->acpi.hid >> 0) & 0x1f) - 1,
31 node->acpi.hid >> 16);
32
33 for_each_acpi_dev_match(adev, hid, NULL, -1) {
34 ret = acpi_dev_uid_to_integer(adev, &uid);
35 if (ret == 0 && node->acpi.uid == uid)
36 break;
37 if (ret == -ENODATA && node->acpi.uid == 0)
38 break;
39 }
40 if (!adev)
41 return -ENODEV;
42
43 phys_dev = acpi_get_first_physical_node(adev);
44 if (phys_dev) {
45 *child = get_device(phys_dev);
46 acpi_dev_put(adev);
47 } else
48 *child = &adev->dev;
49
50 return 0;
51 }
52
match_pci_dev(struct device * dev,void * data)53 static int __init match_pci_dev(struct device *dev, void *data)
54 {
55 unsigned int devfn = *(unsigned int *)data;
56
57 return dev_is_pci(dev) && to_pci_dev(dev)->devfn == devfn;
58 }
59
parse_pci_path(const struct efi_dev_path * node,struct device * parent,struct device ** child)60 static long __init parse_pci_path(const struct efi_dev_path *node,
61 struct device *parent, struct device **child)
62 {
63 unsigned int devfn;
64
65 if (node->header.length != 6)
66 return -EINVAL;
67 if (!parent)
68 return -EINVAL;
69
70 devfn = PCI_DEVFN(node->pci.dev, node->pci.fn);
71
72 *child = device_find_child(parent, &devfn, match_pci_dev);
73 if (!*child)
74 return -ENODEV;
75
76 return 0;
77 }
78
79 /*
80 * Insert parsers for further node types here.
81 *
82 * Each parser takes a pointer to the @node and to the @parent (will be NULL
83 * for the first device path node). If a device corresponding to @node was
84 * found below @parent, its reference count should be incremented and the
85 * device returned in @child.
86 *
87 * The return value should be 0 on success or a negative int on failure.
88 * The special return values 0x01 (EFI_DEV_END_INSTANCE) and 0xFF
89 * (EFI_DEV_END_ENTIRE) signal the end of the device path, only
90 * parse_end_path() is supposed to return this.
91 *
92 * Be sure to validate the node length and contents before commencing the
93 * search for a device.
94 */
95
parse_end_path(const struct efi_dev_path * node,struct device * parent,struct device ** child)96 static long __init parse_end_path(const struct efi_dev_path *node,
97 struct device *parent, struct device **child)
98 {
99 if (node->header.length != 4)
100 return -EINVAL;
101 if (node->header.sub_type != EFI_DEV_END_INSTANCE &&
102 node->header.sub_type != EFI_DEV_END_ENTIRE)
103 return -EINVAL;
104 if (!parent)
105 return -ENODEV;
106
107 *child = get_device(parent);
108 return node->header.sub_type;
109 }
110
111 /**
112 * efi_get_device_by_path - find device by EFI Device Path
113 * @node: EFI Device Path
114 * @len: maximum length of EFI Device Path in bytes
115 *
116 * Parse a series of EFI Device Path nodes at @node and find the corresponding
117 * device. If the device was found, its reference count is incremented and a
118 * pointer to it is returned. The caller needs to drop the reference with
119 * put_device() after use. The @node pointer is updated to point to the
120 * location immediately after the "End of Hardware Device Path" node.
121 *
122 * If another Device Path instance follows, @len is decremented by the number
123 * of bytes consumed. Otherwise @len is set to %0.
124 *
125 * If a Device Path node is malformed or its corresponding device is not found,
126 * @node is updated to point to this offending node and an ERR_PTR is returned.
127 *
128 * If @len is initially %0, the function returns %NULL. Thus, to iterate over
129 * all instances in a path, the following idiom may be used:
130 *
131 * while (!IS_ERR_OR_NULL(dev = efi_get_device_by_path(&node, &len))) {
132 * // do something with dev
133 * put_device(dev);
134 * }
135 * if (IS_ERR(dev))
136 * // report error
137 *
138 * Devices can only be found if they're already instantiated. Most buses
139 * instantiate devices in the "subsys" initcall level, hence the earliest
140 * initcall level in which this function should be called is "fs".
141 *
142 * Returns the device on success or
143 * %ERR_PTR(-ENODEV) if no device was found,
144 * %ERR_PTR(-EINVAL) if a node is malformed or exceeds @len,
145 * %ERR_PTR(-ENOTSUPP) if support for a node type is not yet implemented.
146 */
efi_get_device_by_path(const struct efi_dev_path ** node,size_t * len)147 struct device * __init efi_get_device_by_path(const struct efi_dev_path **node,
148 size_t *len)
149 {
150 struct device *parent = NULL, *child;
151 long ret = 0;
152
153 if (!*len)
154 return NULL;
155
156 while (!ret) {
157 if (*len < 4 || *len < (*node)->header.length)
158 ret = -EINVAL;
159 else if ((*node)->header.type == EFI_DEV_ACPI &&
160 (*node)->header.sub_type == EFI_DEV_BASIC_ACPI)
161 ret = parse_acpi_path(*node, parent, &child);
162 else if ((*node)->header.type == EFI_DEV_HW &&
163 (*node)->header.sub_type == EFI_DEV_PCI)
164 ret = parse_pci_path(*node, parent, &child);
165 else if (((*node)->header.type == EFI_DEV_END_PATH ||
166 (*node)->header.type == EFI_DEV_END_PATH2))
167 ret = parse_end_path(*node, parent, &child);
168 else
169 ret = -ENOTSUPP;
170
171 put_device(parent);
172 if (ret < 0)
173 return ERR_PTR(ret);
174
175 parent = child;
176 *node = (void *)*node + (*node)->header.length;
177 *len -= (*node)->header.length;
178 }
179
180 if (ret == EFI_DEV_END_ENTIRE)
181 *len = 0;
182
183 return child;
184 }
185