summaryrefslogtreecommitdiffstats
path: root/drivers/firmware/efi/dev-path-parser.c
blob: 20123384271c8150e969471ee19ac090953207d6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
// SPDX-License-Identifier: GPL-2.0
/*
 * dev-path-parser.c - EFI Device Path parser
 * Copyright (C) 2016 Lukas Wunner <lukas@wunner.de>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License (version 2) as
 * published by the Free Software Foundation.
 */

#include <linux/acpi.h>
#include <linux/efi.h>
#include <linux/pci.h>

struct acpi_hid_uid {
	struct acpi_device_id hid[2];
	char uid[11]; /* UINT_MAX + null byte */
};

static int __init match_acpi_dev(struct device *dev, const void *data)
{
	struct acpi_hid_uid hid_uid = *(const struct acpi_hid_uid *)data;
	struct acpi_device *adev = to_acpi_device(dev);

	if (acpi_match_device_ids(adev, hid_uid.hid))
		return 0;

	if (adev->pnp.unique_id)
		return !strcmp(adev->pnp.unique_id, hid_uid.uid);
	else
		return !strcmp("0", hid_uid.uid);
}

static long __init parse_acpi_path(struct efi_dev_path *node,
				   struct device *parent, struct device **child)
{
	struct acpi_hid_uid hid_uid = {};
	struct device *phys_dev;

	if (node->length != 12)
		return -EINVAL;

	sprintf(hid_uid.hid[0].id, "%c%c%c%04X",
		'A' + ((node->acpi.hid >> 10) & 0x1f) - 1,
		'A' + ((node->acpi.hid >>  5) & 0x1f) - 1,
		'A' + ((node->acpi.hid >>  0) & 0x1f) - 1,
			node->acpi.hid >> 16);
	sprintf(hid_uid.uid, "%u", node->acpi.uid);

	*child = bus_find_device(&acpi_bus_type, NULL, &hid_uid,
				 match_acpi_dev);
	if (!*child)
		return -ENODEV;

	phys_dev = acpi_get_first_physical_node(to_acpi_device(*child));
	if (phys_dev) {
		get_device(phys_dev);
		put_device(*child);
		*child = phys_dev;
	}

	return 0;
}

static int __init match_pci_dev(struct device *dev, void *data)
{
	unsigned int devfn = *(unsigned int *)data;

	return dev_is_pci(dev) && to_pci_dev(dev)->devfn == devfn;
}

static long __init parse_pci_path(struct efi_dev_path *node,
				  struct device *parent, struct device **child)
{
	unsigned int devfn;

	if (node->length != 6)
		return -EINVAL;
	if (!parent)
		return -EINVAL;

	devfn = PCI_DEVFN(node->pci.dev, node->pci.fn);

	*child = device_find_child(parent, &devfn, match_pci_dev);
	if (!*child)
		return -ENODEV;

	return 0;
}

/*
 * Insert parsers for further node types here.
 *
 * Each parser takes a pointer to the @node and to the @parent (will be NULL
 * for the first device path node). If a device corresponding to @node was
 * found below @parent, its reference count should be incremented and the
 * device returned in @child.
 *
 * The return value should be 0 on success or a negative int on failure.
 * The special return values 0x01 (EFI_DEV_END_INSTANCE) and 0xFF
 * (EFI_DEV_END_ENTIRE) signal the end of the device path, only
 * parse_end_path() is supposed to return this.
 *
 * Be sure to validate the node length and contents before commencing the
 * search for a device.
 */

static long __init parse_end_path(struct efi_dev_path *node,
				  struct device *parent, struct device **child)
{
	if (node->length != 4)
		return -EINVAL;
	if (node->sub_type != EFI_DEV_END_INSTANCE &&
	    node->sub_type != EFI_DEV_END_ENTIRE)
		return -EINVAL;
	if (!parent)
		return -ENODEV;

	*child = get_device(parent);
	return node->sub_type;
}

/**
 * efi_get_device_by_path - find device by EFI Device Path
 * @node: EFI Device Path
 * @len: maximum length of EFI Device Path in bytes
 *
 * Parse a series of EFI Device Path nodes at @node and find the corresponding
 * device.  If the device was found, its reference count is incremented and a
 * pointer to it is returned.  The caller needs to drop the reference with
 * put_device() after use.  The @node pointer is updated to point to the
 * location immediately after the "End of Hardware Device Path" node.
 *
 * If another Device Path instance follows, @len is decremented by the number
 * of bytes consumed.  Otherwise @len is set to %0.
 *
 * If a Device Path node is malformed or its corresponding device is not found,
 * @node is updated to point to this offending node and an ERR_PTR is returned.
 *
 * If @len is initially %0, the function returns %NULL.  Thus, to iterate over
 * all instances in a path, the following idiom may be used:
 *
 *	while (!IS_ERR_OR_NULL(dev = efi_get_device_by_path(&node, &len))) {
 *		// do something with dev
 *		put_device(dev);
 *	}
 *	if (IS_ERR(dev))
 *		// report error
 *
 * Devices can only be found if they're already instantiated. Most buses
 * instantiate devices in the "subsys" initcall level, hence the earliest
 * initcall level in which this function should be called is "fs".
 *
 * Returns the device on success or
 *	%ERR_PTR(-ENODEV) if no device was found,
 *	%ERR_PTR(-EINVAL) if a node is malformed or exceeds @len,
 *	%ERR_PTR(-ENOTSUPP) if support for a node type is not yet implemented.
 */
struct device * __init efi_get_device_by_path(struct efi_dev_path **node,
					      size_t *len)
{
	struct device *parent = NULL, *child;
	long ret = 0;

	if (!*len)
		return NULL;

	while (!ret) {
		if (*len < 4 || *len < (*node)->length)
			ret = -EINVAL;
		else if ((*node)->type     == EFI_DEV_ACPI &&
			 (*node)->sub_type == EFI_DEV_BASIC_ACPI)
			ret = parse_acpi_path(*node, parent, &child);
		else if ((*node)->type     == EFI_DEV_HW &&
			 (*node)->sub_type == EFI_DEV_PCI)
			ret = parse_pci_path(*node, parent, &child);
		else if (((*node)->type    == EFI_DEV_END_PATH ||
			  (*node)->type    == EFI_DEV_END_PATH2))
			ret = parse_end_path(*node, parent, &child);
		else
			ret = -ENOTSUPP;

		put_device(parent);
		if (ret < 0)
			return ERR_PTR(ret);

		parent = child;
		*node  = (void *)*node + (*node)->length;
		*len  -= (*node)->length;
	}

	if (ret == EFI_DEV_END_ENTIRE)
		*len = 0;

	return child;
}