1/*
  2 * dev-path-parser.c - EFI Device Path parser
  3 * Copyright (C) 2016 Lukas Wunner <lukas@wunner.de>
  4 *
  5 * This program is free software; you can redistribute it and/or modify
  6 * it under the terms of the GNU General Public License (version 2) as
  7 * published by the Free Software Foundation.
  8 *
  9 * This program is distributed in the hope that it will be useful,
 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12 * GNU General Public License for more details.
 13 *
 14 * You should have received a copy of the GNU General Public License
 15 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 16 */
 17
 18#include <linux/acpi.h>
 19#include <linux/efi.h>
 20#include <linux/pci.h>
 21
 22struct acpi_hid_uid {
 23	struct acpi_device_id hid[2];
 24	char uid[11]; /* UINT_MAX + null byte */
 25};
 26
 27static int __init match_acpi_dev(struct device *dev, void *data)
 28{
 29	struct acpi_hid_uid hid_uid = *(struct acpi_hid_uid *)data;
 30	struct acpi_device *adev = to_acpi_device(dev);
 31
 32	if (acpi_match_device_ids(adev, hid_uid.hid))
 33		return 0;
 34
 35	if (adev->pnp.unique_id)
 36		return !strcmp(adev->pnp.unique_id, hid_uid.uid);
 37	else
 38		return !strcmp("0", hid_uid.uid);
 39}
 40
 41static long __init parse_acpi_path(struct efi_dev_path *node,
 42				   struct device *parent, struct device **child)
 43{
 44	struct acpi_hid_uid hid_uid = {};
 45	struct device *phys_dev;
 46
 47	if (node->length != 12)
 48		return -EINVAL;
 49
 50	sprintf(hid_uid.hid[0].id, "%c%c%c%04X",
 51		'A' + ((node->acpi.hid >> 10) & 0x1f) - 1,
 52		'A' + ((node->acpi.hid >>  5) & 0x1f) - 1,
 53		'A' + ((node->acpi.hid >>  0) & 0x1f) - 1,
 54			node->acpi.hid >> 16);
 55	sprintf(hid_uid.uid, "%u", node->acpi.uid);
 56
 57	*child = bus_find_device(&acpi_bus_type, NULL, &hid_uid,
 58				 match_acpi_dev);
 59	if (!*child)
 60		return -ENODEV;
 61
 62	phys_dev = acpi_get_first_physical_node(to_acpi_device(*child));
 63	if (phys_dev) {
 64		get_device(phys_dev);
 65		put_device(*child);
 66		*child = phys_dev;
 67	}
 68
 69	return 0;
 70}
 71
 72static int __init match_pci_dev(struct device *dev, void *data)
 73{
 74	unsigned int devfn = *(unsigned int *)data;
 75
 76	return dev_is_pci(dev) && to_pci_dev(dev)->devfn == devfn;
 77}
 78
 79static long __init parse_pci_path(struct efi_dev_path *node,
 80				  struct device *parent, struct device **child)
 81{
 82	unsigned int devfn;
 83
 84	if (node->length != 6)
 85		return -EINVAL;
 86	if (!parent)
 87		return -EINVAL;
 88
 89	devfn = PCI_DEVFN(node->pci.dev, node->pci.fn);
 90
 91	*child = device_find_child(parent, &devfn, match_pci_dev);
 92	if (!*child)
 93		return -ENODEV;
 94
 95	return 0;
 96}
 97
 98/*
 99 * Insert parsers for further node types here.
100 *
101 * Each parser takes a pointer to the @node and to the @parent (will be NULL
102 * for the first device path node). If a device corresponding to @node was
103 * found below @parent, its reference count should be incremented and the
104 * device returned in @child.
105 *
106 * The return value should be 0 on success or a negative int on failure.
107 * The special return values 0x01 (EFI_DEV_END_INSTANCE) and 0xFF
108 * (EFI_DEV_END_ENTIRE) signal the end of the device path, only
109 * parse_end_path() is supposed to return this.
110 *
111 * Be sure to validate the node length and contents before commencing the
112 * search for a device.
113 */
114
115static long __init parse_end_path(struct efi_dev_path *node,
116				  struct device *parent, struct device **child)
117{
118	if (node->length != 4)
119		return -EINVAL;
120	if (node->sub_type != EFI_DEV_END_INSTANCE &&
121	    node->sub_type != EFI_DEV_END_ENTIRE)
122		return -EINVAL;
123	if (!parent)
124		return -ENODEV;
125
126	*child = get_device(parent);
127	return node->sub_type;
128}
129
130/**
131 * efi_get_device_by_path - find device by EFI Device Path
132 * @node: EFI Device Path
133 * @len: maximum length of EFI Device Path in bytes
134 *
135 * Parse a series of EFI Device Path nodes at @node and find the corresponding
136 * device.  If the device was found, its reference count is incremented and a
137 * pointer to it is returned.  The caller needs to drop the reference with
138 * put_device() after use.  The @node pointer is updated to point to the
139 * location immediately after the "End of Hardware Device Path" node.
140 *
141 * If another Device Path instance follows, @len is decremented by the number
142 * of bytes consumed.  Otherwise @len is set to %0.
143 *
144 * If a Device Path node is malformed or its corresponding device is not found,
145 * @node is updated to point to this offending node and an ERR_PTR is returned.
146 *
147 * If @len is initially %0, the function returns %NULL.  Thus, to iterate over
148 * all instances in a path, the following idiom may be used:
149 *
150 *	while (!IS_ERR_OR_NULL(dev = efi_get_device_by_path(&node, &len))) {
151 *		// do something with dev
152 *		put_device(dev);
153 *	}
154 *	if (IS_ERR(dev))
155 *		// report error
156 *
157 * Devices can only be found if they're already instantiated. Most buses
158 * instantiate devices in the "subsys" initcall level, hence the earliest
159 * initcall level in which this function should be called is "fs".
160 *
161 * Returns the device on success or
162 *	%ERR_PTR(-ENODEV) if no device was found,
163 *	%ERR_PTR(-EINVAL) if a node is malformed or exceeds @len,
164 *	%ERR_PTR(-ENOTSUPP) if support for a node type is not yet implemented.
165 */
166struct device * __init efi_get_device_by_path(struct efi_dev_path **node,
167					      size_t *len)
168{
169	struct device *parent = NULL, *child;
170	long ret = 0;
171
172	if (!*len)
173		return NULL;
174
175	while (!ret) {
176		if (*len < 4 || *len < (*node)->length)
177			ret = -EINVAL;
178		else if ((*node)->type     == EFI_DEV_ACPI &&
179			 (*node)->sub_type == EFI_DEV_BASIC_ACPI)
180			ret = parse_acpi_path(*node, parent, &child);
181		else if ((*node)->type     == EFI_DEV_HW &&
182			 (*node)->sub_type == EFI_DEV_PCI)
183			ret = parse_pci_path(*node, parent, &child);
184		else if (((*node)->type    == EFI_DEV_END_PATH ||
185			  (*node)->type    == EFI_DEV_END_PATH2))
186			ret = parse_end_path(*node, parent, &child);
187		else
188			ret = -ENOTSUPP;
189
190		put_device(parent);
191		if (ret < 0)
192			return ERR_PTR(ret);
193
194		parent = child;
195		*node  = (void *)*node + (*node)->length;
196		*len  -= (*node)->length;
197	}
198
199	if (ret == EFI_DEV_END_ENTIRE)
200		*len = 0;
201
202	return child;
203}