1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Dell WMI descriptor driver
4  *
5  * Copyright (C) 2017 Dell Inc. All Rights Reserved.
6  */
7 
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 
10 #include <linux/acpi.h>
11 #include <linux/list.h>
12 #include <linux/module.h>
13 #include <linux/wmi.h>
14 #include "dell-wmi-descriptor.h"
15 
16 #define DELL_WMI_DESCRIPTOR_GUID "8D9DDCBC-A997-11DA-B012-B622A1EF5492"
17 
18 struct descriptor_priv {
19 	struct list_head list;
20 	u32 interface_version;
21 	u32 size;
22 	u32 hotfix;
23 };
24 static int descriptor_valid = -EPROBE_DEFER;
25 static LIST_HEAD(wmi_list);
26 static DEFINE_MUTEX(list_mutex);
27 
dell_wmi_get_descriptor_valid(void)28 int dell_wmi_get_descriptor_valid(void)
29 {
30 	if (!wmi_has_guid(DELL_WMI_DESCRIPTOR_GUID))
31 		return -ENODEV;
32 
33 	return descriptor_valid;
34 }
35 EXPORT_SYMBOL_GPL(dell_wmi_get_descriptor_valid);
36 
dell_wmi_get_interface_version(u32 * version)37 bool dell_wmi_get_interface_version(u32 *version)
38 {
39 	struct descriptor_priv *priv;
40 	bool ret = false;
41 
42 	mutex_lock(&list_mutex);
43 	priv = list_first_entry_or_null(&wmi_list,
44 					struct descriptor_priv,
45 					list);
46 	if (priv) {
47 		*version = priv->interface_version;
48 		ret = true;
49 	}
50 	mutex_unlock(&list_mutex);
51 	return ret;
52 }
53 EXPORT_SYMBOL_GPL(dell_wmi_get_interface_version);
54 
dell_wmi_get_size(u32 * size)55 bool dell_wmi_get_size(u32 *size)
56 {
57 	struct descriptor_priv *priv;
58 	bool ret = false;
59 
60 	mutex_lock(&list_mutex);
61 	priv = list_first_entry_or_null(&wmi_list,
62 					struct descriptor_priv,
63 					list);
64 	if (priv) {
65 		*size = priv->size;
66 		ret = true;
67 	}
68 	mutex_unlock(&list_mutex);
69 	return ret;
70 }
71 EXPORT_SYMBOL_GPL(dell_wmi_get_size);
72 
dell_wmi_get_hotfix(u32 * hotfix)73 bool dell_wmi_get_hotfix(u32 *hotfix)
74 {
75 	struct descriptor_priv *priv;
76 	bool ret = false;
77 
78 	mutex_lock(&list_mutex);
79 	priv = list_first_entry_or_null(&wmi_list,
80 					struct descriptor_priv,
81 					list);
82 	if (priv) {
83 		*hotfix = priv->hotfix;
84 		ret = true;
85 	}
86 	mutex_unlock(&list_mutex);
87 	return ret;
88 }
89 EXPORT_SYMBOL_GPL(dell_wmi_get_hotfix);
90 
91 /*
92  * Descriptor buffer is 128 byte long and contains:
93  *
94  *       Name             Offset  Length  Value
95  * Vendor Signature          0       4    "DELL"
96  * Object Signature          4       4    " WMI"
97  * WMI Interface Version     8       4    <version>
98  * WMI buffer length        12       4    <length>
99  * WMI hotfix number        16       4    <hotfix>
100  */
dell_wmi_descriptor_probe(struct wmi_device * wdev,const void * context)101 static int dell_wmi_descriptor_probe(struct wmi_device *wdev,
102 				     const void *context)
103 {
104 	union acpi_object *obj = NULL;
105 	struct descriptor_priv *priv;
106 	u32 *buffer;
107 	int ret;
108 
109 	obj = wmidev_block_query(wdev, 0);
110 	if (!obj) {
111 		dev_err(&wdev->dev, "failed to read Dell WMI descriptor\n");
112 		ret = -EIO;
113 		goto out;
114 	}
115 
116 	if (obj->type != ACPI_TYPE_BUFFER) {
117 		dev_err(&wdev->dev, "Dell descriptor has wrong type\n");
118 		ret = -EINVAL;
119 		descriptor_valid = ret;
120 		goto out;
121 	}
122 
123 	/* Although it's not technically a failure, this would lead to
124 	 * unexpected behavior
125 	 */
126 	if (obj->buffer.length != 128) {
127 		dev_err(&wdev->dev,
128 			"Dell descriptor buffer has unexpected length (%d)\n",
129 			obj->buffer.length);
130 		ret = -EINVAL;
131 		descriptor_valid = ret;
132 		goto out;
133 	}
134 
135 	buffer = (u32 *)obj->buffer.pointer;
136 
137 	if (strncmp(obj->string.pointer, "DELL WMI", 8) != 0) {
138 		dev_err(&wdev->dev, "Dell descriptor buffer has invalid signature (%8ph)\n",
139 			buffer);
140 		ret = -EINVAL;
141 		descriptor_valid = ret;
142 		goto out;
143 	}
144 	descriptor_valid = 0;
145 
146 	if (buffer[2] != 0 && buffer[2] != 1)
147 		dev_warn(&wdev->dev, "Dell descriptor buffer has unknown version (%lu)\n",
148 			(unsigned long) buffer[2]);
149 
150 	priv = devm_kzalloc(&wdev->dev, sizeof(struct descriptor_priv),
151 	GFP_KERNEL);
152 
153 	if (!priv) {
154 		ret = -ENOMEM;
155 		goto out;
156 	}
157 
158 	priv->interface_version = buffer[2];
159 	priv->size = buffer[3];
160 	priv->hotfix = buffer[4];
161 	ret = 0;
162 	dev_set_drvdata(&wdev->dev, priv);
163 	mutex_lock(&list_mutex);
164 	list_add_tail(&priv->list, &wmi_list);
165 	mutex_unlock(&list_mutex);
166 
167 	dev_dbg(&wdev->dev, "Detected Dell WMI interface version %lu, buffer size %lu, hotfix %lu\n",
168 		(unsigned long) priv->interface_version,
169 		(unsigned long) priv->size,
170 		(unsigned long) priv->hotfix);
171 
172 out:
173 	kfree(obj);
174 	return ret;
175 }
176 
dell_wmi_descriptor_remove(struct wmi_device * wdev)177 static void dell_wmi_descriptor_remove(struct wmi_device *wdev)
178 {
179 	struct descriptor_priv *priv = dev_get_drvdata(&wdev->dev);
180 
181 	mutex_lock(&list_mutex);
182 	list_del(&priv->list);
183 	mutex_unlock(&list_mutex);
184 }
185 
186 static const struct wmi_device_id dell_wmi_descriptor_id_table[] = {
187 	{ .guid_string = DELL_WMI_DESCRIPTOR_GUID },
188 	{ },
189 };
190 
191 static struct wmi_driver dell_wmi_descriptor_driver = {
192 	.driver = {
193 		.name = "dell-wmi-descriptor",
194 	},
195 	.probe = dell_wmi_descriptor_probe,
196 	.remove = dell_wmi_descriptor_remove,
197 	.id_table = dell_wmi_descriptor_id_table,
198 };
199 
200 module_wmi_driver(dell_wmi_descriptor_driver);
201 
202 MODULE_DEVICE_TABLE(wmi, dell_wmi_descriptor_id_table);
203 MODULE_AUTHOR("Mario Limonciello <mario.limonciello@outlook.com>");
204 MODULE_DESCRIPTION("Dell WMI descriptor driver");
205 MODULE_LICENSE("GPL");
206