1/*
  2 * Dell WMI descriptor driver
  3 *
  4 * Copyright (C) 2017 Dell Inc. All Rights Reserved.
  5 *
  6 *  This program is free software; you can redistribute it and/or modify it
  7 *  under the terms of the GNU General Public License version 2 as published
  8 *  by the Free Software Foundation.
  9 *
 10 *  This program is distributed in the hope that it will be useful,
 11 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 12 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 13 *  GNU General Public License for more details.
 14 */
 15
 16#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 17
 18#include <linux/acpi.h>
 19#include <linux/list.h>
 20#include <linux/module.h>
 21#include <linux/wmi.h>
 22#include "dell-wmi-descriptor.h"
 23
 24#define DELL_WMI_DESCRIPTOR_GUID "8D9DDCBC-A997-11DA-B012-B622A1EF5492"
 25
 26struct descriptor_priv {
 27	struct list_head list;
 28	u32 interface_version;
 29	u32 size;
 30	u32 hotfix;
 31};
 32static int descriptor_valid = -EPROBE_DEFER;
 33static LIST_HEAD(wmi_list);
 34static DEFINE_MUTEX(list_mutex);
 35
 36int dell_wmi_get_descriptor_valid(void)
 37{
 38	if (!wmi_has_guid(DELL_WMI_DESCRIPTOR_GUID))
 39		return -ENODEV;
 40
 41	return descriptor_valid;
 42}
 43EXPORT_SYMBOL_GPL(dell_wmi_get_descriptor_valid);
 44
 45bool dell_wmi_get_interface_version(u32 *version)
 46{
 47	struct descriptor_priv *priv;
 48	bool ret = false;
 49
 50	mutex_lock(&list_mutex);
 51	priv = list_first_entry_or_null(&wmi_list,
 52					struct descriptor_priv,
 53					list);
 54	if (priv) {
 55		*version = priv->interface_version;
 56		ret = true;
 57	}
 58	mutex_unlock(&list_mutex);
 59	return ret;
 60}
 61EXPORT_SYMBOL_GPL(dell_wmi_get_interface_version);
 62
 63bool dell_wmi_get_size(u32 *size)
 64{
 65	struct descriptor_priv *priv;
 66	bool ret = false;
 67
 68	mutex_lock(&list_mutex);
 69	priv = list_first_entry_or_null(&wmi_list,
 70					struct descriptor_priv,
 71					list);
 72	if (priv) {
 73		*size = priv->size;
 74		ret = true;
 75	}
 76	mutex_unlock(&list_mutex);
 77	return ret;
 78}
 79EXPORT_SYMBOL_GPL(dell_wmi_get_size);
 80
 81bool dell_wmi_get_hotfix(u32 *hotfix)
 82{
 83	struct descriptor_priv *priv;
 84	bool ret = false;
 85
 86	mutex_lock(&list_mutex);
 87	priv = list_first_entry_or_null(&wmi_list,
 88					struct descriptor_priv,
 89					list);
 90	if (priv) {
 91		*hotfix = priv->hotfix;
 92		ret = true;
 93	}
 94	mutex_unlock(&list_mutex);
 95	return ret;
 96}
 97EXPORT_SYMBOL_GPL(dell_wmi_get_hotfix);
 98
 99/*
100 * Descriptor buffer is 128 byte long and contains:
101 *
102 *       Name             Offset  Length  Value
103 * Vendor Signature          0       4    "DELL"
104 * Object Signature          4       4    " WMI"
105 * WMI Interface Version     8       4    <version>
106 * WMI buffer length        12       4    <length>
107 * WMI hotfix number        16       4    <hotfix>
108 */
109static int dell_wmi_descriptor_probe(struct wmi_device *wdev)
110{
111	union acpi_object *obj = NULL;
112	struct descriptor_priv *priv;
113	u32 *buffer;
114	int ret;
115
116	obj = wmidev_block_query(wdev, 0);
117	if (!obj) {
118		dev_err(&wdev->dev, "failed to read Dell WMI descriptor\n");
119		ret = -EIO;
120		goto out;
121	}
122
123	if (obj->type != ACPI_TYPE_BUFFER) {
124		dev_err(&wdev->dev, "Dell descriptor has wrong type\n");
125		ret = -EINVAL;
126		descriptor_valid = ret;
127		goto out;
128	}
129
130	/* Although it's not technically a failure, this would lead to
131	 * unexpected behavior
132	 */
133	if (obj->buffer.length != 128) {
134		dev_err(&wdev->dev,
135			"Dell descriptor buffer has unexpected length (%d)\n",
136			obj->buffer.length);
137		ret = -EINVAL;
138		descriptor_valid = ret;
139		goto out;
140	}
141
142	buffer = (u32 *)obj->buffer.pointer;
143
144	if (strncmp(obj->string.pointer, "DELL WMI", 8) != 0) {
145		dev_err(&wdev->dev, "Dell descriptor buffer has invalid signature (%8ph)\n",
146			buffer);
147		ret = -EINVAL;
148		descriptor_valid = ret;
149		goto out;
150	}
151	descriptor_valid = 0;
152
153	if (buffer[2] != 0 && buffer[2] != 1)
154		dev_warn(&wdev->dev, "Dell descriptor buffer has unknown version (%lu)\n",
155			(unsigned long) buffer[2]);
156
157	priv = devm_kzalloc(&wdev->dev, sizeof(struct descriptor_priv),
158	GFP_KERNEL);
159
160	if (!priv) {
161		ret = -ENOMEM;
162		goto out;
163	}
164
165	priv->interface_version = buffer[2];
166	priv->size = buffer[3];
167	priv->hotfix = buffer[4];
168	ret = 0;
169	dev_set_drvdata(&wdev->dev, priv);
170	mutex_lock(&list_mutex);
171	list_add_tail(&priv->list, &wmi_list);
172	mutex_unlock(&list_mutex);
173
174	dev_dbg(&wdev->dev, "Detected Dell WMI interface version %lu, buffer size %lu, hotfix %lu\n",
175		(unsigned long) priv->interface_version,
176		(unsigned long) priv->size,
177		(unsigned long) priv->hotfix);
178
179out:
180	kfree(obj);
181	return ret;
182}
183
184static int dell_wmi_descriptor_remove(struct wmi_device *wdev)
185{
186	struct descriptor_priv *priv = dev_get_drvdata(&wdev->dev);
187
188	mutex_lock(&list_mutex);
189	list_del(&priv->list);
190	mutex_unlock(&list_mutex);
191	return 0;
192}
193
194static const struct wmi_device_id dell_wmi_descriptor_id_table[] = {
195	{ .guid_string = DELL_WMI_DESCRIPTOR_GUID },
196	{ },
197};
198
199static struct wmi_driver dell_wmi_descriptor_driver = {
200	.driver = {
201		.name = "dell-wmi-descriptor",
202	},
203	.probe = dell_wmi_descriptor_probe,
204	.remove = dell_wmi_descriptor_remove,
205	.id_table = dell_wmi_descriptor_id_table,
206};
207
208module_wmi_driver(dell_wmi_descriptor_driver);
209
210MODULE_ALIAS("wmi:" DELL_WMI_DESCRIPTOR_GUID);
211MODULE_AUTHOR("Mario Limonciello <mario.limonciello@dell.com>");
212MODULE_DESCRIPTION("Dell WMI descriptor driver");
213MODULE_LICENSE("GPL");