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
 18struct descriptor_priv {
 19	struct list_head list;
 20	u32 interface_version;
 21	u32 size;
 22	u32 hotfix;
 23};
 24static int descriptor_valid = -EPROBE_DEFER;
 25static LIST_HEAD(wmi_list);
 26static DEFINE_MUTEX(list_mutex);
 27
 28int 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}
 35EXPORT_SYMBOL_GPL(dell_wmi_get_descriptor_valid);
 36
 37bool 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}
 53EXPORT_SYMBOL_GPL(dell_wmi_get_interface_version);
 54
 55bool 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}
 71EXPORT_SYMBOL_GPL(dell_wmi_get_size);
 72
 73bool 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}
 89EXPORT_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 */
101static 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
172out:
173	kfree(obj);
174	return ret;
175}
176
177static int 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	return 0;
185}
186
187static const struct wmi_device_id dell_wmi_descriptor_id_table[] = {
188	{ .guid_string = DELL_WMI_DESCRIPTOR_GUID },
189	{ },
190};
191
192static struct wmi_driver dell_wmi_descriptor_driver = {
193	.driver = {
194		.name = "dell-wmi-descriptor",
195	},
196	.probe = dell_wmi_descriptor_probe,
197	.remove = dell_wmi_descriptor_remove,
198	.id_table = dell_wmi_descriptor_id_table,
199};
200
201module_wmi_driver(dell_wmi_descriptor_driver);
202
203MODULE_DEVICE_TABLE(wmi, dell_wmi_descriptor_id_table);
204MODULE_AUTHOR("Mario Limonciello <mario.limonciello@dell.com>");
205MODULE_DESCRIPTION("Dell WMI descriptor driver");
206MODULE_LICENSE("GPL");