1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Driver for the ChromeOS human presence sensor (HPS), attached via I2C.
4 *
5 * The driver exposes HPS as a character device, although currently no read or
6 * write operations are supported. Instead, the driver only controls the power
7 * state of the sensor, keeping it on only while userspace holds an open file
8 * descriptor to the HPS device.
9 *
10 * Copyright 2022 Google LLC.
11 */
12
13#include <linux/acpi.h>
14#include <linux/fs.h>
15#include <linux/gpio/consumer.h>
16#include <linux/i2c.h>
17#include <linux/miscdevice.h>
18#include <linux/module.h>
19#include <linux/pm_runtime.h>
20
21#define HPS_ACPI_ID		"GOOG0020"
22
23struct hps_drvdata {
24	struct i2c_client *client;
25	struct miscdevice misc_device;
26	struct gpio_desc *enable_gpio;
27};
28
29static void hps_set_power(struct hps_drvdata *hps, bool state)
30{
31	gpiod_set_value_cansleep(hps->enable_gpio, state);
32}
33
34static int hps_open(struct inode *inode, struct file *file)
35{
36	struct hps_drvdata *hps = container_of(file->private_data,
37					       struct hps_drvdata, misc_device);
38	struct device *dev = &hps->client->dev;
39
40	return pm_runtime_resume_and_get(dev);
41}
42
43static int hps_release(struct inode *inode, struct file *file)
44{
45	struct hps_drvdata *hps = container_of(file->private_data,
46					       struct hps_drvdata, misc_device);
47	struct device *dev = &hps->client->dev;
48
49	return pm_runtime_put(dev);
50}
51
52static const struct file_operations hps_fops = {
53	.owner = THIS_MODULE,
54	.open = hps_open,
55	.release = hps_release,
56};
57
58static int hps_i2c_probe(struct i2c_client *client)
59{
60	struct hps_drvdata *hps;
61	int ret;
62
63	hps = devm_kzalloc(&client->dev, sizeof(*hps), GFP_KERNEL);
64	if (!hps)
65		return -ENOMEM;
66
67	hps->misc_device.parent = &client->dev;
68	hps->misc_device.minor = MISC_DYNAMIC_MINOR;
69	hps->misc_device.name = "cros-hps";
70	hps->misc_device.fops = &hps_fops;
71
72	i2c_set_clientdata(client, hps);
73	hps->client = client;
74
75	/*
76	 * HPS is powered on from firmware before entering the kernel, so we
77	 * acquire the line with GPIOD_OUT_HIGH here to preserve the existing
78	 * state. The peripheral is powered off after successful probe below.
79	 */
80	hps->enable_gpio = devm_gpiod_get(&client->dev, "enable", GPIOD_OUT_HIGH);
81	if (IS_ERR(hps->enable_gpio)) {
82		ret = PTR_ERR(hps->enable_gpio);
83		dev_err(&client->dev, "failed to get enable gpio: %d\n", ret);
84		return ret;
85	}
86
87	ret = misc_register(&hps->misc_device);
88	if (ret) {
89		dev_err(&client->dev, "failed to initialize misc device: %d\n", ret);
90		return ret;
91	}
92
93	hps_set_power(hps, false);
94	pm_runtime_enable(&client->dev);
95	return 0;
96}
97
98static void hps_i2c_remove(struct i2c_client *client)
99{
100	struct hps_drvdata *hps = i2c_get_clientdata(client);
101
102	pm_runtime_disable(&client->dev);
103	misc_deregister(&hps->misc_device);
104
105	/*
106	 * Re-enable HPS, in order to return it to its default state
107	 * (i.e. powered on).
108	 */
109	hps_set_power(hps, true);
110}
111
112static int hps_suspend(struct device *dev)
113{
114	struct i2c_client *client = to_i2c_client(dev);
115	struct hps_drvdata *hps = i2c_get_clientdata(client);
116
117	hps_set_power(hps, false);
118	return 0;
119}
120
121static int hps_resume(struct device *dev)
122{
123	struct i2c_client *client = to_i2c_client(dev);
124	struct hps_drvdata *hps = i2c_get_clientdata(client);
125
126	hps_set_power(hps, true);
127	return 0;
128}
129static UNIVERSAL_DEV_PM_OPS(hps_pm_ops, hps_suspend, hps_resume, NULL);
130
131static const struct i2c_device_id hps_i2c_id[] = {
132	{ "cros-hps", 0 },
133	{ }
134};
135MODULE_DEVICE_TABLE(i2c, hps_i2c_id);
136
137#ifdef CONFIG_ACPI
138static const struct acpi_device_id hps_acpi_id[] = {
139	{ HPS_ACPI_ID, 0 },
140	{ }
141};
142MODULE_DEVICE_TABLE(acpi, hps_acpi_id);
143#endif /* CONFIG_ACPI */
144
145static struct i2c_driver hps_i2c_driver = {
146	.probe = hps_i2c_probe,
147	.remove = hps_i2c_remove,
148	.id_table = hps_i2c_id,
149	.driver = {
150		.name = "cros-hps",
151		.pm = &hps_pm_ops,
152		.acpi_match_table = ACPI_PTR(hps_acpi_id),
153	},
154};
155module_i2c_driver(hps_i2c_driver);
156
157MODULE_ALIAS("acpi:" HPS_ACPI_ID);
158MODULE_AUTHOR("Sami Ky��stil�� <skyostil@chromium.org>");
159MODULE_DESCRIPTION("Driver for ChromeOS HPS");
160MODULE_LICENSE("GPL");
161