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 | |
23 | struct hps_drvdata { |
24 | struct i2c_client *client; |
25 | struct miscdevice misc_device; |
26 | struct gpio_desc *enable_gpio; |
27 | }; |
28 | |
29 | static void hps_set_power(struct hps_drvdata *hps, bool state) |
30 | { |
31 | gpiod_set_value_cansleep(desc: hps->enable_gpio, value: state); |
32 | } |
33 | |
34 | static 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 | |
43 | static 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 | |
52 | static const struct file_operations hps_fops = { |
53 | .owner = THIS_MODULE, |
54 | .open = hps_open, |
55 | .release = hps_release, |
56 | }; |
57 | |
58 | static int hps_i2c_probe(struct i2c_client *client) |
59 | { |
60 | struct hps_drvdata *hps; |
61 | int ret; |
62 | |
63 | hps = devm_kzalloc(dev: &client->dev, size: 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, data: 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(dev: &client->dev, con_id: "enable" , flags: GPIOD_OUT_HIGH); |
81 | if (IS_ERR(ptr: hps->enable_gpio)) { |
82 | ret = PTR_ERR(ptr: 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(misc: &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, state: false); |
94 | pm_runtime_enable(dev: &client->dev); |
95 | return 0; |
96 | } |
97 | |
98 | static void hps_i2c_remove(struct i2c_client *client) |
99 | { |
100 | struct hps_drvdata *hps = i2c_get_clientdata(client); |
101 | |
102 | pm_runtime_disable(dev: &client->dev); |
103 | misc_deregister(misc: &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, state: true); |
110 | } |
111 | |
112 | static 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, state: false); |
118 | return 0; |
119 | } |
120 | |
121 | static 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, state: true); |
127 | return 0; |
128 | } |
129 | static UNIVERSAL_DEV_PM_OPS(hps_pm_ops, hps_suspend, hps_resume, NULL); |
130 | |
131 | static const struct i2c_device_id hps_i2c_id[] = { |
132 | { "cros-hps" , 0 }, |
133 | { } |
134 | }; |
135 | MODULE_DEVICE_TABLE(i2c, hps_i2c_id); |
136 | |
137 | #ifdef CONFIG_ACPI |
138 | static const struct acpi_device_id hps_acpi_id[] = { |
139 | { HPS_ACPI_ID, 0 }, |
140 | { } |
141 | }; |
142 | MODULE_DEVICE_TABLE(acpi, hps_acpi_id); |
143 | #endif /* CONFIG_ACPI */ |
144 | |
145 | static 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 | }; |
155 | module_i2c_driver(hps_i2c_driver); |
156 | |
157 | MODULE_ALIAS("acpi:" HPS_ACPI_ID); |
158 | MODULE_AUTHOR("Sami Kyöstilä <skyostil@chromium.org>" ); |
159 | MODULE_DESCRIPTION("Driver for ChromeOS HPS" ); |
160 | MODULE_LICENSE("GPL" ); |
161 | |