drivers/platform/chrome/cros_hps_i2c.c

   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(hps->enable_gpio, 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(&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
  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(&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
 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, 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, true);
 127         return 0;
 128 }
 129 static DEFINE_RUNTIME_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" },
 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 = pm_ptr(&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");