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// SPDX-License-Identifier: GPL-2.0
/*
* Driver for the ChromeOS human presence sensor (HPS), attached via I2C.
*
* The driver exposes HPS as a character device, although currently no read or
* write operations are supported. Instead, the driver only controls the power
* state of the sensor, keeping it on only while userspace holds an open file
* descriptor to the HPS device.
*
* Copyright 2022 Google LLC.
*/
#include <linux/acpi.h>
#include <linux/fs.h>
#include <linux/gpio/consumer.h>
#include <linux/i2c.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>
#define HPS_ACPI_ID "GOOG0020"
struct hps_drvdata {
struct i2c_client *client;
struct miscdevice misc_device;
struct gpio_desc *enable_gpio;
};
static void hps_set_power(struct hps_drvdata *hps, bool state)
{
gpiod_set_value_cansleep(hps->enable_gpio, state);
}
static int hps_open(struct inode *inode, struct file *file)
{
struct hps_drvdata *hps = container_of(file->private_data,
struct hps_drvdata, misc_device);
struct device *dev = &hps->client->dev;
return pm_runtime_resume_and_get(dev);
}
static int hps_release(struct inode *inode, struct file *file)
{
struct hps_drvdata *hps = container_of(file->private_data,
struct hps_drvdata, misc_device);
struct device *dev = &hps->client->dev;
return pm_runtime_put(dev);
}
static const struct file_operations hps_fops = {
.owner = THIS_MODULE,
.open = hps_open,
.release = hps_release,
};
static int hps_i2c_probe(struct i2c_client *client)
{
struct hps_drvdata *hps;
int ret;
hps = devm_kzalloc(&client->dev, sizeof(*hps), GFP_KERNEL);
if (!hps)
return -ENOMEM;
hps->misc_device.parent = &client->dev;
hps->misc_device.minor = MISC_DYNAMIC_MINOR;
hps->misc_device.name = "cros-hps";
hps->misc_device.fops = &hps_fops;
i2c_set_clientdata(client, hps);
hps->client = client;
/*
* HPS is powered on from firmware before entering the kernel, so we
* acquire the line with GPIOD_OUT_HIGH here to preserve the existing
* state. The peripheral is powered off after successful probe below.
*/
hps->enable_gpio = devm_gpiod_get(&client->dev, "enable", GPIOD_OUT_HIGH);
if (IS_ERR(hps->enable_gpio)) {
ret = PTR_ERR(hps->enable_gpio);
dev_err(&client->dev, "failed to get enable gpio: %d\n", ret);
return ret;
}
ret = misc_register(&hps->misc_device);
if (ret) {
dev_err(&client->dev, "failed to initialize misc device: %d\n", ret);
return ret;
}
hps_set_power(hps, false);
pm_runtime_enable(&client->dev);
return 0;
}
static void hps_i2c_remove(struct i2c_client *client)
{
struct hps_drvdata *hps = i2c_get_clientdata(client);
pm_runtime_disable(&client->dev);
misc_deregister(&hps->misc_device);
/*
* Re-enable HPS, in order to return it to its default state
* (i.e. powered on).
*/
hps_set_power(hps, true);
}
static int hps_suspend(struct device *dev)
{
struct i2c_client *client = to_i2c_client(dev);
struct hps_drvdata *hps = i2c_get_clientdata(client);
hps_set_power(hps, false);
return 0;
}
static int hps_resume(struct device *dev)
{
struct i2c_client *client = to_i2c_client(dev);
struct hps_drvdata *hps = i2c_get_clientdata(client);
hps_set_power(hps, true);
return 0;
}
static UNIVERSAL_DEV_PM_OPS(hps_pm_ops, hps_suspend, hps_resume, NULL);
static const struct i2c_device_id hps_i2c_id[] = {
{ "cros-hps", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, hps_i2c_id);
#ifdef CONFIG_ACPI
static const struct acpi_device_id hps_acpi_id[] = {
{ HPS_ACPI_ID, 0 },
{ }
};
MODULE_DEVICE_TABLE(acpi, hps_acpi_id);
#endif /* CONFIG_ACPI */
static struct i2c_driver hps_i2c_driver = {
.probe = hps_i2c_probe,
.remove = hps_i2c_remove,
.id_table = hps_i2c_id,
.driver = {
.name = "cros-hps",
.pm = &hps_pm_ops,
.acpi_match_table = ACPI_PTR(hps_acpi_id),
},
};
module_i2c_driver(hps_i2c_driver);
MODULE_ALIAS("acpi:" HPS_ACPI_ID);
MODULE_AUTHOR("Sami Kyöstilä <skyostil@chromium.org>");
MODULE_DESCRIPTION("Driver for ChromeOS HPS");
MODULE_LICENSE("GPL");
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