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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2025 Akhilesh Patil <akhilesh@ee.iitb.ac.in>
*
* Driver for adp810 pressure and temperature sensor
* Datasheet:
* https://aosong.com/userfiles/files/media/Datasheet%20ADP810-Digital.pdf
*/
#include <linux/array_size.h>
#include <linux/cleanup.h>
#include <linux/crc8.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/dev_printk.h>
#include <linux/errno.h>
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/mutex.h>
#include <linux/types.h>
#include <linux/unaligned.h>
#include <linux/iio/iio.h>
#include <linux/iio/types.h>
/*
* Refer section 5.4 checksum calculation from datasheet.
* This sensor uses CRC polynomial x^8 + x^5 + x^4 + 1 (0x31)
*/
#define ADP810_CRC8_POLYNOMIAL 0x31
DECLARE_CRC8_TABLE(crc_table);
/*
* Buffer declaration which holds 9 bytes of measurement data read
* from the sensor. Use __packed to avoid any paddings, as data sent
* from the sensor is strictly contiguous 9 bytes.
*/
struct adp810_read_buf {
__be16 dp;
u8 dp_crc;
__be16 tmp;
u8 tmp_crc;
__be16 sf;
u8 sf_crc;
} __packed;
struct adp810_data {
struct i2c_client *client;
/* Use lock to synchronize access to device during read sequence */
struct mutex lock;
};
static int adp810_measure(struct adp810_data *data, struct adp810_read_buf *buf)
{
struct i2c_client *client = data->client;
struct device *dev = &client->dev;
int ret;
u8 trig_cmd[2] = {0x37, 0x2d};
/* Send trigger command to the sensor for measurement */
ret = i2c_master_send(client, trig_cmd, sizeof(trig_cmd));
if (ret < 0) {
dev_err(dev, "Error sending trigger command\n");
return ret;
}
if (ret != sizeof(trig_cmd))
return -EIO;
/*
* Wait for the sensor to acquire data. As per datasheet section 5.3.1,
* at least 10ms delay before reading from the sensor is recommended.
* Here, we wait for 20ms to have some safe margin on the top
* of recommendation and to compensate for any possible variations.
*/
msleep(20);
/* Read sensor values */
ret = i2c_master_recv(client, (char *)buf, sizeof(*buf));
if (ret < 0) {
dev_err(dev, "Error reading from sensor\n");
return ret;
}
if (ret != sizeof(*buf))
return -EIO;
/* CRC checks */
crc8_populate_msb(crc_table, ADP810_CRC8_POLYNOMIAL);
if (buf->dp_crc != crc8(crc_table, (u8 *)&buf->dp, 0x2, CRC8_INIT_VALUE)) {
dev_err(dev, "CRC error for pressure\n");
return -EIO;
}
if (buf->tmp_crc != crc8(crc_table, (u8 *)&buf->tmp, 0x2, CRC8_INIT_VALUE)) {
dev_err(dev, "CRC error for temperature\n");
return -EIO;
}
if (buf->sf_crc != crc8(crc_table, (u8 *)&buf->sf, 0x2, CRC8_INIT_VALUE)) {
dev_err(dev, "CRC error for scale\n");
return -EIO;
}
return 0;
}
static int adp810_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long mask)
{
struct adp810_data *data = iio_priv(indio_dev);
struct device *dev = &data->client->dev;
struct adp810_read_buf buf = { };
int ret;
scoped_guard(mutex, &data->lock) {
ret = adp810_measure(data, &buf);
if (ret) {
dev_err(dev, "Failed to read from device\n");
return ret;
}
}
switch (mask) {
case IIO_CHAN_INFO_RAW:
switch (chan->type) {
case IIO_PRESSURE:
*val = get_unaligned_be16(&buf.dp);
return IIO_VAL_INT;
case IIO_TEMP:
*val = get_unaligned_be16(&buf.tmp);
return IIO_VAL_INT;
default:
return -EINVAL;
}
case IIO_CHAN_INFO_SCALE:
switch (chan->type) {
case IIO_PRESSURE:
*val = get_unaligned_be16(&buf.sf);
return IIO_VAL_INT;
case IIO_TEMP:
*val = 200;
return IIO_VAL_INT;
default:
return -EINVAL;
}
default:
return -EINVAL;
}
}
static const struct iio_info adp810_info = {
.read_raw = adp810_read_raw,
};
static const struct iio_chan_spec adp810_channels[] = {
{
.type = IIO_PRESSURE,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
},
{
.type = IIO_TEMP,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
},
};
static int adp810_probe(struct i2c_client *client)
{
struct device *dev = &client->dev;
struct iio_dev *indio_dev;
struct adp810_data *data;
int ret;
indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
if (!indio_dev)
return -ENOMEM;
data = iio_priv(indio_dev);
data->client = client;
ret = devm_mutex_init(dev, &data->lock);
if (ret)
return ret;
indio_dev->name = "adp810";
indio_dev->channels = adp810_channels;
indio_dev->num_channels = ARRAY_SIZE(adp810_channels);
indio_dev->info = &adp810_info;
indio_dev->modes = INDIO_DIRECT_MODE;
ret = devm_iio_device_register(dev, indio_dev);
if (ret)
return dev_err_probe(dev, ret, "Failed to register IIO device\n");
return 0;
}
static const struct i2c_device_id adp810_id_table[] = {
{ "adp810" },
{ }
};
MODULE_DEVICE_TABLE(i2c, adp810_id_table);
static const struct of_device_id adp810_of_table[] = {
{ .compatible = "aosong,adp810" },
{ }
};
MODULE_DEVICE_TABLE(of, adp810_of_table);
static struct i2c_driver adp810_driver = {
.driver = {
.name = "adp810",
.of_match_table = adp810_of_table,
},
.probe = adp810_probe,
.id_table = adp810_id_table,
};
module_i2c_driver(adp810_driver);
MODULE_AUTHOR("Akhilesh Patil <akhilesh@ee.iitb.ac.in>");
MODULE_DESCRIPTION("Driver for Aosong ADP810 sensor");
MODULE_LICENSE("GPL");
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