Re: [PATCH 2/3] iio: chemical: add support for Sensirion SPS30 sensor

Himanshu Jha
2018-11-25T10:44:43Z

On Sat, Nov 24, 2018 at 11:14:14PM +0100, Tomasz Duszynski wrote:
> Add support for Sensirion SPS30 particulate matter sensor.
>
> Signed-off-by: Tomasz Duszynski <tduszyns@gmail.com>
> ---
> drivers/iio/chemical/Kconfig | 11 ++
> drivers/iio/chemical/Makefile | 1 +
> drivers/iio/chemical/sps30.c | 359 ++++++++++++++++++++++++++++++++++
> 3 files changed, 371 insertions(+)
> create mode 100644 drivers/iio/chemical/sps30.c

[]

> +#define pr_fmt(fmt) "sps30: " fmt

I don't see its usage ?

> +#include <linux/crc8.h>
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/module.h>
> +
> +#define SPS30_CRC8_POLYNOMIAL 0x31
> +
> +/* SPS30 commands */
> +#define SPS30_START_MEAS 0x0010
> +#define SPS30_STOP_MEAS 0x0104
> +#define SPS30_RESET 0xd304
> +#define SPS30_READ_DATA_READY_FLAG 0x0202
> +#define SPS30_READ_DATA 0x0300
> +#define SPS30_READ_SERIAL 0xD033

Could you please put a tab and align these macros.

#define SPS30_START_MEAS 0x0010
#define SPS30_STOP_MEAS 0x0104

> +static int sps30_write_then_read(struct sps30_state *state, u8 *buf,
> + int buf_size, u8 *data, int data_size)
> +{
> + /* every two received data bytes are checksummed */
> + u8 tmp[data_size + data_size / 2];

No VLAs!

https://lore.kernel.org/lkml/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com/

> + int ret, i;
> +
> + /*
> + * Sensor does not support repeated start so instead of
> + * sending two i2c messages in a row we just send one by one.
> + */
> + ret = i2c_master_send(state->client, buf, buf_size);
> + if (ret != buf_size)
> + return ret < 0 ? ret : -EIO;
> +
> + if (!data)
> + return 0;
> +
> + ret = i2c_master_recv(state->client, tmp, sizeof(tmp));
> + if (ret != sizeof(tmp))
> + return ret < 0 ? ret : -EIO;
> +
> + for (i = 0; i < sizeof(tmp); i += 3) {
> + u8 crc = crc8(sps30_crc8_table, &tmp[i], 2, CRC8_INIT_VALUE);
> +
> + if (crc != tmp[i + 2]) {
> + dev_err(&state->client->dev,
> + "data integrity check failed\n");
> + return -EIO;
> + }
> +
> + *data++ = tmp[i];
> + *data++ = tmp[i + 1];
> + }
> +
> + return 0;
> +}
> +
> +static int sps30_do_cmd(struct sps30_state *state, u16 cmd, u8 *data, int size)
> +{
> + /* depending on the command up to 3 bytes may be needed for argument */
> + u8 buf[sizeof(cmd) + 3] = { cmd >> 8, cmd };

This is fine, since sizeof returns constant integer expression.

> + switch (cmd) {
> + case SPS30_START_MEAS:
> + buf[2] = 0x03;
> + buf[3] = 0x00;
> + buf[4] = 0xac; /* precomputed crc */
> + return sps30_write_then_read(state, buf, 5, NULL, 0);
> + case SPS30_STOP_MEAS:
> + case SPS30_RESET:
> + return sps30_write_then_read(state, buf, 2, NULL, 0);
> + case SPS30_READ_DATA_READY_FLAG:
> + case SPS30_READ_DATA:
> + case SPS30_READ_SERIAL:
> + return sps30_write_then_read(state, buf, 2, data, size);
> + default:
> + return -EINVAL;
> + };
> +}

> +static int sps30_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask)
> +{
> + struct sps30_state *state = iio_priv(indio_dev);
> + int ret;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_PROCESSED:
> + switch (chan->type) {
> + case IIO_MASSCONCENTRATION:
> + mutex_lock(&state->lock);
> + switch (chan->channel2) {
> + case IIO_MOD_PM2p5:

I think lock should be placed here

> + ret = sps30_do_meas(state, val, val2);

... and unlock here.

> + break;
> + case IIO_MOD_PM10:
> + ret = sps30_do_meas(state, val2, val);
> + break;
> + default:
> + break;
> + }
> + mutex_unlock(&state->lock);
> + if (ret)
> + return ret;
> +
> + return IIO_VAL_INT;
> + default:
> + return -EINVAL;
> + }
> + break;
> + default:
> + return -EINVAL;
> + }
> +}

[]

> +static int sps30_probe(struct i2c_client *client)
> +{
> + struct iio_dev *indio_dev;
> + struct sps30_state *state;
> + u8 buf[32] = { };

This is not valid in ISO-C but only in C++.

Instead,

u8 buf[32] = {0};

> + int ret;
> +
> + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
> + return -EOPNOTSUPP;
> +
> + indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*state));
> + if (!indio_dev)
> + return -ENOMEM;
> +
> + state = iio_priv(indio_dev);
> + i2c_set_clientdata(client, indio_dev);
> + state->client = client;
> + indio_dev->dev.parent = &client->dev;
> + indio_dev->info = &sps30_info;
> + indio_dev->name = client->name;
> + indio_dev->channels = sps30_channels;
> + indio_dev->num_channels = ARRAY_SIZE(sps30_channels);
> + indio_dev->modes = INDIO_DIRECT_MODE;
> + indio_dev->available_scan_masks = sps30_scan_masks;
> +
> + mutex_init(&state->lock);
> + crc8_populate_msb(sps30_crc8_table, SPS30_CRC8_POLYNOMIAL);
> +
> + /*
> + * Power-on-reset causes sensor to produce some glitch on i2c bus
> + * and some controllers end up in error state. Recover simply
> + * by placing something on the bus.
> + */
> + ret = sps30_do_cmd(state, SPS30_RESET, NULL, 0);
> + if (ret) {
> + dev_err(&client->dev, "failed to reset device\n");
> + return ret;
> + }
> + usleep_range(2500000, 3500000);

Isn't that range too high ?
msleep_interruptible ?

> + sps30_do_cmd(state, SPS30_STOP_MEAS, NULL, 0);
> +
> + ret = sps30_do_cmd(state, SPS30_READ_SERIAL, buf, sizeof(buf));
> + if (ret) {
> + dev_err(&client->dev, "failed to read serial number\n");
> + return ret;
> + }
> + dev_info(&client->dev, "serial number: %s\n", buf);
> +
> + ret = sps30_do_cmd(state, SPS30_START_MEAS, NULL, 0);
> + if (ret) {
> + dev_err(&client->dev, "failed to start measurement\n");
> + return ret;
> + }
> +
> + ret = devm_iio_triggered_buffer_setup(&client->dev, indio_dev, NULL,
> + sps30_trigger_handler, NULL);
> + if (ret)
> + return ret;
> +
> + return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static int sps30_remove(struct i2c_client *client)

Perfect candidate for `devm_add_action_or_reset()` ?

> +{
> + struct iio_dev *indio_dev = i2c_get_clientdata(client);
> + struct sps30_state *state = iio_priv(indio_dev);
> +
> + sps30_do_cmd(state, SPS30_STOP_MEAS, NULL, 0);
> +
> + return 0;
> +}

--
Himanshu Jha
Undergraduate Student
Department of Electronics & Communication
Guru Tegh Bahadur Institute of Technology