Re: [PATCH 3/3] iio: chemical: sgp40: Implement turn_heater_off-command

[Andreas Klinger <ak@it-klinger.de>]

Hi Jaakko,

Jaakko Koivisto <jmatko@utu.fi> schrieb am Fr, 18. Sep 16:40:
> -Turn the heating element off and enter idle mode.
> -Present the functionality as device attribute,
>  'echo 1 > turn_heater_off'.

Instead of introducing a device specific attribute couldn't this be implemented
as standard power management operations (RUNTIME_PM_OPS)?

Andreas

> Saves approx. 2.5 mA compared to regular operation. The heating element
> is automatically turned back on when measurement is performed.
> 
> Signed-off-by: Jaakko Koivisto <jmatko@utu.fi>
> ---
>  drivers/iio/chemical/sgp40.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/drivers/iio/chemical/sgp40.c b/drivers/iio/chemical/sgp40.c
> index 28d5e737d1dc..a4fc5c778303 100644
> --- a/drivers/iio/chemical/sgp40.c
> +++ b/drivers/iio/chemical/sgp40.c
> @@ -29,6 +29,7 @@
>   * by writing to the out values of temp and humidityrelative.
>   */
>  
> +#include "linux/device.h"
>  #include <linux/delay.h>
>  #include <linux/crc8.h>
>  #include <linux/module.h>
> @@ -259,6 +260,21 @@ static int sgp40_execute_self_test(struct sgp40_data *data)
>  	}
>  }
>  
> +static int sgp40_turn_heater_off(struct sgp40_data *data)
> +{
> +	int ret;
> +	struct i2c_client *client = data->client;
> +	struct sgp40_command turn_off = {.command = {0x36, 0x15}};
> +
> +	ret = i2c_master_send(client, (char*)&turn_off, sizeof(turn_off.command));
> +	if (ret != sizeof(turn_off.command)) {
> +		dev_err(data->dev, "i2c_master_send ret: %d, expected %zu", ret, sizeof(turn_off.command));
> +		return -EIO;
> +	}
> +	msleep(1);
> +	return 0;
> +}
> +
>  static int sgp40_measure_resistance_raw(struct sgp40_data *data, u16 *resistance_raw)
>  {
>  	int ret;
> @@ -417,10 +433,22 @@ static ssize_t serial_number_show(struct device *dev,
>  	return sysfs_emit_at(buf, 0, "%llu\n", data->serial_number);
>  }
>  
> +static ssize_t turn_heater_off_store(struct device *dev,
> +				     struct device_attribute *attr,
> +				     const char *buf, size_t len)
> +{
> +	struct sgp40_data *data = iio_priv(dev_to_iio_dev(dev));
> +	sgp40_turn_heater_off(data);
> +
> +	return len;
> +}
> +
>  static IIO_DEVICE_ATTR_RO(serial_number, 0);
> +static IIO_DEVICE_ATTR_WO(turn_heater_off, 0);
>  
>  static struct attribute *sgp40_attributes[] = {
>  	&iio_dev_attr_serial_number.dev_attr.attr,
> +	&iio_dev_attr_turn_heater_off.dev_attr.attr,
>  	NULL
>  };
>  
> -- 
> 2.55.0
>