Re: [PATCH v1 4/5] iio: chemical: add support for winsen MHZ19B CO2 sensor

[Krzysztof Kozlowski <krzk@kernel.org>]

On 03/04/2025 07:32, Gyeyoung Baek wrote:
> Add support for winsen MHZ19B CO2 sensor.
> 
> Datasheet:
> https://www.winsen-sensor.com/d/files/infrared-gas-sensor/mh-z19b-co2-ver1_0.pdf
> 
> Signed-off-by: Gyeyoung Baek <gye976@gmail.com>
> ---
>  drivers/iio/chemical/Kconfig  |  10 +
>  drivers/iio/chemical/Makefile |   1 +
>  drivers/iio/chemical/mhz19b.c | 386 ++++++++++++++++++++++++++++++++++
>  3 files changed, 397 insertions(+)
>  create mode 100644 drivers/iio/chemical/mhz19b.c
> 
> diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
> index 330fe0af946f..bb4dfe3986f6 100644
> --- a/drivers/iio/chemical/Kconfig
> +++ b/drivers/iio/chemical/Kconfig
> @@ -108,6 +108,16 @@ config IAQCORE
>  	  iAQ-Core Continuous/Pulsed VOC (Volatile Organic Compounds)
>  	  sensors
> 
> +config MHZ19B

probably WINSEN_MHZ19B

> +	tristate "MHZ19B CO2 sensor"

Similarly here

> +	depends on SERIAL_DEV_BUS
> +	help
> +	  Say Y here to build Serdev binterface support for the MHZ19B

Typo, interface

> +	  CO2 sensor.
> +
> +	  To compile this driver as a module, choose M here: the module will
> +	  be called mhz19b.
> +
>  config PMS7003
>  	tristate "Plantower PMS7003 particulate matter sensor"
>  	depends on SERIAL_DEV_BUS
> diff --git a/drivers/iio/chemical/Makefile b/drivers/iio/chemical/Makefile
> index 4866db06bdc9..c63daebf39ac 100644
> --- a/drivers/iio/chemical/Makefile
> +++ b/drivers/iio/chemical/Makefile
> @@ -15,6 +15,7 @@ obj-$(CONFIG_ENS160) += ens160_core.o
>  obj-$(CONFIG_ENS160_I2C) += ens160_i2c.o
>  obj-$(CONFIG_ENS160_SPI) += ens160_spi.o
>  obj-$(CONFIG_IAQCORE)		+= ams-iaq-core.o
> +obj-$(CONFIG_MHZ19B) += mhz19b.o
>  obj-$(CONFIG_PMS7003) += pms7003.o
>  obj-$(CONFIG_SCD30_CORE) += scd30_core.o
>  obj-$(CONFIG_SCD30_I2C) += scd30_i2c.o
> diff --git a/drivers/iio/chemical/mhz19b.c b/drivers/iio/chemical/mhz19b.c
> new file mode 100644
> index 000000000000..f8f06c01623f
> --- /dev/null
> +++ b/drivers/iio/chemical/mhz19b.c
> @@ -0,0 +1,386 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * mh-z19b co2 sensor driver
> + *
> + * Copyright (c) 2025 Gyeyoung Baek <gye976@gmail.com>
> + *
> + * Datasheet:
> + * https://www.winsen-sensor.com/d/files/infrared-gas-sensor/mh-z19b-co2-ver1_0.pdf
> + *
> + * TODO:
> + *  - vin supply regulator
> + */
> +
> +#include <linux/cleanup.h>
> +#include <linux/completion.h>
> +#include <linux/device.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/serdev.h>
> +#include <linux/unaligned.h>
> +
> +struct mhz19b_state {
> +	struct serdev_device *serdev;
> +
> +	/* TO DO, nothing for now.*/
> +	struct regulator *vin_supply;

Drop. Don't add dead code.

> +
> +	/* serdev receive buffer.
> +	 * When data is received from the MH-Z19B,
> +	 * the 'mhz19b_receive_buf' callback function is called and fills this buffer.
> +	 */
> +	char buf[9];
> +	int buf_idx;
> +
> +	/* must wait the 'buf' is filled with 9 bytes.*/
> +	struct completion buf_ready;
> +
> +	/* protect access to mhz19b_state */
> +	struct mutex lock;

mhz19b_receive_buf() does not need any locking?


Best regards,
Krzysztof