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Date:   Sun, 31 May 2020 11:02:44 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Tomasz Duszynski <tomasz.duszynski@octakon.com>
Cc:     <linux-iio@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <devicetree@vger.kernel.org>, <robh+dt@kernel.org>,
        <andy.shevchenko@gmail.com>, <pmeerw@pmeerw.net>
Subject: Re: [PATCH v2 2/4] iio: chemical: scd30: add I2C interface driver
Message-ID: <20200531110244.5773908d@archlinux>
In-Reply-To: <20200530213630.87159-3-tomasz.duszynski@octakon.com>
References: <20200530213630.87159-1-tomasz.duszynski@octakon.com>
        <20200530213630.87159-3-tomasz.duszynski@octakon.com>
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On Sat, 30 May 2020 23:36:28 +0200
Tomasz Duszynski <tomasz.duszynski@octakon.com> wrote:

> Add I2C interface driver for the SCD30 sensor.
> 
> Signed-off-by: Tomasz Duszynski <tomasz.duszynski@octakon.com>
Looks good to me.

J
> ---
>  MAINTAINERS                      |   1 +
>  drivers/iio/chemical/Kconfig     |  11 +++
>  drivers/iio/chemical/Makefile    |   1 +
>  drivers/iio/chemical/scd30_i2c.c | 134 +++++++++++++++++++++++++++++++
>  4 files changed, 147 insertions(+)
>  create mode 100644 drivers/iio/chemical/scd30_i2c.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 41a509cca6f1..13aed3473b7e 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -15142,6 +15142,7 @@ M:	Tomasz Duszynski <tomasz.duszynski@octakon.com>
>  S:	Maintained
>  F:	drivers/iio/chemical/scd30.h
>  F:	drivers/iio/chemical/scd30_core.c
> +F:	drivers/iio/chemical/scd30_i2c.c
>  
>  SENSIRION SPS30 AIR POLLUTION SENSOR DRIVER
>  M:	Tomasz Duszynski <tduszyns@gmail.com>
> diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
> index 99e852b67e55..970d34888c2e 100644
> --- a/drivers/iio/chemical/Kconfig
> +++ b/drivers/iio/chemical/Kconfig
> @@ -96,6 +96,17 @@ config SCD30_CORE
>  	  To compile this driver as a module, choose M here: the module will
>  	  be called scd30_core.
>  
> +config SCD30_I2C
> +	tristate "SCD30 carbon dioxide sensor I2C driver"
> +	depends on SCD30_CORE && I2C
> +	select CRC8
> +	help
> +	  Say Y here to build support for the Sensirion SCD30 I2C interface
> +	  driver.
> +
> +	  To compile this driver as a module, choose M here: the module will
> +	  be called scd30_i2c.
> +
>  config SENSIRION_SGP30
>  	tristate "Sensirion SGPxx gas sensors"
>  	depends on I2C
> diff --git a/drivers/iio/chemical/Makefile b/drivers/iio/chemical/Makefile
> index c9804b041ecd..0966ca34e34b 100644
> --- a/drivers/iio/chemical/Makefile
> +++ b/drivers/iio/chemical/Makefile
> @@ -13,6 +13,7 @@ obj-$(CONFIG_CCS811)		+= ccs811.o
>  obj-$(CONFIG_IAQCORE)		+= ams-iaq-core.o
>  obj-$(CONFIG_PMS7003) += pms7003.o
>  obj-$(CONFIG_SCD30_CORE) += scd30_core.o
> +obj-$(CONFIG_SCD30_I2C) += scd30_i2c.o
>  obj-$(CONFIG_SENSIRION_SGP30)	+= sgp30.o
>  obj-$(CONFIG_SPS30) += sps30.o
>  obj-$(CONFIG_VZ89X)		+= vz89x.o
> diff --git a/drivers/iio/chemical/scd30_i2c.c b/drivers/iio/chemical/scd30_i2c.c
> new file mode 100644
> index 000000000000..a6b532b83669
> --- /dev/null
> +++ b/drivers/iio/chemical/scd30_i2c.c
> @@ -0,0 +1,134 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Sensirion SCD30 carbon dioxide sensor i2c driver
> + *
> + * Copyright (c) 2020 Tomasz Duszynski <tomasz.duszynski@octakon.com>
> + *
> + * I2C slave address: 0x61
> + */
> +#include <linux/crc8.h>
> +#include <linux/device.h>
> +#include <linux/errno.h>
> +#include <linux/i2c.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/types.h>
> +#include <asm/unaligned.h>
> +
> +#include "scd30.h"
> +
> +#define SCD30_I2C_MAX_BUF_SIZE 18
> +#define SCD30_I2C_CRC8_POLYNOMIAL 0x31
> +
> +static u16 scd30_i2c_cmd_lookup_tbl[] = {
> +	[CMD_START_MEAS] = 0x0010,
> +	[CMD_STOP_MEAS] = 0x0104,
> +	[CMD_MEAS_INTERVAL] = 0x4600,
> +	[CMD_MEAS_READY] = 0x0202,
> +	[CMD_READ_MEAS] = 0x0300,
> +	[CMD_ASC] = 0x5306,
> +	[CMD_FRC] = 0x5204,
> +	[CMD_TEMP_OFFSET] = 0x5403,
> +	[CMD_FW_VERSION] = 0xd100,
> +	[CMD_RESET] = 0xd304,
> +};
> +
> +DECLARE_CRC8_TABLE(scd30_i2c_crc8_tbl);
> +
> +static int scd30_i2c_xfer(struct scd30_state *state, char *txbuf, int txsize,
> +			  char *rxbuf, int rxsize)
> +{
> +	struct i2c_client *client = to_i2c_client(state->dev);
> +	int ret;
> +
> +	/*
> +	 * repeated start is not supported hence instead of sending two i2c
> +	 * messages in a row we send one by one
> +	 */
> +	ret = i2c_master_send(client, txbuf, txsize);
> +	if (ret != txsize)
> +		return ret < 0 ? ret : -EIO;
> +
> +	if (!rxbuf)
> +		return 0;
> +
> +	ret = i2c_master_recv(client, rxbuf, rxsize);
> +	if (ret != rxsize)
> +		return ret < 0 ? ret : -EIO;
> +
> +	return 0;
> +}
> +
> +static int scd30_i2c_command(struct scd30_state *state, enum scd30_cmd cmd,
> +			     u16 arg, void *response, int size)
> +{
> +	char crc, buf[SCD30_I2C_MAX_BUF_SIZE], *rsp = response;
> +	int i, ret;
> +
> +	put_unaligned_be16(scd30_i2c_cmd_lookup_tbl[cmd], buf);
> +	i = 2;
> +
> +	if (rsp) {
> +		/* each two bytes are followed by a crc8 */
> +		size += size / 2;
> +	} else {
> +		put_unaligned_be16(arg, buf + i);
> +		crc = crc8(scd30_i2c_crc8_tbl, buf + i, 2, CRC8_INIT_VALUE);
> +		i += 2;
> +		buf[i] = crc;
> +		i += 1;
> +
> +		/* commands below don't take an argument */
> +		if ((cmd == CMD_STOP_MEAS) || (cmd == CMD_RESET))
> +			i -= 3;
> +	}
> +
> +	ret = scd30_i2c_xfer(state, buf, i, buf, size);
> +	if (ret)
> +		return ret;
> +
> +	/* validate received data and strip off crc bytes */
> +	for (i = 0; i < size; i += 3) {
> +		crc = crc8(scd30_i2c_crc8_tbl, buf + i, 2, CRC8_INIT_VALUE);
> +		if (crc != buf[i + 2]) {
> +			dev_err(state->dev, "data integrity check failed\n");
> +			return -EIO;
> +		}
> +
> +		*rsp++ = buf[i];
> +		*rsp++ = buf[i + 1];
> +	}
> +
> +	return 0;
> +}
> +
> +static int scd30_i2c_probe(struct i2c_client *client)
> +{
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
> +		return -EOPNOTSUPP;
> +
> +	crc8_populate_msb(scd30_i2c_crc8_tbl, SCD30_I2C_CRC8_POLYNOMIAL);
> +
> +	return scd30_probe(&client->dev, client->irq, client->name, NULL,
> +			   scd30_i2c_command);
> +}
> +
> +static const struct of_device_id scd30_i2c_of_match[] = {
> +	{ .compatible = "sensirion,scd30" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, scd30_i2c_of_match);
> +
> +static struct i2c_driver scd30_i2c_driver = {
> +	.driver = {
> +		.name = KBUILD_MODNAME,
> +		.of_match_table = scd30_i2c_of_match,
> +		.pm = &scd30_pm_ops,
> +	},
> +	.probe_new = scd30_i2c_probe,
> +};
> +module_i2c_driver(scd30_i2c_driver);
> +
> +MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
> +MODULE_DESCRIPTION("Sensirion SCD30 carbon dioxide sensor i2c driver");
> +MODULE_LICENSE("GPL v2");