Re: [lm-sensors] [PATCH] hwmon: add driver for Microchip TC74

[Guenter Roeck <linux@roeck-us.net>]

On 06/21/2015 05:38 AM, Maciej S. Szmigiero wrote:
> Add hwmon driver for the Microchip TC74.
>
> The TC74 is a single-input 8-bit I2C temperature sensor,
> with +-2 degrees centigrade accuracy.
>
> Signed-off-by: Maciej Szmigiero <mail@maciej.szmigiero.name>
>
> diff --git a/Documentation/hwmon/tc74 b/Documentation/hwmon/tc74
> new file mode 100644
> index 0000000..caecb1f
> --- /dev/null
> +++ b/Documentation/hwmon/tc74
> @@ -0,0 +1,20 @@
> +Kernel driver tc74
> +====================
> +
> +Supported chips:
> +   * Microchip TC74
> +     Prefix: 'tc74'
> +     Datasheet: Publicly available at Microchip website.
> +
> +Description
> +-----------
> +
> +Driver supports the above part.
> +
> +The tc74 has an 8-bit sensor, with 1 degree centigrade resolution
> +and +- 2 degrees centigrade accuracy.
> +
> +Notes
> +-----
> +
> +Currently entering low power standby mode is not supported.
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 25d9e72..bbaaa2e 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1452,6 +1452,16 @@ config SENSORS_INA2XX
>   	  This driver can also be built as a module.  If so, the module
>   	  will be called ina2xx.
>
> +config SENSORS_TC74
> +	tristate "Microchip TC74"
> +	depends on I2C
> +	help
> +	  If you say yes here you get support for Microchip TC74 single
> +	  input temperature sensor chips.
> +
> +	  This driver can also be built as a module.  If so, the module
> +	  will be called tc74.
> +
>   config SENSORS_THMC50
>   	tristate "Texas Instruments THMC50 / Analog Devices ADM1022"
>   	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index b4a40f1..ab90402 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -140,6 +140,7 @@ obj-$(CONFIG_SENSORS_SMSC47B397)+= smsc47b397.o
>   obj-$(CONFIG_SENSORS_SMSC47M1)	+= smsc47m1.o
>   obj-$(CONFIG_SENSORS_SMSC47M192)+= smsc47m192.o
>   obj-$(CONFIG_SENSORS_AMC6821)	+= amc6821.o
> +obj-$(CONFIG_SENSORS_TC74)	+= tc74.o
>   obj-$(CONFIG_SENSORS_THMC50)	+= thmc50.o
>   obj-$(CONFIG_SENSORS_TMP102)	+= tmp102.o
>   obj-$(CONFIG_SENSORS_TMP103)	+= tmp103.o
> diff --git a/drivers/hwmon/tc74.c b/drivers/hwmon/tc74.c
> new file mode 100644
> index 0000000..5000c58
> --- /dev/null
> +++ b/drivers/hwmon/tc74.c
> @@ -0,0 +1,191 @@
> +/*
> + * An hwmon driver for the Microchip TC74
> + *
> + * Copyright 2015 Maciej Szmigiero <mail@maciej.szmigiero.name>
> + *
> + * Based on ad7414.c:
> + *	Copyright 2006 Stefan Roese, DENX Software Engineering
> + *	Copyright 2008 Sean MacLennan, PIKA Technologies
> + *	Copyright 2008 Frank Edelhaeuser, Spansion Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/jiffies.h>
> +#include <linux/i2c.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/err.h>
> +#include <linux/mutex.h>
> +#include <linux/sysfs.h>
> +#include <linux/slab.h>
> +
Include files in alphabetic order, please.

> +/* TC74 registers */
> +#define TC74_REG_TEMP		0x00
> +#define TC74_REG_CONFIG		0x01
> +
> +struct tc74_data {
> +	struct i2c_client	*client;
> +	struct mutex		lock;	/* atomic read data updates */
> +	char			valid;	/* !=0 if following fields are valid */

bool, please, and use true/false.

> +	unsigned long		next_update;	/* In jiffies */
> +	s8			temp_input;	/* Temp value in dC */
> +};
> +
> +static inline s8 tc74_temp_from_reg(s32 reg)
> +{
> +	u8 v8 = reg & 0xff;
> +
> +	return (s8)v8;
> +}
> +
> +static inline s32 tc74_read(struct i2c_client *client, u8 reg)
> +{
> +	return i2c_smbus_read_byte_data(client, reg);
> +}
> +
> +static inline s32 tc74_write(struct i2c_client *client, u8 reg, u8 value)
> +{
> +	return i2c_smbus_write_byte_data(client, reg, value);
> +}
> +
Those three functions are unnecessary; please drop.

> +static int tc74_update_device(struct device *dev)
> +{
> +	struct tc74_data *data = dev_get_drvdata(dev);
> +	struct i2c_client *client = data->client;
> +	int ret;
> +
> +	ret = mutex_lock_interruptible(&data->lock);
> +	if (ret)
> +		return ret;
> +
> +	if (time_after(jiffies, data->next_update) || !data->valid) {
> +		s32 value;
> +
> +		value = tc74_read(client, TC74_REG_CONFIG);
> +		if (value < 0) {
> +			dev_dbg(&client->dev, "TC74_REG_CONFIG read err %d\n",
> +				(int)value);
> +
> +			ret = value;
> +			goto ret_unlock;
> +		}
> +
> +		if (!(value & 1 << 6)) {

Please use BIT().

> +			/* not ready yet */
> +
> +			ret = -EAGAIN;
> +			goto ret_unlock;
> +		}
> +
> +		value = tc74_read(client, TC74_REG_TEMP);
> +		if (value < 0) {
> +			dev_dbg(&client->dev, "TC74_REG_TEMP read err %d\n",
> +				(int)value);
> +
> +			ret = value;
> +			goto ret_unlock;
> +		}
> +
> +		data->temp_input = tc74_temp_from_reg(value);

C handles type conversion automatically, so just assign the value.

> +		data->next_update = jiffies + HZ / 4;
> +		data->valid = 1;
> +	}
> +
> +ret_unlock:
> +	mutex_unlock(&data->lock);
> +
> +	return ret;
> +}
> +
> +static ssize_t show_temp_input(struct device *dev,
> +			       struct device_attribute *attr, char *buf)
> +{
> +	struct tc74_data *data = dev_get_drvdata(dev);
> +	int ret;linux-kernel@vger.kernel.org
> +
???? does this compile ???

> +	ret = tc74_update_device(dev);
> +	if (ret)
> +		return ret;
> +
> +	return sprintf(buf, "%d\n", (int)(data->temp_input) * 1000);

Unnecessary typecast.

> +}
> +static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, show_temp_input, NULL, 0);
> +
> +static struct attribute *tc74_attrs[] = {
> +	&sensor_dev_attr_temp1_input.dev_attr.attr,
> +	NULL
> +};
> +
> +ATTRIBUTE_GROUPS(tc74);
> +
> +static int tc74_probe(struct i2c_client *client,
> +			const struct i2c_device_id *dev_id)
> +{
> +	struct device *dev = &client->dev;
> +	struct tc74_data *data;
> +	struct device *hwmon_dev;
> +	s32 conf;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
> +		return -EOPNOTSUPP;
> +
> +	data = devm_kzalloc(dev, sizeof(struct tc74_data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	data->client = client;
> +	mutex_init(&data->lock);
> +
> +	/* Make sure the chip is powered up. */
> +	conf = tc74_read(client, TC74_REG_CONFIG);
> +	if (conf < 0) {
> +		dev_err(dev, "unable to read config register\n");
> +
> +		return conf;
> +	} else if (conf & 0x3f) {
> +		dev_err(dev, "invalid config register value\n");
> +
> +		return -ENODEV;
> +	} else if (conf & 1 << 7) {

Please use BIT().

The else cases are all not needed.

> +		s32 ret;
> +
> +		conf &= ~(1 << 7);

Please use BIT.

> +
> +		ret = tc74_write(client, TC74_REG_CONFIG, conf);
> +		if (ret)
> +			dev_warn(dev, "unable to disable STANDBY\n");
> +	}
> +
> +	dev_info(&client->dev, "chip found\n");
> +

Unnecessary noise; please drop.

Thanks,
Guenter

> +	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
> +							   client->name,
> +							   data, tc74_groups);
> +	return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct i2c_device_id tc74_id[] = {
> +	{ "tc74", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, tc74_id);
> +
> +static struct i2c_driver tc74_driver = {
> +	.driver = {
> +		.name	= "tc74",
> +	},
> +	.probe	= tc74_probe,
> +	.id_table = tc74_id,
> +};
> +
> +module_i2c_driver(tc74_driver);
> +
> +MODULE_AUTHOR("Maciej Szmigiero <mail@maciej.szmigiero.name>");
> +
> +MODULE_DESCRIPTION("TC74 driver");
> +MODULE_LICENSE("GPL");
>

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