linux-kernel - Re: [PATCH 6/6] rtc: isl12022: add support for temperature sensor

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Message-ID: <YyHvXh1Zhy/wsHsD@mail.local>
Date:   Wed, 14 Sep 2022 17:12:30 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH 6/6] rtc: isl12022: add support for temperature sensor

On 30/08/2022 12:01:52+0200, Rasmus Villemoes wrote:
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---
>  drivers/rtc/rtc-isl12022.c | 81 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 81 insertions(+)
> 
> diff --git a/drivers/rtc/rtc-isl12022.c b/drivers/rtc/rtc-isl12022.c
> index b295ec92ee17..1bd72f436318 100644
> --- a/drivers/rtc/rtc-isl12022.c
> +++ b/drivers/rtc/rtc-isl12022.c
> @@ -17,6 +17,8 @@
>  #include <linux/of.h>
>  #include <linux/of_device.h>
>  #include <linux/regmap.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>

You should keep that list ordered

>  
>  /* ISL register offsets */
>  #define ISL12022_REG_SC		0x00
> @@ -30,6 +32,9 @@
>  #define ISL12022_REG_SR		0x07
>  #define ISL12022_REG_INT	0x08
>  
> +#define ISL12022_REG_BETA	0x0d
> +#define ISL12022_REG_TEMP_L	0x28
> +
>  /* ISL register bits */
>  #define ISL12022_HR_MIL		(1 << 7)	/* military or 24 hour time */
>  
> @@ -38,6 +43,7 @@
>  
>  #define ISL12022_INT_WRTC	(1 << 6)
>  
> +#define ISL12022_BETA_TSE	(1 << 7)
>  
>  static struct i2c_driver isl12022_driver;
>  
> @@ -48,6 +54,79 @@ struct isl12022 {
>  	bool write_enabled;	/* true if write enable is set */
>  };
>  
> +/*
> + * A user-initiated temperature conversion is not started by this function,
> + * so the temperature is updated once every ~60 seconds.
> + */
> +static int isl12022_hwmon_read_temp(struct device *dev, s32 *mC)
> +{
> +	struct isl12022 *isl12022 = dev_get_drvdata(dev);
> +	struct regmap *regmap = isl12022->regmap;
> +	u8 temp_buf[2];
> +	s32 temp;
> +	int ret;
> +
> +	ret = regmap_bulk_read(regmap, ISL12022_REG_TEMP_L,
> +			       temp_buf, sizeof(temp_buf));
> +	if (ret)
> +		return ret;
> +	/*
> +	 * Temperature is represented as a 10-bit number, unit half-Kelvins.
> +	 */
> +	temp = (temp_buf[1] << 8) | temp_buf[0];
> +	temp *= 500;
> +	temp -= 273000;
> +
> +	*mC = temp;
> +
> +	return 0;
> +}
> +
> +static ssize_t
> +isl12022_hwmon_show_temp(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	int ret;
> +	s32 temp;
> +
> +	ret = isl12022_hwmon_read_temp(dev, &temp);
> +	if (ret)
> +		return ret;
> +
> +	return sprintf(buf, "%d\n", temp);
> +}
> +static SENSOR_DEVICE_ATTR(temp1_input, 0444, isl12022_hwmon_show_temp,
> +			  NULL, 0);
> +
> +static struct attribute *isl12022_hwmon_attrs[] = {
> +	&sensor_dev_attr_temp1_input.dev_attr.attr,
> +	NULL,
> +};
> +ATTRIBUTE_GROUPS(isl12022_hwmon);
> +
> +static void isl12022_hwmon_register(struct device *dev)
> +{
> +	struct isl12022 *isl12022;
> +	struct device *hwmon;
> +	int ret;
> +
> +	if (!IS_REACHABLE(CONFIG_HWMON))
> +		return;
> +
> +	isl12022 = dev_get_drvdata(dev);
> +
> +	ret = regmap_update_bits(isl12022->regmap, ISL12022_REG_BETA,
> +				 ISL12022_BETA_TSE, ISL12022_BETA_TSE);
> +	if (ret) {
> +		dev_warn(dev, "unable to enable temperature sensor\n");
> +		return;
> +	}
> +
> +	hwmon = devm_hwmon_device_register_with_groups(dev, "isl12022", isl12022,
> +						       isl12022_hwmon_groups);
> +	if (IS_ERR(hwmon))
> +		dev_warn(dev, "unable to register hwmon device: %pe\n", hwmon);
> +}
> +
>  /*
>   * In the routines that deal directly with the isl12022 hardware, we use
>   * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch.
> @@ -179,6 +258,8 @@ static int isl12022_probe(struct i2c_client *client)
>  		return PTR_ERR(isl12022->regmap);
>  	}
>  
> +	isl12022_hwmon_register(&client->dev);
> +
>  	isl12022->rtc = devm_rtc_allocate_device(&client->dev);
>  	if (IS_ERR(isl12022->rtc))
>  		return PTR_ERR(isl12022->rtc);
> -- 
> 2.37.2
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com