Re: [PATCH] hwmon: (ad7418) Catch I2C errors

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

On Thu, Feb 07, 2019 at 03:50:36PM -0600, Brandon Maier wrote:
> If there is an i2c failure, the ad7416 reports its temperature as 0C.
> Return an error code so users can properly detect errors.
> 
> Signed-off-by: Brandon Maier <brandon.maier@rockwellcollins.com>

Applied to hwmon-next.

Thanks,
Guenter

> ---
> Tested on an ad7416, attempting to `cat` the temp1_input while the
> sensor is physically disconnected returns this:
> 
> > cat: read error: Remote I/O error
> ---
>  drivers/hwmon/ad7418.c | 65 +++++++++++++++++++++++++++++++-----------
>  1 file changed, 49 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/hwmon/ad7418.c b/drivers/hwmon/ad7418.c
> index 76f0a5c01e8a..28a91d14d7af 100644
> --- a/drivers/hwmon/ad7418.c
> +++ b/drivers/hwmon/ad7418.c
> @@ -54,10 +54,11 @@ struct ad7418_data {
>  	u16			in[4];
>  };
>  
> -static struct ad7418_data *ad7418_update_device(struct device *dev)
> +static int ad7418_update_device(struct device *dev)
>  {
>  	struct ad7418_data *data = dev_get_drvdata(dev);
>  	struct i2c_client *client = data->client;
> +	s32 val;
>  
>  	mutex_lock(&data->lock);
>  
> @@ -67,47 +68,74 @@ static struct ad7418_data *ad7418_update_device(struct device *dev)
>  		int i, ch;
>  
>  		/* read config register and clear channel bits */
> -		cfg = i2c_smbus_read_byte_data(client, AD7418_REG_CONF);
> +		val = i2c_smbus_read_byte_data(client, AD7418_REG_CONF);
> +		if (val < 0)
> +			goto abort;
> +
> +		cfg = val;
>  		cfg &= 0x1F;
>  
> -		i2c_smbus_write_byte_data(client, AD7418_REG_CONF,
> +		val = i2c_smbus_write_byte_data(client, AD7418_REG_CONF,
>  						cfg | AD7418_CH_TEMP);
> +		if (val < 0)
> +			goto abort;
> +
>  		udelay(30);
>  
>  		for (i = 0; i < 3; i++) {
> -			data->temp[i] =
> -				i2c_smbus_read_word_swapped(client,
> -						AD7418_REG_TEMP[i]);
> +			val = i2c_smbus_read_word_swapped(client,
> +							  AD7418_REG_TEMP[i]);
> +			if (val < 0)
> +				goto abort;
> +
> +			data->temp[i] = val;
>  		}
>  
>  		for (i = 0, ch = 4; i < data->adc_max; i++, ch--) {
> -			i2c_smbus_write_byte_data(client,
> -					AD7418_REG_CONF,
> -					cfg | AD7418_REG_ADC_CH(ch));
> +			val = i2c_smbus_write_byte_data(client, AD7418_REG_CONF,
> +					cfg | AD7418_REG_ADC_CH(ch));
> +			if (val < 0)
> +				goto abort;
>  
>  			udelay(15);
> -			data->in[data->adc_max - 1 - i] =
> -				i2c_smbus_read_word_swapped(client,
> -						AD7418_REG_ADC);
> +			val = i2c_smbus_read_word_swapped(client,
> +							  AD7418_REG_ADC);
> +			if (val < 0)
> +				goto abort;
> +
> +			data->in[data->adc_max - 1 - i] = val;
>  		}
>  
>  		/* restore old configuration value */
> -		i2c_smbus_write_word_swapped(client, AD7418_REG_CONF, cfg);
> +		val = i2c_smbus_write_word_swapped(client, AD7418_REG_CONF,
> +						   cfg);
> +		if (val < 0)
> +			goto abort;
>  
>  		data->last_updated = jiffies;
>  		data->valid = 1;
>  	}
>  
>  	mutex_unlock(&data->lock);
> +	return 0;
>  
> -	return data;
> +abort:
> +	data->valid = 0;
> +	mutex_unlock(&data->lock);
> +	return val;
>  }
>  
>  static ssize_t temp_show(struct device *dev, struct device_attribute *devattr,
>  			 char *buf)
>  {
>  	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
> -	struct ad7418_data *data = ad7418_update_device(dev);
> +	struct ad7418_data *data = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = ad7418_update_device(dev);
> +	if (ret < 0)
> +		return ret;
> +
>  	return sprintf(buf, "%d\n",
>  		LM75_TEMP_FROM_REG(data->temp[attr->index]));
>  }
> @@ -116,7 +144,12 @@ static ssize_t adc_show(struct device *dev, struct device_attribute *devattr,
>  			char *buf)
>  {
>  	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
> -	struct ad7418_data *data = ad7418_update_device(dev);
> +	struct ad7418_data *data = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = ad7418_update_device(dev);
> +	if (ret < 0)
> +		return ret;
>  
>  	return sprintf(buf, "%d\n",
>  		((data->in[attr->index] >> 6) * 2500 + 512) / 1024);