linux-kernel - Re: [PATCH 1/5] hwmon: ina2xx: bail-out from ina2xx

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Date:	Tue, 25 Nov 2014 07:58:37 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Bartosz Golaszewski <bgolaszewski@...libre.com>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Benoit Cousson <bcousson@...libre.com>,
	Patrick Titiano <ptitiano@...libre.com>
Subject: Re: [PATCH 1/5] hwmon: ina2xx: bail-out from ina2xx_probe() in case
 of configuration errors

On 11/25/2014 07:46 AM, Bartosz Golaszewski wrote:
> The return value of i2c_smbus_write_word_swapped() isn't checked in
> ina2xx_probe(). This leads to devices being registered even if they can not
> be physically detected (e.g. device is not powered-up at boot-time).
>
> Even after restoring power to such device, it is left unconfigured as the
> configuration has never been actually written to the register.
>
> Error out in case of write errors in probe and notify the user.
>
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> ---
>   drivers/hwmon/ina2xx.c | 49 +++++++++++++++++++++++++++++++++++++++++++------
>   1 file changed, 43 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
> index bfd3f3e..660f8ca 100644
> --- a/drivers/hwmon/ina2xx.c
> +++ b/drivers/hwmon/ina2xx.c
> @@ -110,6 +110,40 @@ static const struct ina2xx_config ina2xx_config[] = {
>   	},
>   };
>
> +static int ina2xx_write_register(const struct i2c_client *client,
> +						u8 reg, u16 value)
> +{
> +	return i2c_smbus_write_word_swapped(client, reg, value);
> +}
> +
> +static int ina2xx_configure(const struct i2c_client *client, u16 value)
> +{
> +	int status;
> +
> +	status = ina2xx_write_register(client, INA2XX_CONFIG, value);
> +	if (status < 0) {
> +		dev_err(&client->dev,
> +			"error writing to configuration register: %d\n",
> +			status);
> +	}
> +
> +	return status;
> +}
> +
> +static int ina2xx_calibrate(const struct i2c_client *client, u16 value)
> +{
> +	int status;
> +
> +	status = ina2xx_write_register(client, INA2XX_CALIBRATION, value);
> +	if (status < 0) {
> +		dev_err(&client->dev,
> +			"error writing to calibration register: %d\n",
> +			status);
> +	}
> +
> +	return status;
> +}
> +

You are introducing those two functions with the same code just to display
a different error message. That does not provide enough value to have extra
functions and just increases code size.

Just check the return code from ina2xx_write_register directly in the probe
function and bail out there.

Thanks,
Guenter


>   static struct ina2xx_data *ina2xx_update_device(struct device *dev)
>   {
>   	struct ina2xx_data *data = dev_get_drvdata(dev);
> @@ -247,12 +281,15 @@ static int ina2xx_probe(struct i2c_client *client,
>   	data->config = &ina2xx_config[data->kind];
>
>   	/* device configuration */
> -	i2c_smbus_write_word_swapped(client, INA2XX_CONFIG,
> -				     data->config->config_default);
> -	/* set current LSB to 1mA, shunt is in uOhms */
> -	/* (equation 13 in datasheet) */
> -	i2c_smbus_write_word_swapped(client, INA2XX_CALIBRATION,
> -				     data->config->calibration_factor / shunt);
> +	if (ina2xx_configure(client, data->config->config_default) < 0)
> +		return -ENODEV;
> +
> +	/* Set current LSB to 1mA, shunt is in uOhms
> +	 * (equation 13 in datasheet).
> +	 */
> +	if (ina2xx_calibrate(client,
> +			data->config->calibration_factor / shunt) < 0)
> +		return -ENODEV;
>
>   	data->client = client;
>   	mutex_init(&data->update_lock);
>

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