linux-kernel - Re: [PATCH v2 3/3] hwmon: tmp401: bail-out from tmp401

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Date:	Thu, 4 Dec 2014 08:25:21 -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>,
	LM Sensors <lm-sensors@...sensors.org>
Subject: Re: [PATCH v2 3/3] hwmon: tmp401: bail-out from tmp401_probe() in
 case of write errors

On Thu, Dec 04, 2014 at 04:22:54PM +0100, Bartosz Golaszewski wrote:
> The return value of i2c_smbus_read_byte_data() is checked in
> tmp401_init_client(), but only a warning is printed and the device is
> registered anyway. This leads to devices being registered even if they
> cannot be physically detected.
> 
> Bail-out from probe in case of write errors and notify the user.
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> ---
>  drivers/hwmon/tmp401.c | 29 ++++++++++++++++++-----------
>  1 file changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/hwmon/tmp401.c b/drivers/hwmon/tmp401.c
> index a5f0973..ce7e579 100644
> --- a/drivers/hwmon/tmp401.c
> +++ b/drivers/hwmon/tmp401.c
> @@ -618,10 +618,10 @@ static const struct attribute_group tmp432_group = {
>   * Begin non sysfs callback code (aka Real code)
>   */
>  
> -static void tmp401_init_client(struct tmp401_data *data,
> -			       struct i2c_client *client)
> +static int tmp401_init_client(struct tmp401_data *data,
> +			      struct i2c_client *client)
>  {
> -	int config, config_orig;
> +	int config, config_orig, status;
>  
>  	/* Set the conversion rate to 2 Hz */
>  	i2c_smbus_write_byte_data(client, TMP401_CONVERSION_RATE_WRITE, 5);
> @@ -629,16 +629,21 @@ static void tmp401_init_client(struct tmp401_data *data,
>  
>  	/* Start conversions (disable shutdown if necessary) */
>  	config = i2c_smbus_read_byte_data(client, TMP401_CONFIG_READ);
> -	if (config < 0) {
> -		dev_warn(&client->dev, "Initialization failed!\n");
> -		return;
> -	}
> +	if (config < 0)
> +		return config;
>  
>  	config_orig = config;
>  	config &= ~TMP401_CONFIG_SHUTDOWN;
>  
> -	if (config != config_orig)
> -		i2c_smbus_write_byte_data(client, TMP401_CONFIG_WRITE, config);
> +	if (config != config_orig) {
> +		status = i2c_smbus_write_byte_data(client,
> +						   TMP401_CONFIG_WRITE,
> +						   config);
> +		if (status < 0)
> +			return status;

Just pre-initialize status to 0 and return status unconditionally.

Thanks,
Guenter
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