Re: [PATCH] hwmon: sht4x: Fix sht4x_read_values return value

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

On Sat, May 29, 2021 at 02:13:52AM -0700, Joe Perches wrote:
> Kernel doc for sht4x_read_values() shows 0 on success, 1 on failure but
> the return value on success is actually always positive as it is set to
> SHT4X_RESPONSE_LENGTH by a successful call to i2c_master_recv().
> 
> Miscellanea:
> 
> o Update the kernel doc for sht4x_read_values to 0 for success or -ERRNO
> o Remove incorrectly used kernel doc /** header for other _read functions
> o Typo fix succesfull->successful
> o Reverse a test to unindent a block and use goto unlock
> o Declare cmd[SHT4X_CMD_LEN] rather than cmd[]
> 
> At least for gcc 10.2, object size is reduced a tiny bit.
> 
> $ size drivers/hwmon/sht4x.o*
>    text	   data	    bss	    dec	    hex	filename
>    1752	    404	    256	   2412	    96c	drivers/hwmon/sht4x.o.new
>    1825	    404	    256	   2485	    9b5	drivers/hwmon/sht4x.o.old
> 
> Signed-off-by: Joe Perches <joe@perches.com>

Thanks, applied.

Guenter

> ---
> 
> compiled, untested, no hardware
> 
>  drivers/hwmon/sht4x.c | 95 ++++++++++++++++++++++++---------------------------
>  1 file changed, 45 insertions(+), 50 deletions(-)
> 
> diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c
> index 1dc51ee2a72ba..09c2a0b064444 100644
> --- a/drivers/hwmon/sht4x.c
> +++ b/drivers/hwmon/sht4x.c
> @@ -67,7 +67,7 @@ struct sht4x_data {
>  /**
>   * sht4x_read_values() - read and parse the raw data from the SHT4X
>   * @sht4x_data: the struct sht4x_data to use for the lock
> - * Return: 0 if succesfull, 1 if not
> + * Return: 0 if successful, -ERRNO if not
>   */
>  static int sht4x_read_values(struct sht4x_data *data)
>  {
> @@ -75,51 +75,53 @@ static int sht4x_read_values(struct sht4x_data *data)
>  	u16 t_ticks, rh_ticks;
>  	unsigned long next_update;
>  	struct i2c_client *client = data->client;
> -	u8 crc, raw_data[SHT4X_RESPONSE_LENGTH],
> -	cmd[] = {SHT4X_CMD_MEASURE_HPM};
> +	u8 crc;
> +	u8 cmd[SHT4X_CMD_LEN] = {SHT4X_CMD_MEASURE_HPM};
> +	u8 raw_data[SHT4X_RESPONSE_LENGTH];
>  
>  	mutex_lock(&data->lock);
>  	next_update = data->last_updated +
>  		      msecs_to_jiffies(data->update_interval);
> -	if (!data->valid || time_after(jiffies, next_update)) {
> -		ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN);
> -		if (ret < 0)
> -			goto unlock;
> -
> -		usleep_range(SHT4X_MEAS_DELAY,
> -			     SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA);
> -
> -		ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
> -		if (ret != SHT4X_RESPONSE_LENGTH) {
> -			if (ret >= 0)
> -				ret = -ENODATA;
> -
> -			goto unlock;
> -		}
> -
> -		t_ticks = raw_data[0] << 8 | raw_data[1];
> -		rh_ticks = raw_data[3] << 8 | raw_data[4];
> -
> -		crc = crc8(sht4x_crc8_table, &raw_data[0], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
> -		if (crc != raw_data[2]) {
> -			dev_err(&client->dev, "data integrity check failed\n");
> -			ret = -EIO;
> -			goto unlock;
> -		}
> -
> -		crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
> -		if (crc != raw_data[5]) {
> -			dev_err(&client->dev, "data integrity check failed\n");
> -			ret = -EIO;
> -			goto unlock;
> -		}
> -
> -		data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000;
> -		data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000;
> -		data->last_updated = jiffies;
> -		data->valid = true;
> +
> +	if (data->valid && time_before_eq(jiffies, next_update))
> +		goto unlock;
> +
> +	ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN);
> +	if (ret < 0)
> +		goto unlock;
> +
> +	usleep_range(SHT4X_MEAS_DELAY, SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA);
> +
> +	ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
> +	if (ret != SHT4X_RESPONSE_LENGTH) {
> +		if (ret >= 0)
> +			ret = -ENODATA;
> +		goto unlock;
> +	}
> +
> +	t_ticks = raw_data[0] << 8 | raw_data[1];
> +	rh_ticks = raw_data[3] << 8 | raw_data[4];
> +
> +	crc = crc8(sht4x_crc8_table, &raw_data[0], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
> +	if (crc != raw_data[2]) {
> +		dev_err(&client->dev, "data integrity check failed\n");
> +		ret = -EIO;
> +		goto unlock;
>  	}
>  
> +	crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
> +	if (crc != raw_data[5]) {
> +		dev_err(&client->dev, "data integrity check failed\n");
> +		ret = -EIO;
> +		goto unlock;
> +	}
> +
> +	data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000;
> +	data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000;
> +	data->last_updated = jiffies;
> +	data->valid = true;
> +	ret = 0;
> +
>  unlock:
>  	mutex_unlock(&data->lock);
>  	return ret;
> @@ -132,19 +134,14 @@ static ssize_t sht4x_interval_write(struct sht4x_data *data, long val)
>  	return 0;
>  }
>  
> -/**
> - * sht4x_interval_read() - read the minimum poll interval
> - *			   in milliseconds
> - */
> +/* sht4x_interval_read() - read the minimum poll interval in milliseconds */
>  static size_t sht4x_interval_read(struct sht4x_data *data, long *val)
>  {
>  	*val = data->update_interval;
>  	return 0;
>  }
>  
> -/**
> - * sht4x_temperature1_read() - read the temperature in millidegrees
> - */
> +/* sht4x_temperature1_read() - read the temperature in millidegrees */
>  static int sht4x_temperature1_read(struct sht4x_data *data, long *val)
>  {
>  	int ret;
> @@ -158,9 +155,7 @@ static int sht4x_temperature1_read(struct sht4x_data *data, long *val)
>  	return 0;
>  }
>  
> -/**
> - * sht4x_humidity1_read() - read a relative humidity in millipercent
> - */
> +/* sht4x_humidity1_read() - read a relative humidity in millipercent */
>  static int sht4x_humidity1_read(struct sht4x_data *data, long *val)
>  {
>  	int ret;