Re: [PATCH v2 3/4] staging:iio:ad5933: Report temperature as raw value

[Jonathan Cameron <jic23@kernel.org>]

On 25/09/14 15:27, Lars-Peter Clausen wrote:
> We shouldn't be doing the unit conversion in kernel space. Just report the
> raw value for the property and the scale. Userspace can do the conversion if
> necessary.
> 
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Technically you are allowed to do this under the ABI so I'm a little dubious about
this one except in that the driver has broken for some time an no one has
noticed hence this is unlikely to cause too many problems!

Will need to hold this anyway until after the fixes have gone through..

> ---
> Changes from v1:
> 	* Slightly restructured error path to make it clear that the mutex is
> 	  only unlocked when it was locked before.
> ---
>  drivers/staging/iio/impedance-analyzer/ad5933.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
> index b6bd609..95b17c5 100644
> --- a/drivers/staging/iio/impedance-analyzer/ad5933.c
> +++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
> @@ -113,7 +113,8 @@ static const struct iio_chan_spec ad5933_channels[] = {
>  		.type = IIO_TEMP,
>  		.indexed = 1,
>  		.channel = 0,
> -		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +			BIT(IIO_CHAN_INFO_SCALE),
>  		.address = AD5933_REG_TEMP_DATA,
>  		.scan_index = -1,
>  		.scan_type = {
> @@ -520,12 +521,11 @@ static int ad5933_read_raw(struct iio_dev *indio_dev,
>  {
>  	struct ad5933_state *st = iio_priv(indio_dev);
>  	__be16 dat;
> -	int ret = -EINVAL;
> +	int ret;
>  
> -	mutex_lock(&indio_dev->mlock);
>  	switch (m) {
>  	case IIO_CHAN_INFO_RAW:
> -	case IIO_CHAN_INFO_PROCESSED:
> +		mutex_lock(&indio_dev->mlock);
>  		if (iio_buffer_enabled(indio_dev)) {
>  			ret = -EBUSY;
>  			goto out;
> @@ -543,16 +543,16 @@ static int ad5933_read_raw(struct iio_dev *indio_dev,
>  		if (ret < 0)
>  			goto out;
>  		mutex_unlock(&indio_dev->mlock);
> -		ret = be16_to_cpu(dat);
> -		/* Temp in Milli degrees Celsius */
> -		if (ret < 8192)
> -			*val = ret * 1000 / 32;
> -		else
> -			*val = (ret - 16384) * 1000 / 32;
> +		*val = sign_extend32(be16_to_cpu(dat), 13);
>  
>  		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = 1000;
> +		*val2 = 5;
> +		return IIO_VAL_FRACTIONAL_LOG2;
>  	}
>  
> +	return -EINVAL;
>  out:
>  	mutex_unlock(&indio_dev->mlock);
>  	return ret;
>