Re: [PATCH 1/2] iio: adc: sc27xx: Add raw data support

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 24 Aug 2018 17:53:15 +0800
Baolin Wang <baolin.wang@linaro.org> wrote:

> The headset device will use channel 20 of ADC controller to detect events,
> but it needs the raw ADC data to do conversion according to its own formula.
> 
> Thus we should configure the channel mask separately and configure channel
> 20 as IIO_CHAN_INFO_RAW, as well as adding raw data read support.

So is this a general thing, i.e. that channel is 'meant' to be used for the
headset, or just a one off for a particular board?

If it is a general thing, than I'm fine with this (unlikely we'll break any
other users), but if not we need to find a nicer way to do it.
I am a little unclear on how a channel would provide the voltage on it's pin
but that could be wrong when used for a different purpose?
If it's just a matter of unusual loading characteristics then perhaps that
is valid, but I'd like to understand this a little.

> 
> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> ---
>  drivers/iio/adc/sc27xx_adc.c |   80 ++++++++++++++++++++++++------------------
>  1 file changed, 45 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/iio/adc/sc27xx_adc.c b/drivers/iio/adc/sc27xx_adc.c
> index 2b60efe..153c311 100644
> --- a/drivers/iio/adc/sc27xx_adc.c
> +++ b/drivers/iio/adc/sc27xx_adc.c
> @@ -273,6 +273,17 @@ static int sc27xx_adc_read_raw(struct iio_dev *indio_dev,
>  	int ret, tmp;
>  
>  	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&indio_dev->mlock);
> +		ret = sc27xx_adc_read(data, chan->channel, scale, &tmp);
> +		mutex_unlock(&indio_dev->mlock);
> +
> +		if (ret)
> +			return ret;
> +
> +		*val = tmp;
> +		return IIO_VAL_INT;
> +
>  	case IIO_CHAN_INFO_PROCESSED:
>  		mutex_lock(&indio_dev->mlock);
>  		ret = sc27xx_adc_read_processed(data, chan->channel, scale,
> @@ -315,48 +326,47 @@ static int sc27xx_adc_write_raw(struct iio_dev *indio_dev,
>  	.write_raw = &sc27xx_adc_write_raw,
>  };
>  
> -#define SC27XX_ADC_CHANNEL(index) {				\
> +#define SC27XX_ADC_CHANNEL(index, mask) {			\
>  	.type = IIO_VOLTAGE,					\
>  	.channel = index,					\
> -	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |	\
> -			      BIT(IIO_CHAN_INFO_SCALE),		\
> +	.info_mask_separate = mask | BIT(IIO_CHAN_INFO_SCALE),	\
>  	.datasheet_name = "CH##index",				\
>  	.indexed = 1,						\
>  }
>  
>  static const struct iio_chan_spec sc27xx_channels[] = {
> -	SC27XX_ADC_CHANNEL(0),
> -	SC27XX_ADC_CHANNEL(1),
> -	SC27XX_ADC_CHANNEL(2),
> -	SC27XX_ADC_CHANNEL(3),
> -	SC27XX_ADC_CHANNEL(4),
> -	SC27XX_ADC_CHANNEL(5),
> -	SC27XX_ADC_CHANNEL(6),
> -	SC27XX_ADC_CHANNEL(7),
> -	SC27XX_ADC_CHANNEL(8),
> -	SC27XX_ADC_CHANNEL(9),
> -	SC27XX_ADC_CHANNEL(10),
> -	SC27XX_ADC_CHANNEL(11),
> -	SC27XX_ADC_CHANNEL(12),
> -	SC27XX_ADC_CHANNEL(13),
> -	SC27XX_ADC_CHANNEL(14),
> -	SC27XX_ADC_CHANNEL(15),
> -	SC27XX_ADC_CHANNEL(16),
> -	SC27XX_ADC_CHANNEL(17),
> -	SC27XX_ADC_CHANNEL(18),
> -	SC27XX_ADC_CHANNEL(19),
> -	SC27XX_ADC_CHANNEL(20),
> -	SC27XX_ADC_CHANNEL(21),
> -	SC27XX_ADC_CHANNEL(22),
> -	SC27XX_ADC_CHANNEL(23),
> -	SC27XX_ADC_CHANNEL(24),
> -	SC27XX_ADC_CHANNEL(25),
> -	SC27XX_ADC_CHANNEL(26),
> -	SC27XX_ADC_CHANNEL(27),
> -	SC27XX_ADC_CHANNEL(28),
> -	SC27XX_ADC_CHANNEL(29),
> -	SC27XX_ADC_CHANNEL(30),
> -	SC27XX_ADC_CHANNEL(31),
> +	SC27XX_ADC_CHANNEL(0, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(1, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(2, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(3, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(4, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(5, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(6, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(7, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(8, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(9, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(10, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(11, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(12, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(13, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(14, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(15, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(16, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(17, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(18, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(19, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(20, BIT(IIO_CHAN_INFO_RAW)),
> +	SC27XX_ADC_CHANNEL(21, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(22, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(23, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(24, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(25, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(26, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(27, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(28, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(29, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(30, BIT(IIO_CHAN_INFO_PROCESSED)),
> +	SC27XX_ADC_CHANNEL(31, BIT(IIO_CHAN_INFO_PROCESSED)),
>  };
>  
>  static int sc27xx_adc_enable(struct sc27xx_adc_data *data)