Re: [PATCH 2/5] iio: adc: ad7192: Add update_scan_mode

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 10 Nov 2021 13:17:47 +0200
<alexandru.tachici@analog.com> wrote:

> From: Alexandru Tachici <alexandru.tachici@analog.com>
> 
> In continuous mode neither sigma_delta.c nor ad7192.c
> will disable previously enabled channels.
> 
> Before this patch a channel stayed enabled indefinetly,
> even when one another one was supposed to be sampled.
> This causes mixed samples in continuous mode to be delivered
> to the host.

Can you expand a bit on the path that leads to this.  As far as I can tell
in both continuous mode enable and single channel reading set_channel()
callback is called and will overwrite the channels enabled previously.

Perhaps I'm missing a path in which that call isn't made?
> 
> By adding an update_scan_mode callback, every time the
> continuous mode is activated, channels will be enabled/disabled
> accordingly.
> 
> Fixes: 3f7c3306cf38 ("staging:iio:ad7192: Use common Sigma Delta library")
> Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
> ---
>  drivers/iio/adc/ad7192.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/iio/adc/ad7192.c b/drivers/iio/adc/ad7192.c
> index 2121a812b0c3..1fc0f4eb858e 100644
> --- a/drivers/iio/adc/ad7192.c
> +++ b/drivers/iio/adc/ad7192.c
> @@ -782,6 +782,20 @@ static int ad7192_read_avail(struct iio_dev *indio_dev,
>  	return -EINVAL;
>  }
>  
> +static int ad7192_update_scan_mode(struct iio_dev *indio_dev, const unsigned long *scan_mask)
> +{
> +	struct ad7192_state *st = iio_priv(indio_dev);
> +	int i;
> +
> +	st->conf &= ~AD7192_CONF_CHAN_MASK;
> +	for (i = 0; i < 8; i++) {
> +		if (test_bit(i, scan_mask))

for_each_set_bit()

> +			st->conf |= AD7192_CONF_CHAN(i);
> +	}
> +
> +	return ad_sd_write_reg(&st->sd, AD7192_REG_CONF, 3, st->conf);
> +}
> +
>  static const struct iio_info ad7192_info = {
>  	.read_raw = ad7192_read_raw,
>  	.write_raw = ad7192_write_raw,
> @@ -789,6 +803,7 @@ static const struct iio_info ad7192_info = {
>  	.read_avail = ad7192_read_avail,
>  	.attrs = &ad7192_attribute_group,
>  	.validate_trigger = ad_sd_validate_trigger,
> +	.update_scan_mode = ad7192_update_scan_mode,
>  };
>  
>  static const struct iio_info ad7195_info = {
> @@ -798,6 +813,7 @@ static const struct iio_info ad7195_info = {
>  	.read_avail = ad7192_read_avail,
>  	.attrs = &ad7195_attribute_group,
>  	.validate_trigger = ad_sd_validate_trigger,
> +	.update_scan_mode = ad7192_update_scan_mode,
>  };
>  
>  #define __AD719x_CHANNEL(_si, _channel1, _channel2, _address, _extend_name, \