linux-kernel - Re: [PATCH v2 1/2] staging: iio: ad7780: update voltage on read

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Date:   Sun, 28 Oct 2018 15:56:11 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Renato Lui Geh <renatogeh@...il.com>
Cc:     lars@...afoo.de, Michael.Hennerich@...log.com, knaack.h@....de,
        pmeerw@...erw.net, gregkh@...uxfoundation.org,
        alexandru.Ardelean@...log.com, stefan.popa@...log.com,
        giuliano.belinassi@....br, linux-iio@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        kernel-usp@...glegroups.com
Subject: Re: [PATCH v2 1/2] staging: iio: ad7780: update voltage on read

On Thu, 25 Oct 2018 19:30:04 -0300
Renato Lui Geh <renatogeh@...il.com> wrote:

> The ad7780 driver previously did not read the correct device output, as
> it read an outdated value set at initialization. It now updates its
> voltage on read.
> 
> Signed-off-by: Renato Lui Geh <renatogeh@...il.com>
> ---
>  drivers/staging/iio/adc/ad7780.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/staging/iio/adc/ad7780.c b/drivers/staging/iio/adc/ad7780.c
> index b67412db0318..27972563bb6a 100644
> --- a/drivers/staging/iio/adc/ad7780.c
> +++ b/drivers/staging/iio/adc/ad7780.c
> @@ -87,11 +87,15 @@ static int ad7780_read_raw(struct iio_dev *indio_dev,
>  			   long m)
>  {
>  	struct ad7780_state *st = iio_priv(indio_dev);
> +	int voltage_uv = 0;
No initialization needed as it is always set in the paths where it is used
(before it is used).
>  
>  	switch (m) {
>  	case IIO_CHAN_INFO_RAW:
>  		return ad_sigma_delta_single_conversion(indio_dev, chan, val);
>  	case IIO_CHAN_INFO_SCALE:
> +		voltage_uv = regulator_get_voltage(st->reg);
> +		if (voltage_uv)
> +			st->int_vref_mv = voltage_uv/1000;
>  		*val = st->int_vref_mv * st->gain;
Is there actually a reason (now) to have the stashed value
of int_vref_mv in the state structure?

Also, I think we are always replacing the value that is retrieved
in probe so we can drop reading it there as well.

Thanks,

Jonathan

>  		*val2 = chan->scan_type.realbits - 1;
>  		return IIO_VAL_FRACTIONAL_LOG2;