Re: [PATCH 22/22] iio: dac: ad5686: add gain control support

Jonathan Cameron
2026-04-23T18:29:56Z

On Wed, 22 Apr 2026 15:45:56 +0100
Rodrigo Alencar via B4 Relay <devnull+rodrigo.alencar.analog.com@kernel.org> wrote:

> From: Rodrigo Alencar <rodrigo.alencar@analog.com>
>
> Most of the supported devices rely on a GAIN pin to control a 2x
> multiplier applied to the output voltage. Other devices, e.g. the
> single-channel ones, provides a gain control through a bit field in the
> control register. Some designs might have the GAIN pin hardwired to
> VDD/VLOGIC or GND, which would still be fine for this patch, that allows
> the scale property to be configurable with two available options. In
> read_raw() and write_raw() implementations mutex guards are used to allow
> early returns.
>
> Signed-off-by: Rodrigo Alencar <rodrigo.alencar@analog.com>
Minor stuff inline.

Thanks,

Jonathan

> ---
> drivers/iio/dac/ad5686.c | 110 +++++++++++++++++++++++++++++++++++++++--------
> drivers/iio/dac/ad5686.h | 8 ++++
> 2 files changed, 101 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/iio/dac/ad5686.c b/drivers/iio/dac/ad5686.c
> index bec951afe8d0..adbf62848697 100644
> --- a/drivers/iio/dac/ad5686.c
> +++ b/drivers/iio/dac/ad5686.c

> static inline int ad5686_pd_mask_shift(const struct iio_chan_spec *chan)
> @@ -163,20 +167,25 @@ static int ad5686_read_raw(struct iio_dev *indio_dev,
> struct ad5686_state *st = iio_priv(indio_dev);
> int ret;
>
> + guard(mutex)(&st->lock);
As below. I'd break out the guard() usage as a precusor cleanup patch.

> +
> switch (m) {
> case IIO_CHAN_INFO_RAW:
> - mutex_lock(&st->lock);
> ret = ad5686_read(st, chan->address);
> - mutex_unlock(&st->lock);
> if (ret < 0)
> return ret;
> *val = (ret >> chan->scan_type.shift) &
> GENMASK(chan->scan_type.realbits - 1, 0);
> return IIO_VAL_INT;
> case IIO_CHAN_INFO_SCALE:
> - *val = st->vref_mv;
> - *val2 = chan->scan_type.realbits;
> - return IIO_VAL_FRACTIONAL_LOG2;
> + if (st->double_scale) {
> + *val = st->scale_avail[2];
> + *val2 = st->scale_avail[3];
> + } else {
> + *val = st->scale_avail[0];
> + *val2 = st->scale_avail[1];
> + }
> + return IIO_VAL_INT_PLUS_NANO;
> }
> return -EINVAL;
> }
> @@ -188,28 +197,77 @@ static int ad5686_write_raw(struct iio_dev *indio_dev,
> long mask)
> {
> struct ad5686_state *st = iio_priv(indio_dev);
> - int ret;
> +
> + guard(mutex)(&st->lock);
>
> switch (mask) {
> case IIO_CHAN_INFO_RAW:
> if (!in_range(val, 0, 1 << chan->scan_type.realbits))
> return -EINVAL;
>
> - mutex_lock(&st->lock);
> - ret = ad5686_write(st, AD5686_CMD_WRITE_INPUT_N_UPDATE_N,
> - chan->address, val << chan->scan_type.shift);
> - mutex_unlock(&st->lock);

As Andy pointed out, move this switch to guard() magic earlier in series.

> - break;
> - default:
> - ret = -EINVAL;
> - }
> + return ad5686_write(st, AD5686_CMD_WRITE_INPUT_N_UPDATE_N,
> + chan->address, val << chan->scan_type.shift);
> + case IIO_CHAN_INFO_SCALE:
> + if (val == st->scale_avail[0] && val2 == st->scale_avail[1])
> + st->double_scale = false;
> + else if (val == st->scale_avail[2] && val2 == st->scale_avail[3])
> + st->double_scale = true;
> + else
> + return -EINVAL;
>
> - return ret;
> + switch (st->chip_info->regmap_type) {
> + case AD5310_REGMAP:
> + return ad5310_control_sync(st);
> + case AD5683_REGMAP:
> + return ad5683_control_sync(st);
> + case AD5686_REGMAP:
> + gpiod_set_value_cansleep(st->gain_gpio, st->double_scale);
> + return 0;
> + default:
> + return -EINVAL;
> + }
> + default:
> + return -EINVAL;
> + }
> +}
>