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Wed, 25 Feb 2026 03:53:12 -0800 (PST) Date: Wed, 25 Feb 2026 08:53:44 -0300 From: Marcelo Schmitt To: Giorgi Tchankvetadze Cc: antoniu.miclaus@analog.com, lars@metafoo.de, Michael.Hennerich@analog.com, jic23@kernel.org, dlechner@baylibre.com, nuno.sa@analog.com, andy@kernel.org, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] iio: adc: ad4030: fix calibscale read/write unit mismatch Message-ID: References: <20260225113102.84568-2-giorgitchankvetadze1997@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260225113102.84568-2-giorgitchankvetadze1997@gmail.com> On 02/25, Giorgi Tchankvetadze wrote: > The read path returns calibscale in IIO_VAL_INT_PLUS_NANO but the write > path treats it as MICRO. Since no write_raw_get_fmt is provided, the > IIO core defaults to MICRO when parsing userspace input. > > This means reading calibscale and writing it back results in a ~1000x > gain error. > > Change the read path and available range to use MICRO to match the > write path. The updates to ad4030 driver will add write_raw_get_fmt() [1]. [1]: https://lore.kernel.org/linux-iio/516cccc47e917bd26be29b016907f50a244a68b9.1771865684.git.marcelo.schmitt@analog.com/ At first glance, I think this could instead add a case to write_raw_get_fmt(), keeping calibscale nano precision (unless nano precision doesn't make sense for ad4030 calibscale (don't recall from top of my mind)). > > Fixes: 0cb8b324852f ("iio: adc: ad4030: add driver for ad4030-24") > Signed-off-by: Giorgi Tchankvetadze > --- > drivers/iio/adc/ad4030.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/iio/adc/ad4030.c b/drivers/iio/adc/ad4030.c > index def3e1d01ceb..3d823648371d 100644 > --- a/drivers/iio/adc/ad4030.c > +++ b/drivers/iio/adc/ad4030.c > @@ -423,10 +423,10 @@ static int ad4030_get_chan_calibscale(struct iio_dev *indio_dev, > > /* From datasheet: multiplied output = input × gain word/0x8000 */ > *val = gain / AD4030_GAIN_MIDLE_POINT; > - *val2 = mul_u64_u32_div(gain % AD4030_GAIN_MIDLE_POINT, NANO, > + *val2 = mul_u64_u32_div(gain % AD4030_GAIN_MIDLE_POINT, MICRO, > AD4030_GAIN_MIDLE_POINT); > > - return IIO_VAL_INT_PLUS_NANO; > + return IIO_VAL_INT_PLUS_MICRO; > } > > /* Returns the offset where 1 LSB = (VREF/2^precision_bits - 1)/gain */ > @@ -720,8 +720,8 @@ static irqreturn_t ad4030_trigger_handler(int irq, void *p) > > static const int ad4030_gain_avail[3][2] = { > { 0, 0 }, > - { 0, 30518 }, > - { 1, 999969482 }, > + { 0, 30 }, > + { 1, 999969 }, > }; > > static int ad4030_read_avail(struct iio_dev *indio_dev, > @@ -739,7 +739,7 @@ static int ad4030_read_avail(struct iio_dev *indio_dev, > > case IIO_CHAN_INFO_CALIBSCALE: > *vals = (void *)ad4030_gain_avail; > - *type = IIO_VAL_INT_PLUS_NANO; > + *type = IIO_VAL_INT_PLUS_MICRO; > return IIO_AVAIL_RANGE; > > case IIO_CHAN_INFO_OVERSAMPLING_RATIO: > -- > 2.52.0 > >