Re: [PATCH v4 2/7] iio: adc: hx711: move scale computation to per-device storage

Piyush Patle
2026-04-27T22:39:05Z

On Mon, Apr 27, 2026 at 7:32 PM Andy Shevchenko
<andriy.shevchenko@intel.com> wrote:
>
> On Mon, Apr 27, 2026 at 03:39:33PM +0530, Piyush Patle wrote:
> > The gain-to-scale table hx711_gain_to_scale[] is a global array whose
> > .scale fields are overwritten in hx711_probe() using the AVDD voltage
> > read at probe time. When two HX711 sensors are connected to supplies at
> > different voltages, the second probe call overwrites the scale values
> > computed for the first sensor, silently corrupting its readings.
> >
> > Fix this by removing the .scale field from the global table, making the
> > table const, and adding a per-instance gain_scale[] array to hx711_data.
> > Populate gain_scale[] in hx711_probe() using the device's own AVDD
> > regulator voltage. Update hx711_get_gain_to_scale() and
> > hx711_get_scale_to_gain() to take the per-instance array as a parameter,
> > and update hx711_scale_available_show() to retrieve it via iio_priv().
> >
> > No functional change for single-sensor configurations.
>
> ...
>
> > /*
> > * .scale depends on AVDD which in turn is known as soon as the regulator
> > - * is available
> > - * therefore we set .scale in hx711_probe()
> > + * is available; it is stored per device in hx711_data.gain_scale[]
> > *
> > * channel A in documentation is channel 0 in source code
> > * channel B in documentation is channel 1 in source code
> > */
> > -static struct hx711_gain_to_scale hx711_gain_to_scale[HX711_GAIN_MAX] = {
> > - { 128, 1, 0, 0 },
> > - { 32, 2, 0, 1 },
> > - { 64, 3, 0, 0 }
> > +static const struct hx711_gain_to_scale hx711_gain_to_scale[HX711_GAIN_MAX] = {
> > + { 128, 1, 0 },
> > + { 32, 2, 1 },
> > + { 64, 3, 0 }
>
> I would leave trailing comma, as it is semantically is not the terminator entry.
>
Will add trailing commas to all three initializer lines.

> > };
>
> ...
>
> > {
> > struct iio_dev_attr *iio_attr = to_iio_dev_attr(attr);
> > int channel = iio_attr->address;
> > + struct hx711_data *hx711_data =
> > + iio_priv(dev_to_iio_dev(dev));
>
> First of all, please preserve the reversed xmas tree order.
> Second, it's more than enough room to have it a single line.
Works , will do in v5

>
> struct hx711_data *hx711_data = iio_priv(dev_to_iio_dev(dev));
>
> > int i, len = 0;
>
> --
> With Best Regards,
> Andy Shevchenko
>
>