Re: [PATCH v5 3/3] iio: dac: mcp4821: add configurable gain support

[Nikhil Gautam <nikhilgtr@gmail.com>]

On Tue, Apr 14, 2026 at 08:57:35AM -0500, David Lechner wrote:
> On 4/14/26 4:22 AM, Nikhil Gautam wrote:
> 
> > +	*val = div_s64_rem(tmp, 1000000LL, &micro);
> > +	*val2 = micro;
> 
> Technically, IIO_VAL_FRACTIONAL_LOG2 can print up to 9 digits after
> the decimal, so this would be safer to do nano instead of micro.
> 
> For that, we need to also implement a write_raw_get_fmt() callback.
>

Thanks for the suggestion.

Currently the driver uses IIO_VAL_FRACTIONAL_LOG2 for the scale
attribute this format is sufficient for all supported chips
(8, 10 and 12-bit), the resulting scale values
are exact and can be represented without loss of precision.

The write path validates the scale values based on exact matches of the
expected values, so additional precision (e.g. nano) is not required.

Using INT_PLUS_NANO would also require changing the existing format and
implementing write_raw_get_fmt(), which does not seem necessary here.

So keeping IIO_VAL_FRACTIONAL_LOG2 for both read and write paths.