Re: [PATCH v15 06/12] iio: core: add decimal value formatting into 64-bit value

[Rodrigo Alencar]

On 26/06/02 05:56PM, Nuno Sá wrote:
> On Mon, 2026-06-01 at 16:12 +0100, Rodrigo Alencar wrote:
> > On 26/06/01 10:43AM, Nuno Sá wrote:
> > > On Sun, May 31, 2026 at 09:30:49AM +0100, Rodrigo Alencar via B4 Relay wrote:
> > > > From: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>
> > > > 
> > > > Create new format types for iio values (IIO_VAL_DECIMAL64_*), which
> > > > defines the representation of fixed decimal point values into a single
> > > > 64-bit number. This new format increases the range of represented values,
> > > > allowing for integer parts greater than 2^32, as bits are not "wasted"
> > > > in the fractional part, which can be seen in IIO_VAL_INT_PLUS_MICRO and
> > > > IIO_VAL_INT_PLUS_NANO. Helpers are created to compose and decompose 64-bit
> > > > decimals into integer values used in IIO formatting interfaces, which
> > > > creates consistency and avoid error-prone manual assignments when using
> > > > wordpart macros. When doing the parsing, kstrtodec64() is used with the
> > > > scale defined by the specific decimal format type.

...

> > > > @@ -707,8 +707,25 @@ static ssize_t __iio_format_value(char *buf, size_t
> > > > offset, unsigned int type,
> > > >  	case IIO_VAL_CHAR:
> > > >  		return sysfs_emit_at(buf, offset, "%c", (char)vals[0]);
> > > >  	case IIO_VAL_INT_64:
> > > > -		tmp2 = (s64)((((u64)vals[1]) << 32) | (u32)vals[0]);
> > > > +		tmp2 = iio_val_s64_from_s32s(vals);
> > > 
> > > I might be missing something but can't we just call
> > > iio_val_s64_compose()? Likely even inline in sysfs_emit_at()?
> > 
> > There is a compose() already.
> > 
> 
> Yes and I was suggesting using that one instead iio_val_s64_from_s32s() :). To be
> consistent to what you use in the other path (which is decompose() if I'm not
> mistaken).
> 
> >  
> > > It would match your call to iio_val_s64_decompose() below.
> > 
> > here are the helpers prototype:
> > 
> > 	s64 iio_val_s64_compose(s32 val0, s32 val1);
> > 	s64 iio_val_s64_from_s32s(const s32 *vals);
> > 
> > 	void iio_val_s64_decompose(s64 dec64, s32 *val0, s32 *val1);
> > 	void iio_val_s64_to_s32s(s64 dec64, s32 *vals);
> >  
> 
> Yes and it feels that iio_val_s64_compose() and iio_val_s64_decompose() are the only
> ones we really need? (Maybe with other naming if you prefer iio_val_s64_from_s32s()
> and iio_val_s64_to_s32s()).
> 
> > > And the above makes me wonder if the compose()/decompose() are not the
> > > only helpers we need? At least in terms of parameters? I mean, just
> > > assuming we only have two integers instead of allowing s32* and opening
> > > the door for misbehave :)?
> > 
> > I suppose we would really need some sort of:
> > 
> > union iio_val {
> > 	s32 val32[2];
> > 	s64 val64;
> > };
> > 
> > or even add a:
> > 
> > 	struct { void *ptr, size_t size }
> 
> I just meant using two where we just have (s32 val1, s32 vals2) given that is
> what IIO has anyways. No need to overthinking it for now IMO.

Understood. will drop iio_val_s64_from_s32s() and iio_val_s64_to_s32s()!

-- 
Kind regards,

Rodrigo Alencar