Re: [PATCH v10 05/11] iio: core: add decimal value formatting into 64-bit value

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 4 May 2026 11:42:38 +0100
Rodrigo Alencar <455.rodrigo.alencar@gmail.com> wrote:

> On 26/04/15 10:51AM, Rodrigo Alencar wrote:
> > 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. Helper macros 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.
> > 
> > Signed-off-by: Rodrigo Alencar <rodrigo.alencar@analog.com>  
> 
> ...
> 
> > --- a/include/linux/iio/types.h
> > +++ b/include/linux/iio/types.h
> > @@ -7,6 +7,7 @@
> >  #ifndef _IIO_TYPES_H_
> >  #define _IIO_TYPES_H_
> >  
> > +#include <linux/wordpart.h>
> >  #include <uapi/linux/iio/types.h>
> >  
> >  enum iio_event_info {
> > @@ -34,6 +35,38 @@ enum iio_event_info {
> >  #define IIO_VAL_FRACTIONAL_LOG2 11
> >  #define IIO_VAL_CHAR 12
> >  
> > +#define IIO_VAL_DECIMAL64_BASE		100
> > +#define IIO_VAL_DECIMAL64_MILLI		(IIO_VAL_DECIMAL64_BASE + 3)
> > +#define IIO_VAL_DECIMAL64_MICRO		(IIO_VAL_DECIMAL64_BASE + 6)
> > +#define IIO_VAL_DECIMAL64_NANO		(IIO_VAL_DECIMAL64_BASE + 9)
> > +#define IIO_VAL_DECIMAL64_PICO		(IIO_VAL_DECIMAL64_BASE + 12)
> > +
> > +#define iio_val_s64_compose(_val0, _val1)				\
> > +	({ (s64)((((u64)(_val1)) << 32) | (u32)(_val0)); })
> > +
> > +#define iio_val_s64_from_array(_vals)					\
> > +	({								\
> > +		const int *_arr = (const int *)(_vals);			\
> > +		s64 _dec64 = iio_val_s64_compose(_arr[0], _arr[1]);	\
> > +									\
> > +		_dec64;							\
> > +	})
> > +
> > +#define iio_val_s64_decompose(_dec64, _val0, _val1)			\
> > +	do {								\
> > +		s64 _tmp64 = (s64)(_dec64);				\
> > +									\
> > +		*(_val0) = lower_32_bits(_tmp64);			\
> > +		*(_val1) = upper_32_bits(_tmp64);			\
> > +	} while (0)
> > +
> > +#define iio_val_s64_array_populate(_dec64, _vals)			\
> > +	do {								\
> > +		int *_arr = (int *)(_vals);				\
> > +									\
> > +		iio_val_s64_decompose((_dec64), &_arr[0], &_arr[1]);	\
> > +	} while (0)  
> 
> Hi Jonathan,
> 
> Are those macros ok? in terms of where they are declared or whether they
> should be static inline functions? any preferences?

My preference would be for static inline functions rather than macros given
all the types are known here.

> 
> > +
> >  enum iio_available_type {
> >  	IIO_AVAIL_LIST,
> >  	IIO_AVAIL_RANGE,
> > 
> > -- 
> > 2.43.0
> >   
>