Re: [PATCH v16 08/14] iio: core: add decimal value formatting into 64-bit value

From: Nuno Sá

Date: Mon Jun 08 2026 - 16:34:10 EST

On Thu, 2026-06-04 at 10:59 +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.
>
> Signed-off-by: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>
> ---

Reviewed-by: Nuno Sá <nuno.sa@xxxxxxxxxx>

> drivers/iio/industrialio-core.c | 49 ++++++++++++++++++++++++++++++++---------
> include/linux/iio/types.h       | 20 +++++++++++++++++
> 2 files changed, 59 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index ffe0dc49c4b9..93c2540d4cd2 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -19,6 +19,7 @@
> #include <linux/idr.h>
> #include <linux/kdev_t.h>
> #include <linux/kernel.h>
> +#include <linux/math64.h>
> #include <linux/module.h>
> #include <linux/mutex.h>
> #include <linux/poll.h>
> @@ -26,7 +27,6 @@
> #include <linux/sched.h>
> #include <linux/slab.h>
> #include <linux/wait.h>
> -#include <linux/wordpart.h>
>
> #include <linux/iio/buffer.h>
> #include <linux/iio/buffer_impl.h>
> @@ -656,6 +656,7 @@ static ssize_t __iio_format_value(char *buf, size_t offset,
> unsigned int type,
> int size, const int *vals)
> {
> int tmp0, tmp1;
> + int l = 0;
> s64 tmp2;
> bool scale_db = false;
>
> @@ -699,7 +700,6 @@ static ssize_t __iio_format_value(char *buf, size_t offset,
> unsigned int type,
> case IIO_VAL_INT_MULTIPLE:
> {
> int i;
> - int l = 0;
>
> for (i = 0; i < size; ++i)
> l += sysfs_emit_at(buf, offset + l, "%d ", vals[i]);
> @@ -708,8 +708,25 @@ 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]);
> - return sysfs_emit_at(buf, offset, "%lld", tmp2);
> + return sysfs_emit_at(buf, offset, "%lld",
> +      iio_val_s64_compose(vals[0], vals[1]));
> + case IIO_VAL_DECIMAL64_MILLI:
> + case IIO_VAL_DECIMAL64_MICRO:
> + case IIO_VAL_DECIMAL64_NANO:
> + case IIO_VAL_DECIMAL64_PICO:
> + {
> + int scale = type - IIO_VAL_DECIMAL64_BASE;
> + s64 frac;
> +
> + tmp2 = div64_s64_rem(iio_val_s64_compose(vals[0], vals[1]),
> +      int_pow(10, scale), &frac);
> + if (tmp2 == 0 && frac < 0)
> + l += sysfs_emit_at(buf, offset, "-");
> +
> + l += sysfs_emit_at(buf, offset + l, "%lld.%0*lld", tmp2, scale,
> +    abs(frac));
> + return l;
> + }
> default:
> return 0;
> }
> @@ -979,6 +996,7 @@ static ssize_t iio_write_channel_info(struct device *dev,
> struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> int ret, fract_mult = 100000;
> + int type, dec_scale = 0;
> int integer, fract = 0;
> long long integer64;
> bool is_char = false;
> @@ -989,9 +1007,11 @@ static ssize_t iio_write_channel_info(struct device *dev,
> if (!indio_dev->info->write_raw)
> return -EINVAL;
>
> - if (indio_dev->info->write_raw_get_fmt)
> - switch (indio_dev->info->write_raw_get_fmt(indio_dev,
> - this_attr->c, this_attr->address)) {
> + if (indio_dev->info->write_raw_get_fmt) {
> + type = indio_dev->info->write_raw_get_fmt(indio_dev,
> + this_attr->c,
> + this_attr->address);
> + switch (type) {
> case IIO_VAL_INT:
> fract_mult = 0;
> break;
> @@ -1007,12 +1027,19 @@ static ssize_t iio_write_channel_info(struct device *dev,
> case IIO_VAL_CHAR:
> is_char = true;
> break;
> + case IIO_VAL_DECIMAL64_MILLI:
> + case IIO_VAL_DECIMAL64_MICRO:
> + case IIO_VAL_DECIMAL64_NANO:
> + case IIO_VAL_DECIMAL64_PICO:
> + dec_scale = type - IIO_VAL_DECIMAL64_BASE;
> + fallthrough;
> case IIO_VAL_INT_64:
> is_64bit = true;
> break;
> default:
> return -EINVAL;
> }
> + }
>
> if (is_char) {
> char ch;
> @@ -1021,12 +1048,14 @@ static ssize_t iio_write_channel_info(struct device *dev,
> return -EINVAL;
> integer = ch;
> } else if (is_64bit) {
> - ret = kstrtoll(buf, 0, &integer64);
> + if (dec_scale)
> + ret = kstrtodec64(buf, dec_scale, &integer64);
> + else
> + ret = kstrtoll(buf, 0, &integer64);
> if (ret)
> return ret;
>
> - fract = upper_32_bits(integer64);
> - integer = lower_32_bits(integer64);
> + iio_val_s64_decompose(integer64, &integer, &fract);
> } else {
> ret = __iio_str_to_fixpoint(buf, fract_mult, &integer, &fract,
>     scale_db);
> diff --git a/include/linux/iio/types.h b/include/linux/iio/types.h
> index 4e3099defc1d..924ac9dc6893 100644
> --- a/include/linux/iio/types.h
> +++ b/include/linux/iio/types.h
> @@ -7,6 +7,9 @@
> #ifndef _IIO_TYPES_H_
> #define _IIO_TYPES_H_
>
> +#include <linux/types.h>
> +#include <linux/wordpart.h>
> +
> #include <uapi/linux/iio/types.h>
>
> enum iio_event_info {
> @@ -34,6 +37,23 @@ enum iio_event_info {
> #define IIO_VAL_FRACTIONAL_LOG2 11
> #define IIO_VAL_CHAR 12
>
> +#define IIO_VAL_DECIMAL64_BASE 32
> +#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)
> +
> +static inline s64 iio_val_s64_compose(s32 val0, s32 val1)
> +{
> + return (s64)(((u64)val1 << 32) | (u32)val0);
> +}
> +
> +static inline void iio_val_s64_decompose(s64 dec64, s32 *val0, s32 *val1)
> +{
> + *val0 = lower_32_bits(dec64);
> + *val1 = upper_32_bits(dec64);
> +}
> +
> enum iio_available_type {
> IIO_AVAIL_LIST,
> IIO_AVAIL_RANGE,