Re: [PATCH v8 2/6] iio: Replace 'sign' field with union in struct iio_scan_type

[David Lechner]

On 3/17/26 10:04 AM, Francesco Lavra wrote:
> This field is used to differentiate between signed and unsigned integers.
> A following commit will extend its use in order to add support for non-
> integer scan elements; therefore, replace it with a union that contains a
> more generic 'format' field. This union will be dropped when all drivers
> are changed to use the format field.
> Opportunistically replace character literals with symbolic constants that
> represent the set of allowed values for the format field.
> 
> Signed-off-by: Francesco Lavra <flavra@xxxxxxxxxxxx>
> ---
>  Documentation/driver-api/iio/buffers.rst |  4 ++--
>  include/linux/iio/iio.h                  | 17 +++++++++++++++--
>  2 files changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/driver-api/iio/buffers.rst b/Documentation/driver-api/iio/buffers.rst
> index 63f364e862d1..e16abaf826fe 100644
> --- a/Documentation/driver-api/iio/buffers.rst
> +++ b/Documentation/driver-api/iio/buffers.rst
> @@ -78,7 +78,7 @@ fields in iio_chan_spec definition::
>     /* other members */
>             int scan_index
>             struct {
> -                   char sign;
> +                   char format;
>                     u8 realbits;
>                     u8 storagebits;
>                     u8 shift;
> @@ -98,7 +98,7 @@ following channel definition::
>  		   /* other stuff here */
>  		   .scan_index = 0,
>  		   .scan_type = {
> -		           .sign = 's',
> +		           .format = IIO_SCAN_FORMAT_SIGNED_INT,
>  			   .realbits = 12,
>  			   .storagebits = 16,
>  			   .shift = 4,
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index a9ecff191bd9..d48a0ab01b8d 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -176,9 +176,19 @@ struct iio_event_spec {
>  	unsigned long mask_shared_by_all;
>  };
>  
> +/*
> + * Format values in scan type
> + * @IIO_SCAN_FORMAT_SIGNED_INT: Signed integer (two's complement).
> + * @IIO_SCAN_FORMAT_UNSIGNED_INT: Unsigned integer.
> + */

We could make this proper kernel doc format with one comment per macro.

> +#define IIO_SCAN_FORMAT_SIGNED_INT	's'
> +#define IIO_SCAN_FORMAT_UNSIGNED_INT	'u'
> +
>  /**
>   * struct iio_scan_type - specification for channel data format in buffer
> - * @sign:		's' or 'u' to specify signed or unsigned
> + * @sign:		Deprecated, use @format instead.
> + * @format:		Data format, can have any of the IIO_SCAN_FORMAT_*
> + *			values.
>   * @realbits:		Number of valid bits of data
>   * @storagebits:	Realbits + padding
>   * @shift:		Shift right by this before masking out realbits.
> @@ -189,7 +199,10 @@ struct iio_event_spec {
>   * @endianness:		little or big endian
>   */
>  struct iio_scan_type {
> -	char	sign;
> +	union {
> +		char sign;
> +		char format;
> +	};
>  	u8	realbits;
>  	u8	storagebits;
>  	u8	shift;