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

[David Lechner]

On 3/23/26 11:04 AM, Francesco Lavra wrote:
> On Sat, 2026-03-21 at 12:22 -0500, David Lechner wrote:
>> 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.
> 
> Actually, a set of related #defines can be documented with a single
> comment. I see a few examples doing that in include/linux/gfp_types.h and
> include/linux/fpga/fpga-mgr.h

Fancy. Although, IDEs tend to be able to handle doc comments better
if they are not combined (i.e. getting the docs when you hold the
mouse over an identifier).

> 
> 
>>> +#define IIO_SCAN_FORMAT_SIGNED_INT     's'
>>> +#define IIO_SCAN_FORMAT_UNSIGNED_INT   'u'
>>> +
>