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[PATCH v7 2/6] iio: Replace 'sign' field with union in struct iio_scan_type

Francesco Lavra posted 6 patches 1 month, 1 week ago
There is a newer version of this series
[PATCH v7 2/6] iio: Replace 'sign' field with union in struct iio_scan_type
Posted by Francesco Lavra 1 month, 1 week ago 
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.

Signed-off-by: Francesco Lavra <flavra@baylibre.com>
---
 Documentation/driver-api/iio/buffers.rst | 4 ++--
 include/linux/iio/iio.h                  | 7 +++++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/Documentation/driver-api/iio/buffers.rst b/Documentation/driver-api/iio/buffers.rst
index 63f364e862d1..f36e6d00173f 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 = 's',
 			   .realbits = 12,
 			   .storagebits = 16,
 			   .shift = 4,
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index a9ecff191bd9..61f1dfc14e02 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -178,7 +178,7 @@ struct iio_event_spec {
 
 /**
  * struct iio_scan_type - specification for channel data format in buffer
- * @sign:		's' or 'u' to specify signed or unsigned
+ * @format:		(signed or unsigned) integer, or floating point
  * @realbits:		Number of valid bits of data
  * @storagebits:	Realbits + padding
  * @shift:		Shift right by this before masking out realbits.
@@ -189,7 +189,10 @@ 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;
-- 
2.39.5
Re: [PATCH v7 2/6] iio: Replace 'sign' field with union in struct iio_scan_type
Posted by Jonathan Cameron 1 month, 1 week ago 
On Wed,  4 Mar 2026 09:06:40 +0100
Francesco Lavra <flavra@baylibre.com> 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.
> 
> Signed-off-by: Francesco Lavra <flavra@baylibre.com>
> ---
>  Documentation/driver-api/iio/buffers.rst | 4 ++--
>  include/linux/iio/iio.h                  | 7 +++++--
>  2 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/driver-api/iio/buffers.rst b/Documentation/driver-api/iio/buffers.rst
> index 63f364e862d1..f36e6d00173f 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 = 's',
This made me wonder if we should use this opportunity to restrict
the flexibility of what can go in .format via some defines?

#define IIO_SCAN_FORMAT_SIGNED_INT 's'
#define IIO_SCAN_FORMAT_UNSIGNED_INT 'u'
#define IIO_SCAN_FORMAT_FLOAT 'f'

or something like that.  Given the aim is to convert all current
instances we can move to the macros as part of switching from
sign to format.


>  			   .realbits = 12,
>  			   .storagebits = 16,
>  			   .shift = 4,
Re: [PATCH v7 2/6] iio: Replace 'sign' field with union in struct iio_scan_type
Posted by David Lechner 1 month, 1 week ago 
On 3/4/26 2:06 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.
> 
> Signed-off-by: Francesco Lavra <flavra@baylibre.com>
> ---
>  Documentation/driver-api/iio/buffers.rst | 4 ++--
>  include/linux/iio/iio.h                  | 7 +++++--
>  2 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/driver-api/iio/buffers.rst b/Documentation/driver-api/iio/buffers.rst
> index 63f364e862d1..f36e6d00173f 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 = 's',
>  			   .realbits = 12,
>  			   .storagebits = 16,
>  			   .shift = 4,
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index a9ecff191bd9..61f1dfc14e02 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -178,7 +178,7 @@ struct iio_event_spec {
>  
>  /**
>   * struct iio_scan_type - specification for channel data format in buffer
> - * @sign:		's' or 'u' to specify signed or unsigned
> + * @format:		(signed or unsigned) integer, or floating point

We should keep the list of valid values here.

>   * @realbits:		Number of valid bits of data
>   * @storagebits:	Realbits + padding
>   * @shift:		Shift right by this before masking out realbits.
> @@ -189,7 +189,10 @@ struct iio_event_spec {
>   * @endianness:		little or big endian
>   */
>  struct iio_scan_type {
> -	char	sign;
> +	union {
> +		char sign;
> +		char format;

Could add some comments here to say that format should be used
in new code and sign will be removed eventually.

> +	};
>  	u8	realbits;
>  	u8	storagebits;
>  	u8	shift;
Re: [PATCH v7 2/6] iio: Replace 'sign' field with union in struct iio_scan_type
Posted by Jonathan Cameron 1 month, 1 week ago 
On Wed, 4 Mar 2026 16:55:42 -0600
David Lechner <dlechner@baylibre.com> wrote:

> On 3/4/26 2:06 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.
> > 
> > Signed-off-by: Francesco Lavra <flavra@baylibre.com>
> > ---
> >  Documentation/driver-api/iio/buffers.rst | 4 ++--
> >  include/linux/iio/iio.h                  | 7 +++++--
> >  2 files changed, 7 insertions(+), 4 deletions(-)
> > 
> > diff --git a/Documentation/driver-api/iio/buffers.rst b/Documentation/driver-api/iio/buffers.rst
> > index 63f364e862d1..f36e6d00173f 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 = 's',
> >  			   .realbits = 12,
> >  			   .storagebits = 16,
> >  			   .shift = 4,
> > diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> > index a9ecff191bd9..61f1dfc14e02 100644
> > --- a/include/linux/iio/iio.h
> > +++ b/include/linux/iio/iio.h
> > @@ -178,7 +178,7 @@ struct iio_event_spec {
> >  
> >  /**
> >   * struct iio_scan_type - specification for channel data format in buffer
> > - * @sign:		's' or 'u' to specify signed or unsigned

I think this is going to trigger kernel-doc warnings.  So I'd keep the docs
but mention it's deprecated in favour of format.

> > + * @format:		(signed or unsigned) integer, or floating point  
> 
> We should keep the list of valid values here.
> 
> >   * @realbits:		Number of valid bits of data
> >   * @storagebits:	Realbits + padding
> >   * @shift:		Shift right by this before masking out realbits.
> > @@ -189,7 +189,10 @@ struct iio_event_spec {
> >   * @endianness:		little or big endian
> >   */
> >  struct iio_scan_type {
> > -	char	sign;
> > +	union {
> > +		char sign;
> > +		char format;  
> 
> Could add some comments here to say that format should be used
> in new code and sign will be removed eventually.
> 
> > +	};
> >  	u8	realbits;
> >  	u8	storagebits;
> >  	u8	shift;  
>

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