linux-kernel - Re: [PATCH v3 1/3] iio: Add IIO_DELTA

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Date:   Sat, 5 Aug 2023 19:35:16 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Ramona Bolboaca <ramona.bolboaca@...log.com>
Cc:     <nuno.sa@...log.com>, <linux-iio@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] iio: Add IIO_DELTA_ANGL channel type

On Fri, 4 Aug 2023 09:45:57 +0300
Ramona Bolboaca <ramona.bolboaca@...log.com> wrote:

> The delta angle is defined as a piece-wise integration of angular
> velocity data. The delta angle represents the amount of
> angular displacement between two consecutive measurements and it
> is measured in degrees.

That's not consistent with angl and it should be.
Hence should be radians, with appropriate changes in the scale
exposed by the driver.

> 
> In order to track the total angular displacement during a desired
> period of time, simply sum-up the delta angle samples acquired
> during that time.
> 
> IIO currently does not offer a suitable channel type for this
> type of measurements hence this patch adds it.
> 
> Signed-off-by: Ramona Bolboaca <ramona.bolboaca@...log.com>
> ---
>  Documentation/ABI/testing/sysfs-bus-iio | 14 ++++++++++++++
>  drivers/iio/industrialio-core.c         |  1 +
>  include/uapi/linux/iio/types.h          |  1 +
>  tools/iio/iio_event_monitor.c           |  2 ++
>  4 files changed, 18 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> index a2854dc9a839..1561c33b05a1 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio
> +++ b/Documentation/ABI/testing/sysfs-bus-iio
> @@ -279,6 +279,20 @@ Description:
>  		but should match other such assignments on device).
>  		Units after application of scale and offset are m/s^2.
>  
> +What:		/sys/bus/iio/devices/iio:deviceX/in_deltaangl_x_raw
> +What:		/sys/bus/iio/devices/iio:deviceX/in_deltaangl_y_raw
> +What:		/sys/bus/iio/devices/iio:deviceX/in_deltaangl_z_raw
> +KernelVersion:	6.5
> +Contact:	linux-iio@...r.kernel.org
> +Description:
> +		Angular displacement between two consecutive samples on x, y or
> +		z (may be arbitrarily assigned but should match other such
> +		assignments on device).
> +		In order to compute the total angular displacement during a
> +		desired period of time, the application should sum-up the delta
> +		angle samples acquired during that time.
> +		Units after application of scale and offset are angles.

Units above are degrees, but should be radians.

> +
>  What:		/sys/bus/iio/devices/iio:deviceX/in_angl_raw
>  What:		/sys/bus/iio/devices/iio:deviceX/in_anglY_raw
>  KernelVersion:	4.17
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index a92b8b6ad647..2e2fd0be2504 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -89,6 +89,7 @@ static const char * const iio_chan_type_name_spec[] = {
>  	[IIO_POSITIONRELATIVE]  = "positionrelative",
>  	[IIO_PHASE] = "phase",
>  	[IIO_MASSCONCENTRATION] = "massconcentration",
> +	[IIO_DELTA_ANGL] = "deltaangl",
>  };
>  
>  static const char * const iio_modifier_names[] = {
> diff --git a/include/uapi/linux/iio/types.h b/include/uapi/linux/iio/types.h
> index c79f2f046a0b..55666a17d311 100644
> --- a/include/uapi/linux/iio/types.h
> +++ b/include/uapi/linux/iio/types.h
> @@ -47,6 +47,7 @@ enum iio_chan_type {
>  	IIO_POSITIONRELATIVE,
>  	IIO_PHASE,
>  	IIO_MASSCONCENTRATION,
> +	IIO_DELTA_ANGL,
>  };
>  
>  enum iio_modifier {
> diff --git a/tools/iio/iio_event_monitor.c b/tools/iio/iio_event_monitor.c
> index 0a5c2bb60030..3505450060e6 100644
> --- a/tools/iio/iio_event_monitor.c
> +++ b/tools/iio/iio_event_monitor.c
> @@ -59,6 +59,7 @@ static const char * const iio_chan_type_name_spec[] = {
>  	[IIO_POSITIONRELATIVE] = "positionrelative",
>  	[IIO_PHASE] = "phase",
>  	[IIO_MASSCONCENTRATION] = "massconcentration",
> +	[IIO_DELTA_ANGL] = "deltaangl",
>  };
>  
>  static const char * const iio_ev_type_text[] = {
> @@ -173,6 +174,7 @@ static bool event_is_known(struct iio_event_data *event)
>  	case IIO_POSITIONRELATIVE:
>  	case IIO_PHASE:
>  	case IIO_MASSCONCENTRATION:
> +	case IIO_DELTA_ANGL:
>  		break;
>  	default:
>  		return false;