linux-kernel - Re: [PATCH v2 3/3] iio: imu: adis16475.c: Add delta angle and delta velocity channels

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Message-ID: <20230729154726.49b9a86b@jic23-huawei>
Date:   Sat, 29 Jul 2023 15:47:26 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     "Bolboaca, Ramona" <Ramona.Bolboaca@...log.com>
Cc:     "Sa, Nuno" <Nuno.Sa@...log.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] iio: imu: adis16475.c: Add delta angle and delta
 velocity channels

On Wed, 26 Jul 2023 10:23:02 +0000
"Bolboaca, Ramona" <Ramona.Bolboaca@...log.com> wrote:

> > On Wed, 19 Jul 2023 15:31:52 +0300
> > Ramona Bolboaca <ramona.bolboaca@...log.com> wrote:
> >   
> > > Add support for delta angle and delta velocity raw and buffer
> > > readings to adis16475 driver.
> > >
> > > Signed-off-by: Ramona Bolboaca <ramona.bolboaca@...log.com>  
> > As noted in my reply to Nuno's review, the question of channel type
> > is still unresolved.
> >   
> 
> Hi Jonathan,
> 
> I think Nuno already offered the definition from the data-sheet, but let me
> mention it here again for context:
> 
> Delta angle:
> In addition to the angular rate of rotation (gyroscope) measurements around
> each axis (x, y, and z), the ADIS16505 also provides delta angle measurements
> that represent a calculation of angular displacement between each sample update.
> 
> Delta velocity:
> In addition to the linear acceleration measurements along each axis (x, y, and
> z), the ADIS16505 also provides delta velocity measurements that represent a
> calculation of linear velocity change between each sample update.
> 
> Seeing how we cannot find something more suitable, do you think it would make
> sense to add these new channels to IIO: something like IIO_DELTA_VELOCITY and
> IIO_DELTA_ANGLE and specify in ABI docs that these measurements are relative
> to the previous sample? Or do you have something else in mind?

Yes - I think we need these new channel types to avoid inconsistent use of the
existing types.  In the documentation I would give a little context, particularly
around the common use of these being to simply sum them over time.

Jonathan


> 
> Thank you,
> Ramona Bolboaca
> 
> > https://urldefense.com/v3/__https://lore.kernel.org/all/20230720193457.27
> > 2f02a9@...23-
> > huawei/__;!!A3Ni8CS0y2Y!52Dhq_Yj9srV_lE8JgPysp2b3Lbg9U2w94VIGTMa8
> > 3hepJgv-NCnFWomV83Ud5C3TGp3tMMI0IDVRYZV5N8$
> > 
> > Thanks,
> > 
> > Jonathan