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From:   Jean-Baptiste Maneyrol <JManeyrol@invensense.com>
To:     Lars-Peter Clausen <lars@metafoo.de>,
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Subject: Re: [PATCH v3 06/13] iio: imu: inv_icm42600: add temperature sensor
 support
Thread-Topic: [PATCH v3 06/13] iio: imu: inv_icm42600: add temperature sensor
 support
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Date:   Sun, 14 Jun 2020 20:35:13 +0000
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Hello Lars,=0A=
=0A=
for the temperature data, the problem is that temperature in the FIFO (used=
 in buffer) is not in the same format than when reading the register.=0A=
=0A=
Reading the temperature register return a full precision value on 16 bits. =
I am using a PROCESSED attribute for it.=0A=
Temperature data in buffer (coming from the FIFO) is on 8 bits in lower pre=
cision. It is reported as raw data, thus the need of the offset and scale v=
alues.=0A=
=0A=
So offset and scale values are only for transforming the temperature data f=
rom the buffer, and direct read is a full precision already processed in m=
=B0C.=0A=
=0A=
Thanks for the review,=0A=
JB=0A=
=0A=
From: Lars-Peter Clausen <lars@metafoo.de>=0A=
Sent: Sunday, June 14, 2020 17:10=0A=
To: Jean-Baptiste Maneyrol <JManeyrol@invensense.com>; jic23@kernel.org <ji=
c23@kernel.org>; robh+dt@kernel.org <robh+dt@kernel.org>; robh@kernel.org <=
robh@kernel.org>; mchehab+huawei@kernel.org <mchehab+huawei@kernel.org>; da=
vem@davemloft.net <davem@davemloft.net>; gregkh@linuxfoundation.org <gregkh=
@linuxfoundation.org>=0A=
Cc: linux-iio@vger.kernel.org <linux-iio@vger.kernel.org>; devicetree@vger.=
kernel.org <devicetree@vger.kernel.org>; linux-kernel@vger.kernel.org <linu=
x-kernel@vger.kernel.org>=0A=
Subject: Re: [PATCH v3 06/13] iio: imu: inv_icm42600: add temperature senso=
r support =0A=
=A0=0A=
=A0CAUTION: This email originated from outside of the organization. Please =
make sure the sender is who they say they are and do not click links or ope=
n attachments unless you recognize the sender and know the content is safe.=
=0A=
=0A=
On 6/8/20 10:42 PM, Jean-Baptiste Maneyrol wrote:=0A=
> +=A0=A0=A0=A0 case IIO_CHAN_INFO_PROCESSED:=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 ret =3D iio_device_claim_direct_mod=
e(indio_dev);=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (ret)=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 return ret;=
=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 ret =3D inv_icm42600_temp_read(st, =
&temp);=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 iio_device_release_direct_mode(indi=
o_dev);=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (ret)=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 return ret;=
=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 *val =3D temp;=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 return IIO_VAL_INT;=0A=
> +=A0=A0=A0=A0 case IIO_CHAN_INFO_SCALE:=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 *val =3D 483;=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 *val2 =3D 91787;=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 return IIO_VAL_INT_PLUS_MICRO;=0A=
> +=A0=A0=A0=A0 case IIO_CHAN_INFO_OFFSET:=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 *val =3D 25000;=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 return IIO_VAL_INT;=0A=
=0A=
If the data is returned processed there is no need to specify scale and =0A=
offset.=0A=
=0A=
But since the transformation to turn the data into standard units is a =0A=
simple linear transform the preferred way to handle this is to return =0A=
RAW data and specify scale and offset.=0A=