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From:   Jean-Baptiste Maneyrol <JManeyrol@invensense.com>
To:     Jonathan Cameron <jic23@kernel.org>
CC:     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
Thread-Index: AQHWPdWIUjAhv0WNM0u1pU/hnDKuy6jYQFCAgABZXLeACSG0gIACtcSW
Date:   Mon, 22 Jun 2020 09:21:25 +0000
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Hi Jonathan,=0A=
=0A=
no problem, I can rework temperature to have the same raw output for both c=
ases (with just decreased resolution for the FIFO case).=0A=
=0A=
v4 series is coming soon with the fix.=0A=
=0A=
Thanks,=0A=
JB=0A=
=0A=
From: Jonathan Cameron <jic23@kernel.org>=0A=
Sent: Saturday, June 20, 2020 17:57=0A=
To: Jean-Baptiste Maneyrol <JManeyrol@invensense.com>=0A=
Cc: Lars-Peter Clausen <lars@metafoo.de>; robh+dt@kernel.org <robh+dt@kerne=
l.org>; robh@kernel.org <robh@kernel.org>; mchehab+huawei@kernel.org <mcheh=
ab+huawei@kernel.org>; davem@davemloft.net <davem@davemloft.net>; gregkh@li=
nuxfoundation.org <gregkh@linuxfoundation.org>; linux-iio@vger.kernel.org <=
linux-iio@vger.kernel.org>; devicetree@vger.kernel.org <devicetree@vger.ker=
nel.org>; linux-kernel@vger.kernel.org <linux-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 Sun, 14 Jun 2020 20:35:13 +0000=0A=
Jean-Baptiste Maneyrol <JManeyrol@invensense.com> wrote:=0A=
=0A=
> Hello Lars,=0A=
> =0A=
> for the temperature data, the problem is that temperature in the FIFO (us=
ed 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 p=
recision. It is reported as raw data, thus the need of the offset and scale=
 values.=0A=
> =0A=
> So offset and scale values are only for transforming the temperature data=
 from the buffer, and direct read is a full precision already processed in =
m=B0C.=0A=
=0A=
That is a problem.=A0 We have no means of describing it in IIO.=0A=
=0A=
If the channel is processed via sysfs the assumption would normally=0A=
be that it is processed in the buffer as well. We don't really=0A=
have any means of describing the two separately.=0A=
=0A=
In cases where we've seen this before the way around it was to=0A=
change the data in the fifo so that the scaling was the same as the=0A=
sysfs channel (usually it's just a bit of padding).=0A=
=0A=
Can we do that here?=A0 Looks like the ratio is 1:64 so should=0A=
be possible. =0A=
=0A=
=0A=
=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 <=
jic23@kernel.org>; robh+dt@kernel.org <robh+dt@kernel.org>; robh@kernel.org=
 <robh@kernel.org>; mchehab+huawei@kernel.org <mchehab+huawei@kernel.org>; =
davem@davemloft.net <davem@davemloft.net>; gregkh@linuxfoundation.org <greg=
kh@linuxfoundation.org>=0A=
> Cc: linux-iio@vger.kernel.org <linux-iio@vger.kernel.org>; devicetree@vge=
r.kernel.org <devicetree@vger.kernel.org>; linux-kernel@vger.kernel.org <li=
nux-kernel@vger.kernel.org>=0A=
> Subject: Re: [PATCH v3 06/13] iio: imu: inv_icm42600: add temperature sen=
sor support =0A=
> =A0=0A=
> =A0CAUTION: This email originated from outside of the organization. Pleas=
e make sure the sender is who they say they are and do not click links or o=
pen attachments unless you recognize the sender and know the content is saf=
e.=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_m=
ode(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 re=
t;=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(in=
dio_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 re=
t;=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;=A0 =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=