Channel data values for IIO based st_sensors (st_accel, st_pressure) are incorrect

[Shrirang Bagul]

Multi-channel reads from IIO based st_sensors (st_pressure and st_accel) drivers fail to report correct results through the devfs (/dev/iio:deviceX) interface.

Dell IoT gateways have sensors which uses IIO kernel drivers to read values from STM accelerometer (lng2dm) and pressure sensor (lps22hb). Pressure, temperature and acceleration channel values are incorrect and not in agreement with the values reported from sysfs with the present drivers in Ubuntu Xenial kernel.

This bug is used for tracking purposes, please do not triage.

[Shrirang Bagul (shrirang-bagul)]

More details:

st_pressure: lps22hb:
=====================
Temperature reading on pressure sensor LPS22HB is not correct from IIO sysfs or devfs
Reading from I2C: 37.64 °C

Reading from IIO sysfs: 0 °C
in_temp_raw: 0
in_temp_scale: 10

Reading from IIO devfs: -307200.0 °C
"0088" is the raw output for temperature got from following output:
root@caracalla:~# cat /dev/iio\:device3 | xxd -
00000000: ee14 3e66 0088 3614 3e66 0088 7914 3e66 ..>f..6.>f..y.>f
00000010: 0088 ff14 3e66 0088 ff14 3e66 0088 8214 ....>f....>f....

st_accel: lng2dm:
=================
Reading of accelerometer LNG2DM is not correct from IIO devfs

From I2C:
Reading of accel_x channel from I2C: 0.15298374 m/(s^2)
Reading of accel_y channel from I2C: 9.9439431 m/(s^2)
Reading of accel_z channel from I2C: 0.91790244 m/(s^2)

From IIO sysfs(Got by (raw + offset)*scale ):
Reading of accel_x channel from IIO sysfs: 0.152983 m/(s^2)
Reading of accel_y channel from IIO sysfs: 9.943895000000001 m/(s^2)
Reading of accel_z channel from IIO sysfs: 0.9178980000000001 m/(s^2)

From IIO devfs:
Reading of accel_x channel from IIO devfs: 0.152983 m/(s^2)
Reading of accel_y channel from IIO devfs: 0.0 m/(s^2)
Reading of accel_z channel from IIO devfs: 9.943895000000001 m/(s^2)

Have checked channel index: 0 for x, 1 for y, 2 for z

So "01" for x, "00" for y, "41" for z are the raw output got from following output:
root@caracalla:/# cat /dev/iio\:device2 | xxd -
00000000: 0100 4101 0041 0100 4101 0041 0000 4101 ..A..A..A..A..A.

[Kleber Sacilotto de Souza (kleber-souza)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-xenial' to 'verification-done-xenial'. If the problem still exists, change the tag 'verification-needed-xenial' to 'verification-failed-xenial'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 4.4.0-75.96

---------------
linux (4.4.0-75.96) xenial; urgency=low

  * linux: 4.4.0-75.96 -proposed tracker (LP: #1684441)

  * [Hyper-V] hv: util: move waiting for release to hv_utils_transport itself
    (LP: #1682561)
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linux (4.4.0-74.95) xenial; urgency=low

  * linux: 4.4.0-74.95 -proposed tracker (LP: #1682041)

  * [Hyper-V] hv: vmbus: Raise retry/wait limits in vmbus_post_msg()
    (LP: #1681893)
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linux (4.4.0-73.94) xenial; urgency=low

  * linux: 4.4.0-73.94 -proposed tracker (LP: #1680416)

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