stuck in "Polling data" until I manually cat "in_..._raw"

[darkdragon-001]

When I run your program (or I even tried to build my own minimalistic program which behaves the same way", then it is stuck in the poll() command. It get's out of it when I manually cat in the sysfs the raw data file in_..._raw. Afterwards the sensor outputs the correct sensor data etc.

It is not a permissions problem (I checked that).

Do you have an idea what else could have caused the problem?

I am using Lenovo ThinkPad Twist S230u with Ubuntu 14.10 (Kernel 3.16).

[svenuniku]

I'm using the same laptop and trying to get sensor data.
My actual setup is Debian Jessie(testing) with a self compiled kernel 3.17.1 ( also tested it with standard kernel of Debian)
Your code worked for me, when I last tried it in April 2014 ( commit 94d130c ). At this time my System was Ubuntu 13.10 with a self compiled kernel 3.14.0 .
I hope you have an idea.

[pfps]

There appears that the sensors get into particular states that are not always handled well by the IIO subsystem. I had these problems in kernels 3.13 and 3.14, but have not had any problems since 3.15. Without access to the actual hardware, it is very hard to determine just what is going wrong.

[darkdragon-001]

Any idea in which direction to look?
Which piece of code or hardware could we debug how?

We are glad about every hint or link we can get. Maybe some resources which helped you while developing your code?
It took me several hours just to understand your code and reproduce what it is doing to understand about the actual modules being used in the process.

[pfps]

It's likely to be some part of the drivers for the hardware.

The most likely culprit, I think, is that the particular hardware may need to be added to the list of hardware that uses the wrong origin for offsets. To check this you need to find out what your sensor chip is, using lsusb -v and then see if it is in the list of quirked devices in the kernel file hid-sensor-hub.c (look for ENUM_QUIRK). The definitions of the symbols are in sensor-id.h

You will be looking for a USB device that is an HID Sensor. Here is what show up on at Yoga 2 Pro - the vendor and product numbers are what are needed.

Bus 002 Device 003: ID 2047:0855 Texas Instruments Invensense Embedded MotionApp HID Sensor
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 8
idVendor 0x2047 Texas Instruments
idProduct 0x0855 Invensense Embedded MotionApp HID Sensor
bcdDevice 11.51
iManufacturer 1 Invensense
iProduct 2 Lenovo Yoga
iSerial 3 44F6806F1F002300
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 41
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 4 Embedded MotionApps
bmAttributes 0xa0
(Bus Powered)
Remote Wakeup
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 3 Human Interface Device
bInterfaceSubClass 0 No Subclass
bInterfaceProtocol 0 None
iInterface 5 HID Sensor Interface
HID Device Descriptor:
bLength 9
bDescriptorType 33
bcdHID 1.01
bCountryCode 0 Not supported
bNumDescriptors 1
bDescriptorType 34 Report
wDescriptorLength 2587
Report Descriptors:
** UNAVAILABLE **
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 20
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 20
Device Status: 0x0000
(Bus Powered)