Re: possible odd acceleration scaling

From: Jonathan Cameron <jic23@kernel.org>
To: rrs@researchut.com, linux-iio@vger.kernel.org,
	Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
	Bastien Nocera <hadess@hadess.net>
Subject: Re: possible odd acceleration scaling
Date: Tue, 13 Sep 2016 19:01:31 +0100	[thread overview]
Message-ID: <d275ff67-4335-a6f4-b60b-c4227a59b34c@kernel.org> (raw)
In-Reply-To: <a9078c9f-0d07-35bc-e449-2cfeee7b7987@kernel.org>

On 13/09/16 18:50, Jonathan Cameron wrote:
> On 13/09/16 18:30, Ritesh Raj Sarraf wrote:
>> Hello Srinivas and Others,
>>
>> [Please CC me in replies. I'm not subscribed to the list]
>>
>> This email is in regard to an odd behavior, we seems to have discovered with
>> iio-sensor-proxy version 1.2 and the iio driver in Linux, maybe particular to
>> the following driver.
>>
>>
>> rrs@learner:~$ lsusb 
>> Bus 003 Device 002: ID 8087:8000 Intel Corp. 
>> Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
>> Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
>> Bus 001 Device 006: ID 048d:8350 Integrated Technology Express, Inc. 
>> Bus 001 Device 005: ID 0bda:b728 Realtek Semiconductor Corp. 
>> Bus 001 Device 004: ID 04f2:b40f Chicony Electronics Co., Ltd 
>> Bus 001 Device 003: ID 04f3:0303 Elan Microelectronics Corp. 
>> Bus 001 Device 002: ID 0bda:0129 Realtek Semiconductor Corp. RTS5129 Card Reader
>> Controller
>> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
>> 2016-09-13 / 22:56:58 ♒♒♒  ☺  
>>
>>
>> rrs@learner:/sys/devices/pci0000:00/0000:00:14.0/usb1/1-8/1-
>> 8:1.0/0003:048D:8350.0002/HID-SENSOR-200073.4.auto$ find iio\:device2/ -iname
>> "*scale*" -print -exec cat '{}' \;
>> iio:device2/in_accel_scale
>> 0.009806
> Looking at your bug report, raw readings are around magnitude 1000.
> 1000*0.009806 = 9.81
> 
> Given accelerations in IIO are in m/s^2 I'm slightly confused...
> 
> Guessing the iio-sensor-proxy might be getting it's idea of what counts
> as orientation from the wrong place?  
> 
> I couldn't immediately see where it figures that out...
Ah, found it. In orientation.c (obvious I guess)

Too late in the day here for me to spot exactly why the rounding
errors being introduced are resulting in this concluding that
the orientation isn't changing significantly.

Perhaps stick a line in the sensor proxy to spit out the
computed 'rotation' value?

Thanks,

Jonathan
> 
> Jonathan
> 
>> 2016-09-13 / 22:37:29 ♒♒♒  ☺  
>>
>>
>> Machine: Lenovo Yoga 2 13.
>>
>>
>> For a background, please have a look at the github bug report.
>> https://github.com/hadess/iio-sensor-proxy/issues/100
>>
>>
>> If you need any information, please let me know. I'm not sure what other
>> information to provide upfront, that maybe be relevant.
>>
>>
>>
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