linux-kernel - Re: iio/hid-sensor-accel-3d: no output from /dev/iio:device*?

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Message-ID: <CAOhV88MxvEEPB9=8QjiQWbXuCX6FEkA4p=To89Cpcz-M0WOC7A@mail.gmail.com>
Date:	Thu, 17 Dec 2015 17:59:47 -0800
From:	Nish Aravamudan <nish.aravamudan@...il.com>
To:	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:	Jiri Kosina <jikos@...nel.org>,
	Jonathan Cameron <jic23@...nel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald <pmeerw@...erw.net>,
	linux-input@...r.kernel.org, linux-iio@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Crt Mori <cmo@...exis.com>
Subject: Re: iio/hid-sensor-accel-3d: no output from /dev/iio:device*?

On Thu, Dec 17, 2015 at 5:16 PM, Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
> On Thu, 2015-12-17 at 17:07 -0800, Nish Aravamudan wrote:
>> On Thu, Dec 17, 2015 at 4:51 PM, Srinivas Pandruvada
>> <srinivas.pandruvada@...ux.intel.com> wrote:
>> > On Thu, 2015-12-17 at 15:38 -0800, Nish Aravamudan wrote:
>> > > [Starting a new thread from https://lkml.org/lkml/2015/12/15/663,
>> > > as
>> > > now my laptop is displaying values in the sysfs *raw* files.]
>> > >
>> > > So I'm trying to understand exactly how the hid-sensor-accel-3d
>> > > driver works.
>> > >
>> > > If I turn up debugging, when I `cat
>> > > /sys/bus/iio/devices/device*/*raw*`, I see "iio iio:device3:
>> > > accel_3d_proc_event" and I think that means that
>> > > hid_sensor_push_data() is getting called.
>> > >
>> > > But read()'s on /dev/iio:device3 never produces anything, which
>> > > is
>> > > what iio-sensor-proxy uses to translate events to dbus.
>> > >
>> > > Is it expected that the dev-node is "silent"? Just trying to
>> > > understand if an extension to the driver to support a chardev
>> > > based
>> > > output is appropriate, or if iio-sensor-proxy needs to be changed
>> > > to
>> > > handle this device.
>> >
>> > You are saying there is some regression. This used to work and now
>> > it
>> > doesn't work. Is raw values are displayed correctly, when you do
>> > "cat"?
>> > If cat of raw values is working then power on of sensors is
>> > working.
>>
>> Sorry, I was unclear. I don't know if this is a regression. I can try
>> going back to an older kernel to see if the /dev/iio:device* files
>> produced any output.
>>
>> Yes, the *raw* files in sysfs are producing output, that is changing
>> as I move the laptop around. But the /dev/ nodes seem to produce no
>> output (I'm still reading through the driver code to understand where
>> that data should be coming from.
>>
>> > Turn on HID debug prints. If it is regression we can do git bisect.
>> > Any ACPI or PM changes can break this. Usually there will be GPIOs
>> > which will be involved in power on, where ACPI comes into play.
>> > This
>> > will be done by i2c-hid. There are some prints in i2c-hid which can
>> > be
>> > enabled also.
>>
>> Ok, I will try this, as well.
>>
>
> Try increasing in_accel_sampling_frequency
> echo 100 > in_accel_sampling_frequency
> Adjust hysteresis to a low value
> echo 0 > in_accel_hysteresis
> These values are very vendor specific.

Adjusting the values in this way didn't seem to make any difference.
Also, `cat in_accel_hysteresis` gave EINVAL, but I was able to echo 0
to it.

-Nish
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