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

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Message-ID: <1450401390.5427.22.camel@linux.intel.com>
Date:	Thu, 17 Dec 2015 17:16:30 -0800
From:	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:	Nish Aravamudan <nish.aravamudan@...il.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, 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.

Thanks,
Srinivas

> -Nish
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