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

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Message-ID: <1450400953.5427.18.camel@intel.com>
Date:	Fri, 18 Dec 2015 01:11:01 +0000
From:	"Pandruvada, Srinivas" <srinivas.pandruvada@...el.com>
To:	"nish.aravamudan@...il.com" <nish.aravamudan@...il.com>
CC:	"lars@...afoo.de" <lars@...afoo.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"knaack.h@....de" <knaack.h@....de>,
	"jic23@...nel.org" <jic23@...nel.org>,
	"cmo@...exis.com" <cmo@...exis.com>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"pmeerw@...erw.net" <pmeerw@...erw.net>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"jikos@...nel.org" <jikos@...nel.org>,
	"Shevchenko, Andriy" <andriy.shevchenko@...el.com>
Subject: Re: iio/hid-sensor-accel-3d: no output from /dev/iio:device*?

On Thu, 2015-12-17 at 17:08 -0800, Nish Aravamudan wrote:
> On Thu, Dec 17, 2015 at 5:00 PM, Pandruvada, Srinivas
> <srinivas.pandruvada@...el.com> wrote:
> > Hi Andy,
> > 
> > As per Nish these patches are impacting sensors on Yoga.
> > https://lkml.org/lkml/2015/11/30/441
> 
> To be clear, without that series, the touchpad and touchscreen on the
> Yoga 900 don't work at all. So they are necessary for functioning. I
> don't know (I will test it now), if removing the series makes the IIO
> sensors work properly in /dev/.
This is important to know before we take Andy's time.

Thanks,
Srinivas

> 
> -Nish
> 
> > On Thu, 2015-12-17 at 16:51 -0800, Srinivas Pandruvada 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.
> > > 
> > > 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.
> > > 
> > > Thanks,
> > > Srinivas
> > > 
> > > >