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

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Message-ID: <CAOhV88OinTE31-qp1vh-4XHT-TqMTTOYwHiLk0yptg0prwetjw@mail.gmail.com>
Date:	Thu, 17 Dec 2015 17:08:40 -0800
From:	Nish Aravamudan <nish.aravamudan@...il.com>
To:	"Pandruvada, Srinivas" <srinivas.pandruvada@...el.com>
Cc:	"jikos@...nel.org" <jikos@...nel.org>,
	"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>,
	"Shevchenko, Andriy" <andriy.shevchenko@...el.com>
Subject: Re: iio/hid-sensor-accel-3d: no output from /dev/iio:device*?

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/.

-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
>>
>> >
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