linux-kernel - Re: [PATCH 1/2] input: touchscreen: ar1021

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Date:   Fri, 16 Feb 2018 17:38:43 +0100
From:   Christian Gmeiner <christian.gmeiner@...il.com>
To:     Martin Kepplinger <martin.kepplinger@...zinger.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input <linux-input@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] input: touchscreen: ar1021_i2c: enable touch mode
 during open

2018-02-05 11:40 GMT+01:00 Martin Kepplinger <martin.kepplinger@...zinger.com>:
>
>
>
>
> Martin Kepplinger | Entwicklung Software
>
> GINZINGER ELECTRONIC SYSTEMS GMBH
>
> Tel.: +43 7723 5422 157
> Mail: martin.kepplinger@...zinger.com
> Web: www.ginzinger.com
>
>
>
>
> On 2018-02-05 11:07, Christian Gmeiner wrote:
>> Hi all.
>>
>> 2017-04-27 14:22 GMT+02:00 Martin Kepplinger <martin.kepplinger@...zinger.com>:
>>> The device could as well be in command mode, in which this driver cannot
>>> handle the device. When opening the device, let's make sure the device
>>> will be in the mode we expect it to be for this driver.
>>>
>>
>> I run into issues caused by this change. It turns out that the device
>> is non-functional
>> after some warm-reboots and as a result I am not able to use xorg's
>> evdev driver.
>> So I have some questions about this change:
>>
>> * Should we enable irq before calling i2c_master_send(..) as the chip raises an
>>   irq if the command was processed?
>>
>> * Would it be enough to send this command only once during driver
>> lifetime? I can
>>   see that on my system open gets called 3 times during boot-up.
>
> It would. See below for my thought on this change.
>
>>
>> * What are the circumstances the touch device would be in an other state? In the
>>   official kernel driver the userspace can send commands via sysfs.
>> Also the driver
>>   does set the touch enable mode as this patch does.
>
> I did this change as the device was once non-functional unexpectedly
> because it wasn't in touch mode. We can set touch mode during open() or
> probe() but I figured during open() would keep the driver working even
> when others would use the device in command mode.
>
> Does your problem go away when you revert this change or put it into
> probe()?

I needed to postprone further research and reverted this commit locally as
a new software release gets releases soon. The good this that I have
an automated way to run a test to trigger this issue quite easily.

Will have a deeper look after release time.

-- 
greets
--
Christian Gmeiner, MSc

https://christian-gmeiner.info