Re: "i2c_hid: Could not register for interrupt, irq = -1" on Thinkpad Tablet 10

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On Mon, Feb 2, 2015 at 10:32 AM, Sébastien Bourdeauducq <sb@xxxxxxxxx> wrote:
> On 02/02/2015 09:48 PM, Mika Westerberg wrote:
>> On Mon, Feb 02, 2015 at 09:19:51PM +0800, Sebastien Bourdeauducq wrote:
>>> With this computer nothing is normal. Every single component except the CPU,
>>> display and USB has major issues under Linux.
>>
>> We need to get one here then. Can you point me to the exact model?
>
> That's a Lenovo Thinkpad Tablet 10, P/N 20C3001VHH. What would be the
> plan for you to get one?
>
>> Since it has 20k internal pull-up configured, I'm guessing something
>> (the digitizer) drives it low like it still has something to report. Do
>> you see in the dmesg if the i2c-hid.c is able to read reports from the
>> device?
>
> When I made the interrupt falling edge sensitive, i2c-hid was able to
> read the first report as I could move the mouse cursor once using the
> stylus.
>
> A possible scenario is:
> 1) the digitizer is holding the interrupt line low after booting
> 2) enumerating or otherwise initializing the digitizer causes it to
> release the interrupt line
> 3) using the stylus queues several reports in the device and it asserts
> the interrupt line again. However, with the interrupt configured as edge
> sensitive, only the first of those reports are retrieved and subsequent
> ones are lost, with the interrupt line stuck.

There has been a patch floating around last year which tried to pull
all the available reports after the IRQ was triggered. I rejected it
for the sake of not breaking existing devices, but maybe your device
needs it.
http://www.spinics.net/lists/linux-input/msg31342.html

Cheers,
Benjamin

>
> Maybe the interrupt should be level sensitive and enabled only after
> certain parts of the device initialization have taken place.
>
> Sébastien
>
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