psm(4) support for Elantech touchpads

[Vladimir Kondratyev]

On 2016-07-04 00:15, Vladimir Kondratyev wrote:
> On 2016-07-03 21:50, Matthias Apitz wrote:
>> Hello Vladimir,
>> 
>> I own an Acer C720 (aka Chromebook) which worked fine concerning the
>> touchpad with the cyapa driver in CURRENT. After a repair in Acer.com
>> they said that they have had to change the keyboard and the touchpad 
>> and
>> it now does not attach anymore to the cyapa.ko; it seems that it was
>> replace by an Elan TP and while googlöing for support I found your
>> posting from September 2015. I have applied the patch to r292778 but 
>> the
>> code is not walked through because it says on verbose boot:
>> 
>> atkbd0: [GIANT-LOCKED]
>> random: harvesting attach, 8 bytes (4 bits) from atkbd0
>> psm0: unable to allocate IRQ
>> 
>> Any ideas about this? Thanks in advance
>> 
>> 	matthias
> 
> Hi, Matthias
> 
> I`m afraid that device resource management is not what I`m familiar 
> with. Sorry.
> Mouse type detection starts 200 lines below IRQ initialization so this
> message should not depend on my patch.
> Quick googling shows that this is most probably an ACPI issue but that
> all I was able to find
> 
> WBR, Vladimir Kondratyev
> 

After some investigations its turned out that some modern ElanTPs use 
I2C interface not PS/2
so they can not be handled with my patch. Its necessary to port new 
driver from Linux
https://lwn.net/Articles/496137/ or from OpenBSD where it has name 
imt(4)