linux-kernel - Re: Status on hid xppen patch

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Message-ID: <20220512205952.GA8936@elementary>
Date:   Thu, 12 May 2022 22:59:52 +0200
From:   José Expósito <jose.exposito89@...il.com>
To:     Stefan Berzl <stefanberzl@...il.com>
Cc:     jikos@...nel.org, benjamin.tissoires@...hat.com, spbnick@...il.com,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Status on hid xppen patch

Hi Stefan,

A quick update on my work on XP-PEN tablets.

> > nice hearing from you. I was actually thinking of just asking if you
> > want to take my patch under your wing, since you seem to be doing a lot
> > of uclogic related work. But your idea is even better, just submitting  
> > my patch once everything has settled down seems to be the way to go.
> 
> Cool, let's do that. I'll cc you on the last batch of patches so you
> get notified when they get merged.

As promised, I cc'ed you on the last patchset, which has been merged
already.
At this point, the kernel and DIGImend have the same code.

In the meantime, in order to make the driver code as generic as
possible, I bought a couple of XP-PEN tablets. 

The tablets are the Deco Mini 4 and the Deco L, both of them are UGEE
tablets. I already had a UGEE Parblo A610 Pro tablet and after having a
look to the Windows driver traffic, I found out that after sending a
chunk of magic data to enable the tablet, it requests a string
descriptor ("uclogic_params_get_str_desc" can be used here) and the
tablets respond with their parameters.

The information is encoded, in bytes, as:

 02 + 03 - UCLOGIC_RDESC_PEN_PH_ID_X_LM
 04 + 05 - UCLOGIC_RDESC_PEN_PH_ID_Y_LM
 06      - Number of buttons
 07      - Dial present or not
 08 + 09 - UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM
 10 + 11 - Resolution

Bytes 12 and 13 are present but set to 0, probably indicating my
tablets are lacking some feature.

Could you confirm that your tablet returns similar information, please?

In case you want to have a look to the implementation, I'm working on
this branch:
https://github.com/JoseExposito/linux/commits/patch-xppen-deco-l

I had to introduce new functionalities to the templating system of the
driver, that's the reason for the KUnit tests.
The last patch is work in progress (hopefully I'll have time to finish
it this weekend), only the HID descriptors are missing.

I'll cc you when in the patchset so you can add your IDs :)

Best wishes,
Jose