Re: Wacom based devices and the mt kernel protocol.

[Rafi Rubin <rafi@seas.upenn.edu>]

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On 06/20/10 20:31, Ping Cheng wrote:
> On Sun, Jun 20, 2010 at 12:22 PM, Rafi Rubin <rafi@seas.upenn.edu> wrote:
>>>> N-Trig based devices and Stantum ones are the most compliant,
>>>
>>> That's fair since they don't need to track the fingers.
>>
>> N-Trig doesn't have hardware tracking, Stantum does.
> 
> Sorry for my ignorance. I don't have much time to keep track of what
> other devices are doing. Keeping all of my own balls rolling is more
> than enough work for me :).
> 
>>>> so Wacom situation needs to be clarified specially considering they are HID
>>>> devices (meaning similar to the others devices which respect the
>>>> protocol).
>>>
>>> Well, it is not a pure HID issue.  It is more of how we want to
>>> support MT on Linux issue.
>>
>> Side note for Ikbel, its not clear the wacom devices actually stay HID compliant
>> when the full protocol is active, and the basic modes are really basic (and not
>> very useful). As my understanding of the way HID and usb stuff communicate in
>> general, I've been growing less convinced its a protocol issue, more like an
>> initialization problem.
> 
> Thank you Rafi for explaining this issue.  Wacom tablets have a
> relatively long history, longer than the time that digitizers were
> supported on Linux. The default HID mouse protocol was introduced due
> to the history, which was required by Microsoft.... We can not change
> history, can we :)?
> 
> Wacom kept their devices consistent protocol-wise over the years.
> That's why even the modern digitizers default to the basic HID
> protocol.
> 
>> Still I'm not quite sure.
> 
> I think you've got the point.
> 
>>>> This impact very much the decision of a Linux user wanting to buy wacom mt device.
>>>
>>> I think end users have already got the Linux support from Wacom.  Can
>>> you share the specific issues that are preventing Linux end users from
>>> buying a Wacom MT devices? If I didn't misunderstand your point here,
>>> you are talking about Linux users, not Linux developers/hackers,
>>> right?
>>
>> I think normal users wanting to use linux for MT are generally frustrated and
>> confused at the moment.
> 
> Why do the end users get frustrated and confused? Can you share some
> examples from an end user's (not developer's) perspective with me?

Sorry, I've been too focused on the n-trig users.  They have been frustrated,
and I've seen from the forums that some have been playing with customized
versions of both the kernel and wacom x driver to get your two finger gestures.

I'm also projecting my own frustrations, seeing the X mt interface still not
quite set, and very little in the way of applications that use mt at all.  We're
still quite a ways away from seeing the full potential of a more hands on desktop.

>> Certainly the protocol between the wacom kernel driver
>> and the wacom user space driver is way below the level that most are following.
> 
> By "most", do you mean most MT device drivers, or most end users, or
> most developers? I am eager to bring the Wacom driver to the specific
> level.

End users, they don't tend to care about the internal protocols as long as their
programs do what they want.

>> As developers, I think we have a strong interest in seeing wacom migrate to a
>> shared protocol.  But our interests are in pushing the functionality beyond
>> what's currently available, and we just want to see everyone get equal access to
>> features as we create them.  I think to convince Ping (if he weren't already),
>> and the others working on the Wacom code, we'd have to show off some of what
>> he's going to gain by switching, and at the moment, as a community, I don't
>> think we are quite ready, maybe soon.
> 
> I do see the positive sign here. And, BTW, it is a she that you are
> talking to :).  Don't worry, you are still taking to the same person.
> So, it really doesn't matter to me. But, I don't want you to get the
> fact from someone else and to be "puzzled" :).

Um, what can I say, the hazards of interacting with just text in a language
curiously lacking in proper androgynous pronouns.  Please forgive my ignorance
particularly culturally.

>> So, Ping, consider that I and others will have cool things to show you in the
>> near future, and if you start migrating you will get some cool new functionality
>> when the two waves of progress collide.  Also, I think Henrik's B protocol has
>> some cool advantages which you've demonstrated considerable interest in.  So I
>> gather you do intend to switch when its convenient?
> 
> Why not? Do you think I am that stupid :)? To be honest, I've been
> waiting for the day for a while.

Not at all, I'm just incompetent at subtle nudging.

>>>> Ping can you clarifie the situation of wacom based devices ?
>>>
>>> What else do you need me to clarify? I am all ears and I am ready to
>>> clarify any thing that puzzles you.
>>
>> Will Wacom be moving to more than 2 finger support in the near future?  Do you
>> already have some products on the market?
> 
> No, we do not have 2+ finger devices on the market and I can not tell
> what the future would be. We'll see what it is when time comes.  Any
> more questions :)?

Nope, I think I've put my foot in it enough for the evening :-)

Rafi
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