linux-kernel - Re: [PATCH] input: mt: Interface and MT

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Date:	Fri, 10 Dec 2010 13:17:32 -0800
From:	Ping Cheng <pinglinux@...il.com>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jiri Kosina <jkosina@...e.cz>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] input: mt: Interface and MT_TOOL documentation updates

On Fri, Dec 10, 2010 at 12:01 PM, Henrik Rydberg <rydberg@...omail.se> wrote:
> On 12/10/2010 08:00 PM, Ping Cheng wrote:
>
>> On Fri, Dec 10, 2010 at 10:13 AM, Henrik Rydberg <rydberg@...omail.se> wrote:
>>>
>>>> Can we make MT_TOOL_ENVELOPE cover a bit more cases by:
>>>>
>>>> 1. Removing ", and is only used for legacy hardware";
>>>> 2. Adding "Or the number of contacts inside the bounding rectangle is
>>>> reported if hardware provides the number but not the real contact
>>>> positions" to the end of the paragraph.
>>>
>>> You might disagree, but "old" is still somewhat apt in this situation.
>>
>> It's ok if we say the new type was inspired by legacy hardware. But
>> saying that it "is only used for legacy hardware" closes the door for
>> future development. That's not what we are trying to do, right?
>
>
> Well, in a sense we are. I would agree that data aiming to provide gestures as a
> 2D transformation matrix can be handled quite well with two tracked points and a
> finger count. However, a multitouch interface where users manipulate different
> objects on the screen simultaneously is a different story.
>
>>
>>> How would you suggest we report the number of fingers?
>>
>> I guess if we want to make it generic, we could have something like
>> ABS_MT_NUM_CONTACTS to go with MT_TOOL_ENVELOPE. Clients, such as
>> synaptics touchpads, that only care about the number of contacts
>> inside the envelope don't need to process the contact positions even
>> when they are reported. This also resolve the potential that
>> BTN_TOOL_QUADTAP is not enough to tell us how many contacts are on the
>> surface.
>
>
> I really would like to avoid adding a new way to solve an old problem, in
> particular given the statement above. Adding something like BTN_TOOL_QUINTAP
> would hurt a little bit, but not nearly as much.

If we plan to add BTN_TOOL_QUINTAP, you can ignore my previous comments.

>> Maybe we should also tell the clients whether they are going to get
>> the contact positions or not.
>
>
> I may not understand what you mean here, but if you are referring to an up-front
> declaration of what MT_TOOL types are to be expected, we did discuss this
> before, without any conclusion. Perhaps it is relevant to outline why this would
> be important.

With BTN_TOOL_QUINTAP, this question can be ignored too.

Thank you.

Ping
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