linux-kernel - Re: [PATCH] input: mt: introduce MT event slots

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4BBDA555.1020003@euromail.se>
Date:	Thu, 08 Apr 2010 11:43:49 +0200
From:	Henrik Rydberg <rydberg@...omail.se>
To:	Michael Poole <mdpoole@...ilus.org>
CC:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] input: mt: introduce MT event slots

Michael Poole wrote:
[...]
> 
> How would the slot number for a contact be chosen?

The device driver determines how to use the slots. The driver calls
input_mt_slot(dev, slot), sends the data for the slot, picks another slot, and
repeats.

> If the kernel makes
> that assignment, what should a "slot" correspond to from a computer
> user's perspective? "Set[s] of identified sources" is a little vague:
> Does it mean contacts from one hand, contacts in one displayed window
> (assuming the touch surface is a screen), or something else?  (I assume
> it would not duplicate the blob or tracking IDs already defined for MT
> events.)

The slot is only used for data communication. Think of the slot as a combined,
unique identifier. For example, imagine a device driver dealing with contacts
labeled with both a USER_ID and a TRACKING_ID. The driver assigns every active
(USER_ID, TRACKING_ID) contact to a specific slot, and uses it to communicate
all changes to that contact. When the contact is destroyed (for instance by
sending a zero ABS_MT_PRESSURE on that slot), the slot is free to be used for
another contact.

> It seems like those would be important aspects of the protocol
> to document in Documentation/input/multi-touch-protocol.txt --
> otherwise, driver implementers or application developers might get it
> wrong.

Certainly.

Cheers,
Henrik

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/