linux-kernel - Re: [RFC v2] input: Introduce device information ioctl

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Message-ID: <20101220081642.GA17764@barra.redhat.com>
Date:	Mon, 20 Dec 2010 18:16:42 +1000
From:	Peter Hutterer <peter.hutterer@...-t.net>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Henrik Rydberg <rydberg@...omail.se>,
	Jiri Kosina <jkosina@...e.cz>, Ping Cheng <pingc@...om.com>,
	Chris Bagwell <chris@...bagwell.com>,
	Chase Douglas <chase.douglas@...onical.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC v2] input: Introduce device information ioctl

[sorry, mail stuck in my outbox for some reason]

On Wed, Dec 15, 2010 at 04:43:58PM -0800, Dmitry Torokhov wrote:
> On Thu, Dec 16, 2010 at 10:29:42AM +1000, Peter Hutterer wrote:
> > >  
> > >  /*
> > > + * Device properties and quirks
> > > + */
> > > +
> > > +#define INPUT_PROP_POINTER		0x00	/* needs a pointer */
> > > +#define INPUT_PROP_DIRECT		0x01	/* direct object manipulation */
> > 
> > fwiw, I think the common term for these is "direct input devices", at least
> > that's how a lot of the research literature refers to them. Might be good to
> > use the same term.
> > 
> > either way, not sure about this one.  I've worked with devices that were
> > indirect by nature but used directly. e.g. the magic touchpad could quite
> > easily be used as direct input device with an top-down projector. the
> > decision to use it as an indirect device is a UI decision.
> > Likewise, some mountable direct-touch touchscreens can be used indirectly if
> > the touchscreen isn't mounted straight on the display. This is very much a
> > setup-specific property and I'm not sure about the value of this
> > information.
> 
> All of these "props" would have no reflection on the event stream
> generated by the device, and exist solely for the benefits of userspace
> consumers to help them set up the device automatically and interpret the
> data appropriately. As such, if someone uses touchscreen as a tablet, I
> believe userspace should allow it, but at the price of manual setup.
> 
> If we start seeing cuch devices we could consider EVIOCSPROPS so
> infrastructure (udev) could adjust the properties so that upper levels
> (X) can still use the data to set up devices properly.
> 
> What do you think?

I figured it didn't have any effect on the data stream.
I think that for 95% of the devices, this information will probably be
correct and the only ones affected are rather exotic setups anyway that need
special setup. so I don't really oppose the flag, but there should be
documentation on what it means and that it only represents the assumed usage
of the device.

Cheers,
  Peter
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