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Message-ID: <20101207105620.GB23729@core.coreip.homeip.net>
Date: Tue, 7 Dec 2010 02:56:20 -0800
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Kay Sievers <kay.sievers@...y.org>
Cc: Henrik Rydberg <rydberg@...omail.se>,
Jiri Kosina <jkosina@...e.cz>, linux-input@...r.kernel.org,
linux-kernel@...r.kernel.org, Ping Cheng <pingc@...om.com>,
Chris Bagwell <chris@...bagwell.com>
Subject: Re: [RFC][PATCH] input: Introduce device information ioctl
On Tue, Dec 07, 2010 at 11:48:28AM +0100, Kay Sievers wrote:
> On Tue, Dec 7, 2010 at 10:16, Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> > Hi Henrik,
> >
> > On Tue, Dec 07, 2010 at 08:25:26AM +0100, Henrik Rydberg wrote:
> >> Today, userspace sets up an input device based on the data it emits.
> >> This is not always enough; a tablet and a touchscreen may emit exactly
> >> the same data, for instance, but the former should be set up with a
> >> pointer whereas the latter does not need to. Recently, a new type of
> >> touchpad has emerged where the buttons are under the pad, which changes
> >> handling logic without changing the emitted data. This patch introduces
> >> a new ioctl, EVIOCGDEVINFO, which allows userspace to extract information
> >> about the device resulting in proper setup.
> >
> > If we agree that the new ioctl is suitable we'llalso need to wireit up
> > through sysfs. Also, can we keep all definitions to INPUT_ namespace?
>
> Please don't add new ioctls which are not extensible. The ioctl should
> carry the length or the version of the structure it asks for, so it
> can be extended in the future.
Size of ioctl data is encoded in ioctl, it can be extended easily. For
examples take a look at how EVIOCGKEYCODE and EVIOCGSKEYCODE are handled
in recent kernels.
> Sysfs should be good enough for such
> interface though.
>
--
Dmitry
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