From: Arnd Bergmann <arnd@arndb.de>
To: Kay Sievers <kay.sievers@vrfy.org>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Henrik Rydberg <rydberg@euromail.se>,
Jiri Kosina <jkosina@suse.cz>,
linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
Ping Cheng <pingc@wacom.com>,
Chris Bagwell <chris@cnpbagwell.com>
Subject: Re: [RFC][PATCH] input: Introduce device information ioctl
Date: Tue, 7 Dec 2010 13:55:08 +0100 [thread overview]
Message-ID: <201012071355.08714.arnd@arndb.de> (raw)
In-Reply-To: <AANLkTi=Av1N2URqpgrAUCreFoJXb6ZtEkkgp_Jo4BgRw@mail.gmail.com>
On Tuesday 07 December 2010, Kay Sievers wrote:
> >> Oh, how does that work? With the ioctl call, userspace has to supply
> >> the size it expects to be returned from the kernel. How does the
> >> kernel otherwise know how much it is allowed to copy to the user?
> >
> > The ioctl command number itself is calculated from the size of the
> > data that gets passed:
> >
> > #define EVIOCGDEVINFO _IOR('E', 0x09, struct input_devinfo)
> >
> > If struct input_devinfo ever changes (which it can, but should not),
> > the command changes as well.
>
> So unlike statet, it's not extensible, and this struct and this ioctl
> can never change?
Exactly. We have plenty of unused ioctl numbers free though.
Arnd
next prev parent reply other threads:[~2010-12-07 12:55 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-07 7:25 [RFC][PATCH] input: Introduce device information ioctl Henrik Rydberg
2010-12-07 9:16 ` Dmitry Torokhov
2010-12-07 10:48 ` Kay Sievers
2010-12-07 10:56 ` Dmitry Torokhov
2010-12-07 11:19 ` Kay Sievers
2010-12-07 12:44 ` Arnd Bergmann
2010-12-07 12:52 ` Kay Sievers
2010-12-07 12:55 ` Arnd Bergmann [this message]
2010-12-07 12:40 ` Arnd Bergmann
2010-12-07 12:49 ` Kay Sievers
2010-12-07 16:51 ` Dmitry Torokhov
2010-12-07 19:57 ` Henrik Rydberg
2010-12-08 6:02 ` Dmitry Torokhov
2010-12-08 19:04 ` Henrik Rydberg
2010-12-09 9:25 ` Dmitry Torokhov
2010-12-07 16:22 ` Greg KH
2010-12-07 16:48 ` Dmitry Torokhov
2010-12-07 18:48 ` Ping Cheng
2010-12-07 19:35 ` Dmitry Torokhov
2010-12-07 19:18 ` Chris Bagwell
2010-12-07 19:37 ` Dmitry Torokhov
2010-12-08 20:26 ` Valdis.Kletnieks
2010-12-08 20:37 ` Henrik Rydberg
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