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    SubjectRe: [RFC][PATCH] input: Introduce device information ioctl
    On Tue, Dec 7, 2010 at 13:40, Arnd Bergmann <> wrote:
    > On Tuesday 07 December 2010, Kay Sievers wrote:
    >> On Tue, Dec 7, 2010 at 10:16, Dmitry Torokhov <> 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. Sysfs should be good enough for such
    >> interface though.
    > Please never add any ioctls that have a version or length field!
    > Ideally ioctls should have only scalar arguments, not structures,
    > so I'd recommend splitting it into two, so you can read type and
    > capability parameters separately.

    Please don't add new ioctls with a single value only. :) That's what
    sysfs is for, today.

    The problem is that sysfs or ioctls with a single value can not handle
    atomic queries of multiple values, and (rightfully) needing that in
    some cases is a reason to add an ioctl() instead of sysfs.


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      Last update: 2010-12-07 13:53    [W:0.020 / U:5.168 seconds]
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