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    SubjectRe: [RFC][PATCH] input: Introduce device information ioctl
    On Tue, Dec 07, 2010 at 01:18:41PM -0600, Chris Bagwell wrote:
    > On Tue, Dec 7, 2010 at 1:25 AM, Henrik Rydberg <rydberg@euromail.se> 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.
    > >
    > > Suggested-by: Dmitry Torokhov <dtor@mail.ru>
    > > Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
    > > Cc: Ping Cheng <pingc@wacom.com>
    > > Cc: Chris Bagwell <chris@cnpbagwell.com>
    > > ---
    > > Hi all,
    > >
    > > Here is a patch attempting to formulate Dmitry's device type idea. It
    > > compiles, but further testing awaits a general consesus on the device
    > > types and capabilities to start out with. Are the ones listed here apt
    > > for the job?
    > >
    > > Cheers,
    > > Henrik
    > >
    > >  drivers/input/evdev.c |    6 ++++++
    > >  include/linux/input.h |   34 ++++++++++++++++++++++++++++++++++
    > >  2 files changed, 40 insertions(+), 0 deletions(-)
    > >
    > > diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
    > > index e3f7fc6..db78592 100644
    > > --- a/drivers/input/evdev.c
    > > +++ b/drivers/input/evdev.c
    > > @@ -632,6 +632,12 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
    > >                        return -EFAULT;
    > >                return 0;
    > >
    > > +       case EVIOCGDEVINFO:
    > > +               if (copy_to_user(p, &dev->devinfo,
    > > +                                sizeof(struct input_devinfo)))
    > > +                       return -EFAULT;
    > > +               return 0;
    > > +
    > >        case EVIOCGREP:
    > >                if (!test_bit(EV_REP, dev->evbit))
    > >                        return -ENOSYS;
    > > diff --git a/include/linux/input.h b/include/linux/input.h
    > > index 6ef4446..8c58d2a 100644
    > > --- a/include/linux/input.h
    > > +++ b/include/linux/input.h
    > > @@ -57,6 +57,21 @@ struct input_absinfo {
    > >  };
    > >
    > >  /**
    > > + * struct input_devinfo - device information via EVIOCGDEVINFO ioctl
    > > + * @types: bitmask of types (DEVTYPE_*) matching this device
    > > + * @capabilities: bitmask of capabilities (DEVCAPS_*) of this device
    > > + *
    > > + * This struct provides information about the device needed for
    > > + * automatic setup in userspace, such as if the device is direct
    > > + * (touchscreen) or indirect (touchpad), and if there are other
    > > + * special considerations, such as the touchpad also being a button.
    > > + */
    > > +struct input_devinfo {
    > > +       __u32 types;
    > > +       __u32 capabilities;
    > > +};
    > > +
    >
    > "types" sounds like it can support being more then one thing at a time
    > but I don't think that is intent from below names. Should rename to
    > "type"?

    I'd be wary of restricting device to be only one type. There are some
    that are mutually exclusive (toucscreen/touchpad/tablet) but I'd leave
    option of mixed-type devices open.

    --
    Dmitry
    --
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