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    SubjectRe: [PATCH] input: Add a detailed multi-touch finger data report protocol
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    On Wed, 2008-11-19 at 11:37 -0500, Dmitry Torokhov wrote:
    > Hi Henrik,
    >
    > On Fri, Nov 07, 2008 at 12:15:29PM +0100, Henrik Rydberg wrote:
    > > In order to utilize the full power of the new multi-touch devices, a
    > > way to report detailed finger data to user space is needed. This patch
    > > adds a multi-touch (MT) protocol which allows drivers to report details
    > > for an arbitrary number of fingers.
    > >
    > > BTN_MT_REPORT_PACKET
    > >
    > > The driver presses this button to indicate the start of a packet of
    > > finger data. The button is released after the whole packet has been
    > > reported.
    > >
    > > BTN_MT_REPORT_FINGER
    > >
    > > The driver presses this button to indicate the start of a new
    > > finger. The button is released when the finger has been reported.
    > >
    > > In order to stay compatible with existing applications, the data
    > > reported in a finger packet must not be recognized as single-touch
    > > events. Therefore, a specific set of ABS_MT events is used instead.
    > >
    > > Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
    > > ---
    > > include/linux/input.h | 12 ++++++++++++
    > > 1 files changed, 12 insertions(+), 0 deletions(-)
    > >
    > > diff --git a/include/linux/input.h b/include/linux/input.h
    > > index b86fb55..c82dd42 100644
    > > --- a/include/linux/input.h
    > > +++ b/include/linux/input.h
    > > @@ -590,6 +590,9 @@ struct input_absinfo {
    > > #define KEY_NUMERIC_STAR 0x20a
    > > #define KEY_NUMERIC_POUND 0x20b
    > >
    > > +#define BTN_MT_REPORT_PACKET 0x210 /* report multitouch packet data */
    > > +#define BTN_MT_REPORT_FINGER 0x211 /* report multitouch finger data */
    > > +
    > > /* We avoid low common keys in module aliases so they don't get huge. */
    > > #define KEY_MIN_INTERESTING KEY_MUTE
    > > #define KEY_MAX 0x2ff
    > > @@ -642,6 +645,15 @@ struct input_absinfo {
    > > #define ABS_TOOL_WIDTH 0x1c
    > > #define ABS_VOLUME 0x20
    > > #define ABS_MISC 0x28
    > > +#define ABS_MT_TOUCH 0x30 /* Diameter of touching circle */
    > > +#define ABS_MT_TOUCH_MAJOR 0x30 /* Major axis of touching ellipse */
    > > +#define ABS_MT_TOUCH_MINOR 0x31 /* Minor axis of touching ellipse */
    > > +#define ABS_MT_WIDTH 0x32 /* Diameter of approaching circle */
    > > +#define ABS_MT_WIDTH_MAJOR 0x32 /* Major axis of approaching ellipse */
    > > +#define ABS_MT_WIDTH_MINOR 0x33 /* Minor axis of approaching ellipse */
    > > +#define ABS_MT_ORIENTATION 0x34 /* Ellipse orientation */
    > > +#define ABS_MT_POSITION_X 0x35 /* Center X ellipse position */
    > > +#define ABS_MT_POSITION_Y 0x36 /* Center Y ellipse position */
    > > #define ABS_MAX 0x3f
    > > #define ABS_CNT (ABS_MAX+1)
    > >
    >
    > Sorry for the long silence. I don't think utilizing button events for
    > this is a good idea. I'd rather just start reporting extended touch
    > events for a finger and signal end of sub-packet with something like
    > EV_SYN/SYN_MT_REPORT.

    I agree.

    Also, I'm still concerned about using elipses. I doubt very much any
    hardware will ever be reporting elipses; more likely are parallelograms,
    or trapezoids, other simple geometric figures, rather than a center with
    size and orientation.

    There are reasons Cairo uses aligned traps internally when tessellating
    figures....
    - Jim



    >
    --
    Jim Gettys <jg@laptop.org>
    One Laptop Per Child



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