A number of messages around the net have observed that the Magic Mouse
peripheral only distinguishes between left and right clicks, doesn't
emulate a scroll wheel, etc.
The multitouch input data from the mouse uses a proprietary format[1] --
the HID report descriptor lists X, Y, button, battery and a 64-byte
usage on a vendor-specific usage page -- so it doesn't parse using a
standard HID parser.
My questions:
How do I know whether it's easier to write this as a heavily customized
HID driver or a generic input driver (one which happens to talk to a
Bluetooth HID device)?
The mouse reports when it stops seeing a reflection from its laser. How
should that be passed to applications?
Because the mouse can only classify clicks based on touch position, a
driver might as well classify clicks for three buttons. Would there be
objections to a driver having a writable parameter to make it emulate a
three-button mouse instead of a two-button mouse?
Similarly, would there be objections to a driver having a writable
parameter to make it emulate a scroll wheel?
Is there a plan for some higher level to perform middle-click or scroll
wheel emulation rather than have each driver do the work? (It seems
plausible that other touch-sensitive hardware has the same limit.)
[1]- Except for __le24 not existing, the touch data has to be enabled by
sending HID SET_REPORT sequences, and the data looks approximately like
this, using report 0x29:
struct magic_mouse_touch {
__s8 x;
__s8 y;
__le24 timestamp_and_buttons;
struct {
__le24 x_y;
__u8 probably_minor_length;
__u8 apparently_major_length_and_flags;
__u8 angle;
__u8 state_and_touch_id;
} touch[];
};
where the two lsbs of the timestamp_and_buttons contain 0, 1 or 2 to
indicate inferred click type, and the touch[] array can range from 0 to
at least 4 elements. I'm not 100% sure about the format or meaning of
the two axis length bytes. The SET_REPORT enable byte sequences are
0x53, 0xd7, 0x01 and 0x53, 0xf8, 0x01, 0x32 respectively -- 0x53 being
the Bluetooth HID binding value for SET_REPORT with type Feature; I'm
not sure about the other bytes.
Michael Poole
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