On 08/18/2011 04:28 AM, Daniel Kurtz wrote: > Some devices are capable of identifying and/or tracking more contacts than > they can report to the driver. Document how a driver should handle this, > and what userspace should expect. > > Signed-off-by: Daniel Kurtz <djkurtz@xxxxxxxxxxxx> > --- > Documentation/input/multi-touch-protocol.txt | 14 ++++++++++++++ > 1 files changed, 14 insertions(+), 0 deletions(-) > > diff --git a/Documentation/input/multi-touch-protocol.txt b/Documentation/input/multi-touch-protocol.txt > index 71536e7..543101c 100644 > --- a/Documentation/input/multi-touch-protocol.txt > +++ b/Documentation/input/multi-touch-protocol.txt > @@ -65,6 +65,20 @@ the full state of each initiated contact has to reside in the receiving > end. Upon receiving an MT event, one simply updates the appropriate > attribute of the current slot. > > +Some devices identify and/or track more contacts than they can report to the > +driver. A driver for such a device should associate one type B slot with each > +contact that is reported by the hardware. Whenever the identity of the > +contact associated with a slot changes, the driver should invalidate that > +slot by changing its ABS_MT_TRACKING_ID. If the hardware signals that it is > +tracking more contacts than it is currently reporting, the driver should use > +a BTN_TOOL_*TAP event to inform userspace of the total number of contacts > +being tracked by the hardware at that moment. The driver should do this by > +explicitly sending the corresponding BTN_TOOL_*TAP event and setting > +use_count to false when calling input_mt_report_pointer_emulation(). > +The driver should only advertise as many slots as the hardware can report. > +Userspace can detect that a driver can report more total contacts than slots > +by noting that the largest supported BTN_TOOL_*TAP event is larger than the > +total number of type B slots reported in the absinfo for the ABS_MT_SLOT axis. > > Protocol Example A > ------------------ Acked-by: Chase Douglas <chase.douglas@xxxxxxxxxxxxx> Thanks a bunch Daniel! -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
