> > I believe there is a strong userspace assumption that BTN_TOOL_* has > > no meaning for real MT devices. Rightfully so, IMO. Hence, I think > > semi-mt needs to be used here as well. > > I think we need to adjust userspace to pay attention to BTN_TOOL_* for > MT-B too so that if number of slots advertised does not match > BTN_TOOL_* capabilities that means that the device does not privide > tracking data for all contacts. Well, it is possible, but it is a great deal more complex than just looking at what the slots contain. At least we should all be able to agree that MT-B is sufficient for any "proper" MT device. > Luckily this should be backward-compatible (i.e. older userspace will > ignore "extended" fingercounts, newer will pay attention to it). OTOH, letting semi-mt engulf all devices which requires the use of BTN_TOOL_* for finger count makes it easier to differentiate between various userspace support levels. "This app supports pure MT-B only", etc. > > > This is the best option in my opinion. We will present 2 finger position > > > data plus extended finger count. > > > > We never did put all the details of the bounding box coordinates in > > writing, so perhaps this is an opportunity to both fix that and extend > > usability to the case so described. The only question is whether there > > are applications out there which now assume min/max instead of contact > > positions. If anyone knows, please speak up. :-) Otherwise, I am very > > much for Daniel's case C, with Dmitry's modification. > > > > In short: Use the semi-MT property, and send two suitable fingers > > along with it. > > Umm... but it is my understanding that 2 fingers will provide real > tracking data, not bounding box, so why would we set semi-MT? To indicate that a) the two positions may not represent true fingers but a bounding box, and b) the contact count is determined by BTN_TOOL_*. True, there is no way to distinguish between the real-fingers and bounding-box cases here (that is why I suggested another binary value in a previous mail), but without semi-mt, there is no way to know a priori if special logic is needed for the number of fingers. > Maybe we have different notions of what semi-MT property conveys? For me > semi-MT indicates that the device provides 2 coordinates for bounding > box. However if semi-MT is not set does not mean that the device > provides true tracking for all contacts, but only for advertised slots. > There still may be additional data transmitted. Yes, it seems we do have different assumptions here. The more reason to document it further. :-) To me, it seems we do need a little bit of extra information to determine this new type of device. Thanks, Henrik -- 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
