On Wed, Jul 06, 2011 at 09:31:20PM +0200, Henrik Rydberg wrote: > > > 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. Do app writers really want to exclude semi-MT devices even though they might be usable? I can see wanting to support only MT-B protocol (as opposed to chatty MT-A) but if semi-MT stream is usable why not use it? > > > > > 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 And that is the problem. > (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. This should be pretty straightforward: num_fingers = calc_fingers_from_btn_tool(device); // via EVIOCGKEY num_slots = get_number_of_slots(device); // EVIOCGABS num_untracked_contacts = max(num_fingers - num_slots, 0); > > > 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. :-) I'll take patches ;) > > To me, it seems we do need a little bit of extra information to > determine this new type of device. I think we already have all we need (see above). Thanks. -- Dmitry -- 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
