On Mon, Jun 4, 2018 at 7:33 PM, Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> wrote: > On Mon, Jun 04, 2018 at 03:18:12PM +0200, Benjamin Tissoires wrote: >> On Fri, Jun 1, 2018 at 8:43 PM, Dmitry Torokhov >> <dmitry.torokhov@xxxxxxxxx> wrote: >> > On Fri, Jun 01, 2018 at 04:16:09PM +0200, Benjamin Tissoires wrote: >> >> On Fri, Aug 11, 2017 at 2:44 AM, Dmitry Torokhov >> >> <dmitry.torokhov@xxxxxxxxx> wrote: >> >> > According to Microsoft specification [1] for Precision Touchpads (and >> >> > Touchscreens) the devices use "confidence" reports to signal accidental >> >> > touches, or contacts that are "too large to be a finger". Instead of >> >> > simply marking contact inactive in this case (which causes issues if >> >> > contact was originally proper and we lost confidence in it later, as >> >> > this results in accidental clicks, drags, etc), let's report such >> >> > contacts as MT_TOOL_PALM and let userspace decide what to do. >> >> > Additionally, let's report contact size for such touches as maximum >> >> > allowed for major/minor, which should help userspace that is not yet >> >> > aware of MT_TOOL_PALM to still perform palm rejection. >> >> > >> >> > An additional complication, is that some firmwares do not report >> >> > non-confident touches as active. To cope with this we delay release of >> >> > such contact (i.e. if contact was active we first report it as still >> >> > active MT+TOOL_PALM and then synthesize the release event in a separate >> >> > frame). >> >> >> >> I am not sure I agree with this part. The spec says that "Once a >> >> device has determined that a contact is unintentional, it should clear >> >> the confidence bit for that contact report and all subsequent >> >> reports." >> >> So in theory the spec says that if a touch has been detected as a >> >> palm, the flow of events should not stop (tested on the PTP of the >> >> Dell XPS 9360). >> >> >> >> However, I interpret a firmware that send (confidence 1, tip switch 1) >> >> and then (confidence 0, tip switch 0) a simple release, and the >> >> confidence bit should not be relayed. >> > >> > This unfortunately leads to false clicks: you start with finger, so >> > confidence is 1, then you transition the same touch to palm (use your >> > thumb and "roll" your hand until heel of it comes into contact with the >> > screen). The firmware reports "no-confidence" and "release" in the same >> > report and userspace seeing release does not pay attention to confidence >> > (i.e. it does exactly "simple release" logic) and this results in UI >> > interpreting this as a click. With splitting no-confidence >> > (MT_TOOL_PALM) and release event into separate frames we help userspace >> > to recognize that the contact should be discarded. >> >> After further thoughts, I would consider this to be a firmware bug, >> and not how the firmware is supposed to be reporting palm. >> For the precision touchpads, the spec says that the device "should >> clear the confidence bit for that contact report and all subsequent >> reports.". And it is how the Dell device I have here reports palms. >> The firmware is not supposed to cut the event stream. >> >> There is a test for that: >> https://docs.microsoft.com/en-us/previous-versions/windows/hardware/hck/dn456905%28v%3dvs.85%29 >> which tells me that I am right here for PTP. >> >> The touchscreen spec is blurrier however. > > OK, that is great to know. > >> >> > >> >> >> >> Do you have any precise example of reports where you need that feature? >> > >> > It was observed on Pixelbooks which use Wacom digitizers IIRC. >> >> Pixelbooks + Wacom means that it was likely a touchscreen. I am right >> guessing the device did not went through Microsoft certification >> process? > > That would be correct ;) At least the firmware that is shipping with > Pixlebooks hasn't, I do now if anyone else sourced these Wacom parts for > their MSWin devices. > >> >> I am in favor of splitting the patch in 2. One for the generic >> processing of confidence bit, and one for this spurious release. For >> the spurious release, I'm more in favor of explicitly quirking the >> devices in need of such quirk. > > Hmm, I am not sure about having specific quirk. It will be hard for > users to accurately diagnose the issue if firmware is broken in this way > so we could add a new quirk for a new device. One thing we can do is keep the quirked mechanism as default in hid-multitouch, but remove it in hid-core. If people need the quirk, they can just use hid-multitouch instead (talking about the long run here). However, I really believe this might only be required for a handful of devices, and probably only touchscreens. So I would be tempted to not make it default and see how many bug reports we have. > >> >> If you agree, I'll rebase your patch on top of my series as rebasing >> my series on top of yours will take more effort. > > That would be great. \o/ Cheers, Benjamin > >> >> I am trying to be cautious in the generic path because I want to merge >> the cleanest multitouch implementation in hid-core/hid-input, and >> leave all the quirks in hid-multitouch for the devices in need. >> >> Cheers, >> Benjamin >> >> > >> > Thanks. >> > >> > -- >> > Dmitry > > 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
