Hi Michael, On Sat, Mar 28, 2015 at 6:11 PM, Michael Leuchtenburg <michael@xxxxxxxxxxxxx> wrote: > I have been trying to figure out how to get palm detection working on > my new Dell XPS 13 9343. It has a Windows Precision Touchpad (PTP) > compliant touchpad; I think it's a Synaptics rebrand. DLL0665:01 > 06CB:76AD UNKNOWN; that 06CB definitely indicates it's Synaptics under > there. > > I've been trying to figure out if it's not sending information along > that could be used to determine if a touch is intentional or > unintentional or if the Linux drivers - either kernel or userspace - > just don't support what it's sending. PTP devices must send at least > "confidence", which is used to indicate that a touch is not a finger. > They may also send width and height which could be used for detection. > It doesn't look like confidence is supported by Linux currently. Oh. It looks like I should have spent more time looking into this spec. I did not notice that Confidence know has a palm rejection meaning. Sigh. For touchscreens, this used to be that until the bit is set, the touch might not be an actual touch... > > In trying to figure this out, I looked at the HID descriptor and > noticed that it's not reporting itself as a PTP but rather as a mouse. > This is actually as expected for an PTP compliant device which hasn't > been initialized fully - according to > https://msdn.microsoft.com/en-us/library/windows/hardware/dn467314(v=vs.85).aspx > devices are supposed to use the Mouse Collection for input reporting > until the input mode is set to touchpad, after which they're supposed > to switch to the Windows Precision Touchpad Collection. > > It looks like the hid-multitouch driver generally doesn't set the > input mode on devices to MT_INPUTMODE_TOUCHPAD (0x3). By default it > sets it to MT_INPUTMODE_TOUCHSCREEN (0x2) in mt_probe. It does also > set it to MT_INPUTMODE_TOUCHAD (0x3) in mt_touch_input_mapping, though > I haven't traced through to see if that actually gets written out to > the device or is just used by the driver to determine how to interpret > various events. Well, we do not export the mouse collection, so I can guarantee that we are using the PTP collection :) You can also be sure by checking at the input node, by running evemu-record, and you'll see that we forward the raw touches (like a touchscreen), and not the relative axes (like any plain mouse). > > Have I missed something? Is it actually being initialized to PTP mode > and rdesc just isn't being updated? That would probably lead to > misinterpreting some events since the event collections are very > different, so it seems unlikely. Is there some condition under which > it does get initialized to PTP mode? No, I think you misread the report descriptors. There should be at least 2 collections, one for the mouse and one for the raw touchpad. We do not change the report descriptors in hid-multitouch so it should still be there. > > If I'm right and this mode just isn't supported currently, is anyone > working on this functionality? I'd rather not duplicate effort. The chromium guys just got their MT_TOOL_PALM patch merged in Dmitri's tree: https://git.kernel.org/cgit/linux/kernel/git/dtor/input.git/commit/?h=for-linus&id=a736775db683174269c65c7c5cc8e5ee534e7681 I don't know if they plan to make hid-multitouch aware of it, but that seems legitimate to me. You are welcome to work on such patches :) Cheers, Benjamin -- 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
