[PATCH libinput] evdev: allow weird multitouch device without slots

[Peter Hutterer]

On Tue, Aug 19, 2014 at 06:29:40AM +0300, Leonid Borisenko wrote:
> HID device 'USB HID v1.11 Mouse' provided by Microsoft Wireless Optical
> Desktop® 2.20 (connected to USB and identified as vendor 0x45e, product
> 0xe3, version 0x111) is reported as supporting EV_ABS event with ABS_MT_SLOT
> code, but nevertheless libevdev_get_num_slots returns -1.

yeah, that's intentional. libevdev detects those devices (through guesswork,
but still...) and returns -1 as slot number.

> Furthermore, all connected devices (mouse and keyboard) don't produce any
> EV_ABS events for that HID Mouse device in tests with evtest.
> 
> Before this fix mouse didn't work in Weston (but worked in X.Org).
> 
> As partially explained by LKML message [1] (Message-Id [2]):
> 
>     The root of the problem comes from hid-input, which maps unknown axis
>     to ABS_MISC. However, when an event code is already in use, hid-input
>     uses the one after, leading to uses of ABS_MISC + N, where N is the
>     number of unknown axis.
> 
>     We are encountering a problem with the multitouch protocol here because
>     if a device has more than 7 unknown axis (which is the case for the PS3
>     Sixaxis controller), then the unknown axis get maps to ABS_MT_SLOT and
>     beyond.
> 
> [1] https://lkml.org/lkml/2013/11/20/515
> [2] 1384983141-31019-1-git-send-email-benjamin.tissoires at redhat.com
> 
> Signed-off-by: Leonid Borisenko <leo.borisenko at gmail.com>
> ---
>  src/evdev.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/src/evdev.c b/src/evdev.c
> index a125510..d6a14b7 100644
> --- a/src/evdev.c
> +++ b/src/evdev.c
> @@ -144,7 +144,7 @@ evdev_flush_pending_event(struct evdev_device *device, uint64_t time)
>  		pointer_notify_motion(base, time, motion.dx, motion.dy);
>  		break;
>  	case EVDEV_ABSOLUTE_MT_DOWN:
> -		if (!(device->seat_caps & EVDEV_DEVICE_TOUCH))
> +		if (slot == -1 || !(device->seat_caps & EVDEV_DEVICE_TOUCH))
>  			break;
>  
>  		if (device->mt.slots[slot].seat_slot != -1) {
> @@ -167,7 +167,7 @@ evdev_flush_pending_event(struct evdev_device *device, uint64_t time)
>  		touch_notify_touch_down(base, time, slot, seat_slot, x, y);
>  		break;
>  	case EVDEV_ABSOLUTE_MT_MOTION:
> -		if (!(device->seat_caps & EVDEV_DEVICE_TOUCH))
> +		if (slot == -1 || !(device->seat_caps & EVDEV_DEVICE_TOUCH))
>  			break;
>  
>  		seat_slot = device->mt.slots[slot].seat_slot;
> @@ -180,7 +180,7 @@ evdev_flush_pending_event(struct evdev_device *device, uint64_t time)
>  		touch_notify_touch_motion(base, time, slot, seat_slot, x, y);
>  		break;
>  	case EVDEV_ABSOLUTE_MT_UP:
> -		if (!(device->seat_caps & EVDEV_DEVICE_TOUCH))
> +		if (slot == -1 || !(device->seat_caps & EVDEV_DEVICE_TOUCH))
>  			break;
>  
>  		seat_slot = device->mt.slots[slot].seat_slot;
> @@ -680,6 +680,16 @@ evdev_configure_device(struct evdev_device *device)
>  				active_slot = libevdev_get_current_slot(evdev);
>  			}
>  
> +			if (num_slots <= 0) {
> +				log_bug_kernel(libinput,
> +					       "multitouch input device %s "
> +					       "has %s slots\n",
> +					       device->devnode,
> +					       num_slots == 0 ? "0" : "no");
> +				num_slots = 0;
> +				active_slot = -1;
> +			}
> +

so, as I said above the libevdev behaviour is intentional and our indicator
that this isn't a MT device after all. We should integrate that knowledge
better so that we don't label a device as touch device when it isn't, and so
that we process events from those axes as normal ABS events instead of MT
events.

Cheers,
   Peter



>  			slots = calloc(num_slots, sizeof(struct mt_slot));
>  			if (!slots)
>  				return -1;
> -- 
> 2.1.0.rc1