Prior to commit 190d7f02ce8e ("HID: input: do not increment usages when a duplicate is found") from the v4.18 kernel, HID used to shift the event codes if a duplicate usage was found. This ended up in a situation where a device would export a ton of ABS_MISC+n event codes, or a ton of REL_MISC+n event codes. This is now fixed, however userspace needs to detect those situation. Fortunately, ABS_MT_SLOT-1 (ABS_MISC+6) was never assigned a code, and so libinput can detect fake multitouch devices from genuine ones by checking if ABS_MT_SLOT-1 is set. Now that we have REL_WHEEL_HI_RES, libinput won't be able to differentiate true high res mice from some other device in a pre-v4.18 kernel. Set in stone that the ABS_MISC+6 and REL_MISC+1 are reserved and should not be used so userspace can properly work around those old kernels.
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| @@ -708,7 +708,15 @@ · 707 unmodified lines | ||
| 708 | 708 | #define REL_DIAL 0x07 |
| 709 | 709 | #define REL_WHEEL 0x08 |
| 710 | 710 | #define REL_MISC 0x09 |
| 711 | −#define REL_WHEEL_HI_RES 0x0a | |
| 711 | +/* | |
| 712 | + * 0x0a is reserved and should not be used in input drivers. | |
| 713 | + * It was used by HID as REL_MISC+1 and userspace needs to detect if | |
| 714 | + * the next REL_* event is correct or is just REL_MISC + n. | |
| 715 | + * We define here REL_RESERVED so userspace can rely on it and detect | |
| 716 | + * the situation described above. | |
| 717 | + */ | |
| 718 | +#define REL_RESERVED 0x0a | |
| 719 | +#define REL_WHEEL_HI_RES 0x0b | |
| 712 | 720 | #define REL_MAX 0x0f |
| 713 | 721 | #define REL_CNT (REL_MAX+1) |
| 714 | 722 | |
| @@ -745,6 +753,15 @@ · 30 unmodified lines | ||
| 745 | 753 | |
| 746 | 754 | #define ABS_MISC 0x28 |
| 747 | 755 | |
| 756 | +/* | |
| 757 | + * 0x2e is reserved and should not be used in input drivers. | |
| 758 | + * It was used by HID as ABS_MISC+6 and userspace needs to detect if | |
| 759 | + * the next ABS_* event is correct or is just ABS_MISC + n. | |
| 760 | + * We define here ABS_RESERVED so userspace can rely on it and detect | |
| 761 | + * the situation described above. | |
| 762 | + */ | |
| 763 | +#define ABS_RESERVED 0x2e | |
| 764 | + | |
| 748 | 765 | #define ABS_MT_SLOT 0x2f /* MT slot being modified */ |
| 749 | 766 | #define ABS_MT_TOUCH_MAJOR 0x30 /* Major axis of touching ellipse */ |
| 750 | 767 | #define ABS_MT_TOUCH_MINOR 0x31 /* Minor axis (omit if circular) */ |