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1# HID-BPF programs2 3This directory contains various fixes for devices. They add new features or4fix some behaviors without being entirely mandatory. It is better to load them5when you have such a device, but they should not be a requirement for a device6to be working during the boot stage.7 8The .bpf.c files provided here are not automatically compiled in the kernel.9They should be loaded in the kernel by `udev-hid-bpf`:10 11https://gitlab.freedesktop.org/libevdev/udev-hid-bpf12 13The main reasons for these fixes to be here is to have a central place to14"upstream" them, but also this way we can test them thanks to the HID15selftests.16 17Once a .bpf.c file is accepted here, it is duplicated in `udev-hid-bpf`18in the `src/bpf/stable` directory, and distributions are encouraged to19only ship those bpf objects. So adding a file here should eventually20land in distributions when they update `udev-hid-bpf`21 22## Compilation23 24Just run `make`25 26## Installation27 28### Automated way29 30Just run `sudo udev-hid-bpf install ./my-awesome-fix.bpf.o`31 32### Manual way33 34- copy the `.bpf.o` you want in `/etc/udev-hid-bpf/`35- create a new udev rule to automatically load it36 37The following should do the trick (assuming udev-hid-bpf is available in38/usr/bin):39 40```41$> cp xppen-ArtistPro16Gen2.bpf.o /etc/udev-hid-bpf/42$> udev-hid-bpf inspect xppen-ArtistPro16Gen2.bpf.o43[44 {45 "name": "xppen-ArtistPro16Gen2.bpf.o",46 "devices": [47 {48 "bus": "0x0003",49 "group": "0x0001",50 "vid": "0x28BD",51 "pid": "0x095A"52 },53 {54 "bus": "0x0003",55 "group": "0x0001",56 "vid": "0x28BD",57 "pid": "0x095B"58 }59 ],60...61$> cat <EOF > /etc/udev/rules.d/99-load-hid-bpf-xppen-ArtistPro16Gen2.rules62ACTION!="add|remove", GOTO="hid_bpf_end"63SUBSYSTEM!="hid", GOTO="hid_bpf_end"64 65# xppen-ArtistPro16Gen2.bpf.o66ACTION=="add",ENV{MODALIAS}=="hid:b0003g0001v000028BDp0000095A", RUN{program}+="/usr/local/bin/udev-hid-bpf add $sys$devpath /etc/udev-hid-bpf/xppen-ArtistPro16Gen2.bpf.o"67ACTION=="remove",ENV{MODALIAS}=="hid:b0003g0001v000028BDp0000095A", RUN{program}+="/usr/local/bin/udev-hid-bpf remove $sys$devpath "68# xppen-ArtistPro16Gen2.bpf.o69ACTION=="add",ENV{MODALIAS}=="hid:b0003g0001v000028BDp0000095B", RUN{program}+="/usr/local/bin/udev-hid-bpf add $sys$devpath /etc/udev-hid-bpf/xppen-ArtistPro16Gen2.bpf.o"70ACTION=="remove",ENV{MODALIAS}=="hid:b0003g0001v000028BDp0000095B", RUN{program}+="/usr/local/bin/udev-hid-bpf remove $sys$devpath "71 72LABEL="hid_bpf_end"73EOF74$> udevadm control --reload75```76 77Then unplug and replug the device.78 79## Checks80 81### udev rule82 83You can check that the udev rule is correctly working by issuing84 85```86$> udevadm test /sys/bus/hid/devices/0003:28BD:095B*87...88run: '/usr/local/bin/udev-hid-bpf add /sys/devices/virtual/misc/uhid/0003:28BD:095B.0E57 /etc/udev-hid-bpf/xppen-ArtistPro16Gen2.bpf.o'89```90 91### program loaded92 93You can check that the program has been properly loaded with `bpftool`94 95```96$> bpftool prog97...98247: tracing name xppen_16_fix_eraser tag 18d389353ed2ef07 gpl99 loaded_at 2024-03-28T16:02:28+0100 uid 0100 xlated 120B jited 77B memlock 4096B101 btf_id 487102```103