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With v6.11+, we can actually call hid_hw_output_report() and put the device into raw mode, thus getting accurate events without being messed up. Technically we could do the same on v6.10, but given that wayland, gnome and KDE are still not capable of handling the dial, and that v6.10 is EOL, we can safely save a little bit of compilation by only allowing v6.11+. We can easily export the battery information to userspace by adding a dedicated report. However, we need to cheat on the kernel to force it not to query the battery by making the physical collection a stylus. The kernel will then only rely on the events it gets from the device. Link: https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/133 Acked-by: Jiri Kosina <jkosina@suse.com> Link: https://patch.msgid.link/20250207-bpf-import-2025-02-07-v1-7-6048fdd5a206@kernel.org Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
# HID-BPF programs
This directory contains various fixes for devices. They add new features or
fix some behaviors without being entirely mandatory. It is better to load them
when you have such a device, but they should not be a requirement for a device
to be working during the boot stage.
The .bpf.c files provided here are not automatically compiled in the kernel.
They should be loaded in the kernel by `udev-hid-bpf`:
https://gitlab.freedesktop.org/libevdev/udev-hid-bpf
The main reasons for these fixes to be here is to have a central place to
"upstream" them, but also this way we can test them thanks to the HID
selftests.
Once a .bpf.c file is accepted here, it is duplicated in `udev-hid-bpf`
in the `src/bpf/stable` directory, and distributions are encouraged to
only ship those bpf objects. So adding a file here should eventually
land in distributions when they update `udev-hid-bpf`
## Compilation
Just run `make`
## Installation
### Automated way
Just run `sudo udev-hid-bpf install ./my-awesome-fix.bpf.o`
### Manual way
- copy the `.bpf.o` you want in `/etc/udev-hid-bpf/`
- create a new udev rule to automatically load it
The following should do the trick (assuming udev-hid-bpf is available in
/usr/bin):
```
$> cp xppen-ArtistPro16Gen2.bpf.o /etc/udev-hid-bpf/
$> udev-hid-bpf inspect xppen-ArtistPro16Gen2.bpf.o
[
{
"name": "xppen-ArtistPro16Gen2.bpf.o",
"devices": [
{
"bus": "0x0003",
"group": "0x0001",
"vid": "0x28BD",
"pid": "0x095A"
},
{
"bus": "0x0003",
"group": "0x0001",
"vid": "0x28BD",
"pid": "0x095B"
}
],
...
$> cat <EOF > /etc/udev/rules.d/99-load-hid-bpf-xppen-ArtistPro16Gen2.rules
ACTION!="add|remove", GOTO="hid_bpf_end"
SUBSYSTEM!="hid", GOTO="hid_bpf_end"
# xppen-ArtistPro16Gen2.bpf.o
ACTION=="add",ENV{MODALIAS}=="hid:b0003g0001v000028BDp0000095A", RUN{program}+="/usr/local/bin/udev-hid-bpf add $sys$devpath /etc/udev-hid-bpf/xppen-ArtistPro16Gen2.bpf.o"
ACTION=="remove",ENV{MODALIAS}=="hid:b0003g0001v000028BDp0000095A", RUN{program}+="/usr/local/bin/udev-hid-bpf remove $sys$devpath "
# xppen-ArtistPro16Gen2.bpf.o
ACTION=="add",ENV{MODALIAS}=="hid:b0003g0001v000028BDp0000095B", RUN{program}+="/usr/local/bin/udev-hid-bpf add $sys$devpath /etc/udev-hid-bpf/xppen-ArtistPro16Gen2.bpf.o"
ACTION=="remove",ENV{MODALIAS}=="hid:b0003g0001v000028BDp0000095B", RUN{program}+="/usr/local/bin/udev-hid-bpf remove $sys$devpath "
LABEL="hid_bpf_end"
EOF
$> udevadm control --reload
```
Then unplug and replug the device.
## Checks
### udev rule
You can check that the udev rule is correctly working by issuing
```
$> udevadm test /sys/bus/hid/devices/0003:28BD:095B*
...
run: '/usr/local/bin/udev-hid-bpf add /sys/devices/virtual/misc/uhid/0003:28BD:095B.0E57 /etc/udev-hid-bpf/xppen-ArtistPro16Gen2.bpf.o'
```
### program loaded
You can check that the program has been properly loaded with `bpftool`
```
$> bpftool prog
...
247: tracing name xppen_16_fix_eraser tag 18d389353ed2ef07 gpl
loaded_at 2024-03-28T16:02:28+0100 uid 0
xlated 120B jited 77B memlock 4096B
btf_id 487
```