Re: [PATCH 02/18] HID: bpf: add first in-tree HID-BPF fix for the XPPen Artist 24
From: Benjamin Tissoires
Date: Thu Apr 11 2024 - 03:11:24 EST
On Apr 10 2024, Benjamin Tissoires wrote:
> This commit adds a fix for XPPen Artist 24 where the second button on
> the pen is used as an eraser.
>
> It's a "feature" from Microsoft, but it turns out that it's actually
> painful for artists. So we ship here a HID-BPF program that turns this
> second button into an actual button.
>
> Note that the HID-BPF program is not directly loaded by the kernel itself
> but by udev-hid-bpf[0]. But having the sources here allows us to also
> integrate tests into tools/testing/selftests/hid to ensure the HID-BPF
> program are actually tested.
>
> [0] https://gitlab.freedesktop.org/libevdev/udev-hid-bpf
>
> Signed-off-by: Benjamin Tissoires <bentiss@xxxxxxxxxx>
> ---
> drivers/hid/bpf/progs/Makefile | 91 +++++++++++
> drivers/hid/bpf/progs/README | 102 +++++++++++++
> drivers/hid/bpf/progs/XPPen__Artist24.bpf.c | 229 ++++++++++++++++++++++++++++
> drivers/hid/bpf/progs/hid_bpf.h | 15 ++
> drivers/hid/bpf/progs/hid_bpf_helpers.h | 170 +++++++++++++++++++++
> 5 files changed, 607 insertions(+)
>
> diff --git a/drivers/hid/bpf/progs/Makefile b/drivers/hid/bpf/progs/Makefile
> new file mode 100644
> index 000000000000..63ed7e02adf1
> --- /dev/null
> +++ b/drivers/hid/bpf/progs/Makefile
> @@ -0,0 +1,91 @@
> +# SPDX-License-Identifier: GPL-2.0
> +OUTPUT := .output
> +abs_out := $(abspath $(OUTPUT))
> +
> +CLANG ?= clang
> +LLC ?= llc
> +LLVM_STRIP ?= llvm-strip
> +
> +TOOLS_PATH := $(abspath ../../../../tools)
> +BPFTOOL_SRC := $(TOOLS_PATH)/bpf/bpftool
> +BPFTOOL_OUTPUT := $(abs_out)/bpftool
> +DEFAULT_BPFTOOL := $(BPFTOOL_OUTPUT)/bootstrap/bpftool
> +BPFTOOL ?= $(DEFAULT_BPFTOOL)
> +
> +LIBBPF_SRC := $(TOOLS_PATH)/lib/bpf
> +LIBBPF_OUTPUT := $(abs_out)/libbpf
> +LIBBPF_DESTDIR := $(LIBBPF_OUTPUT)
> +LIBBPF_INCLUDE := $(LIBBPF_DESTDIR)/include
> +BPFOBJ := $(LIBBPF_OUTPUT)/libbpf.a
> +
> +INCLUDES := -I$(OUTPUT) -I$(LIBBPF_INCLUDE) -I$(TOOLS_PATH)/include/uapi
> +CFLAGS := -g -Wall
> +
> +VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux) \
> + $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux) \
> + ../../../../vmlinux \
> + /sys/kernel/btf/vmlinux \
> + /boot/vmlinux-$(shell uname -r)
> +VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
> +ifeq ($(VMLINUX_BTF),)
> +$(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)")
> +endif
> +
> +ifeq ($(V),1)
> +Q =
> +msg =
> +else
> +Q = @
> +msg = @printf ' %-8s %s%s\n' "$(1)" "$(notdir $(2))" "$(if $(3), $(3))";
> +MAKEFLAGS += --no-print-directory
> +submake_extras := feature_display=0
> +endif
> +
> +.DELETE_ON_ERROR:
> +
> +.PHONY: all clean
> +
> +SOURCES = $(wildcard *.bpf.c)
> +TARGETS = $(SOURCES:.bpf.c=.bpf.o)
> +
> +all: $(TARGETS)
> +
> +clean:
> + $(call msg,CLEAN)
> + $(Q)rm -rf $(OUTPUT) $(TARGETS)
> +
> +%.bpf.o: %.bpf.c vmlinux.h $(BPFOBJ) | $(OUTPUT)
> + $(call msg,BPF,$@)
> + $(Q)$(CLANG) -g -O2 --target=bpf $(INCLUDES) \
> + -c $(filter %.c,$^) -o $@ && \
> + $(LLVM_STRIP) -g $@
> +
> +vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL) | $(INCLUDE_DIR)
> +ifeq ($(VMLINUX_H),)
> + $(call msg,GEN,,$@)
> + $(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
> +else
> + $(call msg,CP,,$@)
> + $(Q)cp "$(VMLINUX_H)" $@
> +endif
> +
> +$(OUTPUT) $(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT):
> + $(call msg,MKDIR,$@)
> + $(Q)mkdir -p $@
> +
> +$(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OUTPUT)
> + $(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC) \
> + OUTPUT=$(abspath $(dir $@))/ prefix= \
> + DESTDIR=$(LIBBPF_DESTDIR) $(abspath $@) install_headers
> +
> +ifeq ($(CROSS_COMPILE),)
> +$(DEFAULT_BPFTOOL): $(BPFOBJ) | $(BPFTOOL_OUTPUT)
> + $(Q)$(MAKE) $(submake_extras) -C $(BPFTOOL_SRC) \
> + OUTPUT=$(BPFTOOL_OUTPUT)/ \
> + LIBBPF_BOOTSTRAP_OUTPUT=$(LIBBPF_OUTPUT)/ \
> + LIBBPF_BOOTSTRAP_DESTDIR=$(LIBBPF_DESTDIR)/ bootstrap
> +else
> +$(DEFAULT_BPFTOOL): | $(BPFTOOL_OUTPUT)
> + $(Q)$(MAKE) $(submake_extras) -C $(BPFTOOL_SRC) \
> + OUTPUT=$(BPFTOOL_OUTPUT)/ bootstrap
> +endif
> diff --git a/drivers/hid/bpf/progs/README b/drivers/hid/bpf/progs/README
> new file mode 100644
> index 000000000000..20b0928f385b
> --- /dev/null
> +++ b/drivers/hid/bpf/progs/README
> @@ -0,0 +1,102 @@
> +# 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
> +```
> diff --git a/drivers/hid/bpf/progs/XPPen__Artist24.bpf.c b/drivers/hid/bpf/progs/XPPen__Artist24.bpf.c
> new file mode 100644
> index 000000000000..e1be6a12bb75
> --- /dev/null
> +++ b/drivers/hid/bpf/progs/XPPen__Artist24.bpf.c
> @@ -0,0 +1,229 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2023 Benjamin Tissoires
> + */
> +
> +#include "vmlinux.h"
> +#include "hid_bpf.h"
> +#include "hid_bpf_helpers.h"
> +#include <bpf/bpf_tracing.h>
> +
> +#define VID_UGEE 0x28BD /* VID is shared with SinoWealth and Glorious and prob others */
> +#define PID_ARTIST_24 0x093A
> +#define PID_ARTIST_24_PRO 0x092D
> +
> +HID_BPF_CONFIG(
> + HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_UGEE, PID_ARTIST_24),
> + HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_UGEE, PID_ARTIST_24_PRO)
> +);
> +
> +/*
> + * We need to amend the report descriptor for the following:
> + * - the device reports Eraser instead of using Secondary Barrel Switch
> + * - the pen doesn't have a rubber tail, so basically we are removing any
> + * eraser/invert bits
> + */
> +static const __u8 fixed_rdesc[] = {
> + 0x05, 0x0d, // Usage Page (Digitizers) 0
> + 0x09, 0x02, // Usage (Pen) 2
> + 0xa1, 0x01, // Collection (Application) 4
> + 0x85, 0x07, // Report ID (7) 6
> + 0x09, 0x20, // Usage (Stylus) 8
> + 0xa1, 0x00, // Collection (Physical) 10
> + 0x09, 0x42, // Usage (Tip Switch) 12
> + 0x09, 0x44, // Usage (Barrel Switch) 14
> + 0x09, 0x5a, // Usage (Secondary Barrel Switch) 16 /* changed from 0x45 (Eraser) to 0x5a (Secondary Barrel Switch) */
> + 0x15, 0x00, // Logical Minimum (0) 18
> + 0x25, 0x01, // Logical Maximum (1) 20
> + 0x75, 0x01, // Report Size (1) 22
> + 0x95, 0x03, // Report Count (3) 24
> + 0x81, 0x02, // Input (Data,Var,Abs) 26
> + 0x95, 0x02, // Report Count (2) 28
> + 0x81, 0x03, // Input (Cnst,Var,Abs) 30
> + 0x09, 0x32, // Usage (In Range) 32
> + 0x95, 0x01, // Report Count (1) 34
> + 0x81, 0x02, // Input (Data,Var,Abs) 36
> + 0x95, 0x02, // Report Count (2) 38
> + 0x81, 0x03, // Input (Cnst,Var,Abs) 40
> + 0x75, 0x10, // Report Size (16) 42
> + 0x95, 0x01, // Report Count (1) 44
> + 0x35, 0x00, // Physical Minimum (0) 46
> + 0xa4, // Push 48
> + 0x05, 0x01, // Usage Page (Generic Desktop) 49
> + 0x09, 0x30, // Usage (X) 51
> + 0x65, 0x13, // Unit (EnglishLinear: in) 53
> + 0x55, 0x0d, // Unit Exponent (-3) 55
> + 0x46, 0xf0, 0x50, // Physical Maximum (20720) 57
> + 0x26, 0xff, 0x7f, // Logical Maximum (32767) 60
> + 0x81, 0x02, // Input (Data,Var,Abs) 63
> + 0x09, 0x31, // Usage (Y) 65
> + 0x46, 0x91, 0x2d, // Physical Maximum (11665) 67
> + 0x26, 0xff, 0x7f, // Logical Maximum (32767) 70
> + 0x81, 0x02, // Input (Data,Var,Abs) 73
> + 0xb4, // Pop 75
> + 0x09, 0x30, // Usage (Tip Pressure) 76
> + 0x45, 0x00, // Physical Maximum (0) 78
> + 0x26, 0xff, 0x1f, // Logical Maximum (8191) 80
> + 0x81, 0x42, // Input (Data,Var,Abs,Null) 83
> + 0x09, 0x3d, // Usage (X Tilt) 85
> + 0x15, 0x81, // Logical Minimum (-127) 87
> + 0x25, 0x7f, // Logical Maximum (127) 89
> + 0x75, 0x08, // Report Size (8) 91
> + 0x95, 0x01, // Report Count (1) 93
> + 0x81, 0x02, // Input (Data,Var,Abs) 95
> + 0x09, 0x3e, // Usage (Y Tilt) 97
> + 0x15, 0x81, // Logical Minimum (-127) 99
> + 0x25, 0x7f, // Logical Maximum (127) 101
> + 0x81, 0x02, // Input (Data,Var,Abs) 103
> + 0xc0, // End Collection 105
> + 0xc0, // End Collection 106
> +};
> +
> +#define BIT(n) (1UL << n)
> +
> +#define TIP_SWITCH BIT(0)
> +#define BARREL_SWITCH BIT(1)
> +#define ERASER BIT(2)
> +/* padding BIT(3) */
> +/* padding BIT(4) */
> +#define IN_RANGE BIT(5)
> +/* padding BIT(6) */
> +/* padding BIT(7) */
> +
> +#define U16(index) (data[index] | (data[index + 1] << 8))
> +
> +SEC("fmod_ret/hid_bpf_rdesc_fixup")
> +int BPF_PROG(hid_fix_rdesc_xppen_artist24, struct hid_bpf_ctx *hctx)
> +{
> + __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 4096 /* size */);
> +
> + if (!data)
> + return 0; /* EPERM check */
> +
> + __builtin_memcpy(data, fixed_rdesc, sizeof(fixed_rdesc));
> +
> + return sizeof(fixed_rdesc);
> +}
> +
> +static __u8 prev_state = 0;
> +
> +/*
> + * There are a few cases where the device is sending wrong event
> + * sequences, all related to the second button (the pen doesn't
> + * have an eraser switch on the tail end):
> + *
> + * whenever the second button gets pressed or released, an
> + * out-of-proximity event is generated and then the firmware
> + * compensate for the missing state (and the firmware uses
> + * eraser for that button):
> + *
> + * - if the pen is in range, an extra out-of-range is sent
> + * when the second button is pressed/released:
> + * // Pen is in range
> + * E: InRange
> + *
> + * // Second button is pressed
> + * E:
> + * E: Eraser InRange
> + *
> + * // Second button is released
> + * E:
> + * E: InRange
> + *
> + * This case is ignored by this filter, it's "valid"
> + * and userspace knows how to deal with it, there are just
> + * a few out-of-prox events generated, but the user doesn´t
> + * see them.
> + *
> + * - if the pen is in contact, 2 extra events are added when
> + * the second button is pressed/released: an out of range
> + * and an in range:
> + *
> + * // Pen is in contact
> + * E: TipSwitch InRange
> + *
> + * // Second button is pressed
> + * E: <- false release, needs to be filtered out
> + * E: Eraser InRange <- false release, needs to be filtered out
> + * E: TipSwitch Eraser InRange
> + *
> + * // Second button is released
> + * E: <- false release, needs to be filtered out
> + * E: InRange <- false release, needs to be filtered out
> + * E: TipSwitch InRange
> + *
> + */
> +SEC("fmod_ret/hid_bpf_device_event")
> +int BPF_PROG(xppen_24_fix_eraser, struct hid_bpf_ctx *hctx)
> +{
> + __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 10 /* size */);
> + __u8 current_state, changed_state;
> + bool prev_tip;
> + __u16 tilt;
> +
> + if (!data)
> + return 0; /* EPERM check */
> +
> + current_state = data[1];
> +
> + /* if the state is identical to previously, early return */
> + if (current_state == prev_state)
> + return 0;
> +
> + prev_tip = !!(prev_state & TIP_SWITCH);
> +
> + /*
> + * Illegal transition: pen is in range with the tip pressed, and
> + * it goes into out of proximity.
> + *
> + * Ideally we should hold the event, start a timer and deliver it
> + * only if the timer ends, but we are not capable of that now.
> + *
> + * And it doesn't matter because when we are in such cases, this
> + * means we are detecting a false release.
> + */
> + if ((current_state & IN_RANGE) == 0) {
> + if (prev_tip)
> + return HID_IGNORE_EVENT;
> + return 0;
> + }
> +
> + /*
> + * XOR to only set the bits that have changed between
> + * previous and current state
> + */
> + changed_state = prev_state ^ current_state;
> +
> + /* Store the new state for future processing */
> + prev_state = current_state;
> +
> + /*
> + * We get both a tipswitch and eraser change in the same HID report:
> + * this is not an authorized transition and is unlikely to happen
> + * in real life.
> + * This is likely to be added by the firmware to emulate the
> + * eraser mode so we can skip the event.
> + */
> + if ((changed_state & (TIP_SWITCH | ERASER)) == (TIP_SWITCH | ERASER)) /* we get both a tipswitch and eraser change at the same time */
> + return HID_IGNORE_EVENT;
> +
> + return 0;
> +}
> +
> +SEC("syscall")
> +int probe(struct hid_bpf_probe_args *ctx)
> +{
> + /*
> + * The device exports 3 interfaces.
> + */
> + ctx->retval = ctx->rdesc_size != 107;
> + if (ctx->retval)
> + ctx->retval = -EINVAL;
> +
> + /* ensure the kernel isn't fixed already */
> + if (ctx->rdesc[17] != 0x45) /* Eraser */
> + ctx->retval = -EINVAL;
> +
> + return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> diff --git a/drivers/hid/bpf/progs/hid_bpf.h b/drivers/hid/bpf/progs/hid_bpf.h
> new file mode 100644
> index 000000000000..7ee371cac2e1
> --- /dev/null
> +++ b/drivers/hid/bpf/progs/hid_bpf.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/* Copyright (c) 2022 Benjamin Tissoires
> + */
> +
> +#ifndef ____HID_BPF__H
> +#define ____HID_BPF__H
> +
> +struct hid_bpf_probe_args {
> + unsigned int hid;
> + unsigned int rdesc_size;
> + unsigned char rdesc[4096];
> + int retval;
> +};
> +
> +#endif /* ____HID_BPF__H */
> diff --git a/drivers/hid/bpf/progs/hid_bpf_helpers.h b/drivers/hid/bpf/progs/hid_bpf_helpers.h
> new file mode 100644
> index 000000000000..1d53b10aaa2e
> --- /dev/null
> +++ b/drivers/hid/bpf/progs/hid_bpf_helpers.h
> @@ -0,0 +1,170 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/* Copyright (c) 2022 Benjamin Tissoires
> + */
> +
> +#ifndef __HID_BPF_HELPERS_H
> +#define __HID_BPF_HELPERS_H
> +
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <linux/errno.h>
> +
> +extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx,
> + unsigned int offset,
> + const size_t __sz) __ksym;
> +extern struct hid_bpf_ctx *hid_bpf_allocate_context(unsigned int hid_id) __ksym;
> +extern void hid_bpf_release_context(struct hid_bpf_ctx *ctx) __ksym;
> +extern int hid_bpf_hw_request(struct hid_bpf_ctx *ctx,
> + __u8 *data,
> + size_t buf__sz,
> + enum hid_report_type type,
> + enum hid_class_request reqtype) __ksym;
> +
> +#define HID_MAX_DESCRIPTOR_SIZE 4096
> +#define HID_IGNORE_EVENT -1
> +
> +/* extracted from <linux/input.h> */
> +#define BUS_ANY 0x00
> +#define BUS_PCI 0x01
> +#define BUS_ISAPNP 0x02
> +#define BUS_USB 0x03
> +#define BUS_HIL 0x04
> +#define BUS_BLUETOOTH 0x05
> +#define BUS_VIRTUAL 0x06
> +#define BUS_ISA 0x10
> +#define BUS_I8042 0x11
> +#define BUS_XTKBD 0x12
> +#define BUS_RS232 0x13
> +#define BUS_GAMEPORT 0x14
> +#define BUS_PARPORT 0x15
> +#define BUS_AMIGA 0x16
> +#define BUS_ADB 0x17
> +#define BUS_I2C 0x18
> +#define BUS_HOST 0x19
> +#define BUS_GSC 0x1A
> +#define BUS_ATARI 0x1B
> +#define BUS_SPI 0x1C
> +#define BUS_RMI 0x1D
> +#define BUS_CEC 0x1E
> +#define BUS_INTEL_ISHTP 0x1F
> +#define BUS_AMD_SFH 0x20
> +
> +/* extracted from <linux/hid.h> */
> +#define HID_GROUP_ANY 0x0000
> +#define HID_GROUP_GENERIC 0x0001
> +#define HID_GROUP_MULTITOUCH 0x0002
> +#define HID_GROUP_SENSOR_HUB 0x0003
> +#define HID_GROUP_MULTITOUCH_WIN_8 0x0004
> +#define HID_GROUP_RMI 0x0100
> +#define HID_GROUP_WACOM 0x0101
> +#define HID_GROUP_LOGITECH_DJ_DEVICE 0x0102
> +#define HID_GROUP_STEAM 0x0103
> +#define HID_GROUP_LOGITECH_27MHZ_DEVICE 0x0104
> +#define HID_GROUP_VIVALDI 0x0105
> +
> +/* include/linux/mod_devicetable.h defines as (~0), but that gives us negative size arrays */
> +#define HID_VID_ANY 0x0000
> +#define HID_PID_ANY 0x0000
> +
> +/* duplicated from incluse/linux/array_size.h
> + */
FWIW, Peter mentioned on the matching MR on udev-hid-bpf that this
comment was likely superflous:
https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/66#note_2365932
Cheers,
Benjamin
> +#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
> +
> +/* Helper macro to convert (foo, __LINE__) into foo134 so we can use __LINE__ for
> + * field/variable names
> + */
> +#define COMBINE1(X, Y) X ## Y
> +#define COMBINE(X, Y) COMBINE1(X, Y)
> +
> +/* Macro magic:
> + * __uint(foo, 123) creates a int (*foo)[1234]
> + *
> + * We use that macro to declare an anonymous struct with several
> + * fields, each is the declaration of an pointer to an array of size
> + * bus/group/vid/pid. (Because it's a pointer to such an array, actual storage
> + * would be sizeof(pointer) rather than sizeof(array). Not that we ever
> + * instantiate it anyway).
> + *
> + * This is only used for BTF introspection, we can later check "what size
> + * is the bus array" in the introspection data and thus extract the bus ID
> + * again.
> + *
> + * And we use the __LINE__ to give each of our structs a unique name so the
> + * BPF program writer doesn't have to.
> + *
> + * $ bpftool btf dump file target/bpf/HP_Elite_Presenter.bpf.o
> + * shows the inspection data, start by searching for .hid_bpf_config
> + * and working backwards from that (each entry references the type_id of the
> + * content).
> + */
> +
> +#define HID_DEVICE(b, g, ven, prod) \
> + struct { \
> + __uint(name, 0); \
> + __uint(bus, (b)); \
> + __uint(group, (g)); \
> + __uint(vid, (ven)); \
> + __uint(pid, (prod)); \
> + } COMBINE(_entry, __LINE__)
> +
> +/* Macro magic below is to make HID_BPF_CONFIG() look like a function call that
> + * we can pass multiple HID_DEVICE() invocations in.
> + *
> + * For up to 16 arguments, HID_BPF_CONFIG(one, two) resolves to
> + *
> + * union {
> + * HID_DEVICE(...);
> + * HID_DEVICE(...);
> + * } _device_ids SEC(".hid_bpf_config")
> + *
> + */
> +
> +/* Returns the number of macro arguments, this expands
> + * NARGS(a, b, c) to NTH_ARG(a, b, c, 15, 14, 13, .... 4, 3, 2, 1).
> + * NTH_ARG always returns the 16th argument which in our case is 3.
> + *
> + * If we want more than 16 values _COUNTDOWN and _NTH_ARG both need to be
> + * updated.
> + */
> +#define _NARGS(...) _NARGS1(__VA_ARGS__, _COUNTDOWN)
> +#define _NARGS1(...) _NTH_ARG(__VA_ARGS__)
> +
> +/* Add to this if we need more than 16 args */
> +#define _COUNTDOWN \
> + 15, 14, 13, 12, 11, 10, 9, 8, \
> + 7, 6, 5, 4, 3, 2, 1, 0
> +
> +/* Return the 16 argument passed in. See _NARGS above for usage. Note this is
> + * 1-indexed.
> + */
> +#define _NTH_ARG( \
> + _1, _2, _3, _4, _5, _6, _7, _8, \
> + _9, _10, _11, _12, _13, _14, _15,\
> + N, ...) N
> +
> +/* Turns EXPAND(_ARG, a, b, c) into _ARG3(a, b, c) */
> +#define _EXPAND(func, ...) COMBINE(func, _NARGS(__VA_ARGS__)) (__VA_ARGS__)
> +
> +/* And now define all the ARG macros for each number of args we want to accept */
> +#define _ARG1(_1) _1;
> +#define _ARG2(_1, _2) _1; _2;
> +#define _ARG3(_1, _2, _3) _1; _2; _3;
> +#define _ARG4(_1, _2, _3, _4) _1; _2; _3; _4;
> +#define _ARG5(_1, _2, _3, _4, _5) _1; _2; _3; _4; _5;
> +#define _ARG6(_1, _2, _3, _4, _5, _6) _1; _2; _3; _4; _5; _6;
> +#define _ARG7(_1, _2, _3, _4, _5, _6, _7) _1; _2; _3; _4; _5; _6; _7;
> +#define _ARG8(_1, _2, _3, _4, _5, _6, _7, _8) _1; _2; _3; _4; _5; _6; _7; _8;
> +#define _ARG9(_1, _2, _3, _4, _5, _6, _7, _8, _9) _1; _2; _3; _4; _5; _6; _7; _8; _9;
> +#define _ARG10(_1, _2, _3, _4, _5, _6, _7, _8, _9, _a) _1; _2; _3; _4; _5; _6; _7; _8; _9; _a;
> +#define _ARG11(_1, _2, _3, _4, _5, _6, _7, _8, _9, _a, _b) _1; _2; _3; _4; _5; _6; _7; _8; _9; _a; _b;
> +#define _ARG12(_1, _2, _3, _4, _5, _6, _7, _8, _9, _a, _b, _c) _1; _2; _3; _4; _5; _6; _7; _8; _9; _a; _b; _c;
> +#define _ARG13(_1, _2, _3, _4, _5, _6, _7, _8, _9, _a, _b, _c, _d) _1; _2; _3; _4; _5; _6; _7; _8; _9; _a; _b; _c; _d;
> +#define _ARG14(_1, _2, _3, _4, _5, _6, _7, _8, _9, _a, _b, _c, _d, _e) _1; _2; _3; _4; _5; _6; _7; _8; _9; _a; _b; _c; _d; _e;
> +#define _ARG15(_1, _2, _3, _4, _5, _6, _7, _8, _9, _a, _b, _c, _d, _e, _f) _1; _2; _3; _4; _5; _6; _7; _8; _9; _a; _b; _c; _d; _e; _f;
> +
> +
> +#define HID_BPF_CONFIG(...) union { \
> + _EXPAND(_ARG, __VA_ARGS__) \
> +} _device_ids SEC(".hid_bpf_config")
> +
> +#endif /* __HID_BPF_HELPERS_H */
>
> --
> 2.44.0
>