Author | Tokens | Token Proportion | Commits | Commit Proportion |
---|---|---|---|---|
Benjamin Tissoires | 583 | 100.00% | 3 | 100.00% |
Total | 583 | 3 |
// SPDX-License-Identifier: GPL-2.0-only /* Copyright (c) 2024 Benjamin Tissoires */ #include "vmlinux.h" #include "hid_bpf.h" #include "hid_bpf_helpers.h" #include <bpf/bpf_tracing.h> #define VID_WACOM 0x056a #define ART_PEN_ID 0x0804 #define PID_INTUOS_PRO_2_M 0x0357 HID_BPF_CONFIG( HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_WACOM, PID_INTUOS_PRO_2_M) ); /* * This filter is here for the Art Pen stylus only: * - when used on some Wacom devices (see the list of attached PIDs), this pen * reports pressure every other events. * - to solve that, given that we know that the next event will be the same as * the current one, we can emulate a smoother pressure reporting by reporting * the mean of the previous value and the current one. * * We are effectively delaying the pressure by one event every other event, but * that's less of an annoyance compared to the chunkiness of the reported data. * * For example, let's assume the following set of events: * <Tip switch 0> <X 0> <Y 0> <Pressure 0 > <Tooltype 0x0804> * <Tip switch 1> <X 1> <Y 1> <Pressure 100 > <Tooltype 0x0804> * <Tip switch 1> <X 2> <Y 2> <Pressure 100 > <Tooltype 0x0804> * <Tip switch 1> <X 3> <Y 3> <Pressure 200 > <Tooltype 0x0804> * <Tip switch 1> <X 4> <Y 4> <Pressure 200 > <Tooltype 0x0804> * <Tip switch 0> <X 5> <Y 5> <Pressure 0 > <Tooltype 0x0804> * * The filter will report: * <Tip switch 0> <X 0> <Y 0> <Pressure 0 > <Tooltype 0x0804> * <Tip switch 1> <X 1> <Y 1> <Pressure * 50*> <Tooltype 0x0804> * <Tip switch 1> <X 2> <Y 2> <Pressure 100 > <Tooltype 0x0804> * <Tip switch 1> <X 3> <Y 3> <Pressure *150*> <Tooltype 0x0804> * <Tip switch 1> <X 4> <Y 4> <Pressure 200 > <Tooltype 0x0804> * <Tip switch 0> <X 5> <Y 5> <Pressure 0 > <Tooltype 0x0804> * */ struct wacom_params { __u16 pid; __u16 rdesc_len; __u8 report_id; __u8 report_len; struct { __u8 tip_switch; __u8 pressure; __u8 tool_type; } offsets; }; /* * Multiple device can support the same stylus, so * we need to know which device has which offsets */ static const struct wacom_params devices[] = { { .pid = PID_INTUOS_PRO_2_M, .rdesc_len = 949, .report_id = 16, .report_len = 27, .offsets = { .tip_switch = 1, .pressure = 8, .tool_type = 25, }, }, }; static struct wacom_params params = { 0 }; /* HID-BPF reports a 64 bytes chunk anyway, so this ensures * the verifier to know we are addressing the memory correctly */ #define PEN_REPORT_LEN 64 /* only odd frames are modified */ static bool odd; static __u16 prev_pressure; static inline void *get_bits(__u8 *data, unsigned int byte_offset) { return data + byte_offset; } static inline __u16 *get_u16(__u8 *data, unsigned int offset) { return (__u16 *)get_bits(data, offset); } static inline __u8 *get_u8(__u8 *data, unsigned int offset) { return (__u8 *)get_bits(data, offset); } SEC(HID_BPF_DEVICE_EVENT) int BPF_PROG(artpen_pressure_interpolate, struct hid_bpf_ctx *hctx) { __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, PEN_REPORT_LEN /* size */); __u16 *pressure, *tool_type; __u8 *tip_switch; if (!data) return 0; /* EPERM check */ if (data[0] != params.report_id || params.offsets.tip_switch >= PEN_REPORT_LEN || params.offsets.pressure >= PEN_REPORT_LEN - 1 || params.offsets.tool_type >= PEN_REPORT_LEN - 1) return 0; /* invalid report or parameters */ tool_type = get_u16(data, params.offsets.tool_type); if (*tool_type != ART_PEN_ID) return 0; tip_switch = get_u8(data, params.offsets.tip_switch); if ((*tip_switch & 0x01) == 0) { prev_pressure = 0; odd = true; return 0; } pressure = get_u16(data, params.offsets.pressure); if (odd) *pressure = (*pressure + prev_pressure) / 2; prev_pressure = *pressure; odd = !odd; return 0; } HID_BPF_OPS(wacom_artpen) = { .hid_device_event = (void *)artpen_pressure_interpolate, }; SEC("syscall") int probe(struct hid_bpf_probe_args *ctx) { struct hid_bpf_ctx *hid_ctx; __u16 pid; int i; /* get a struct hid_device to access the actual pid of the device */ hid_ctx = hid_bpf_allocate_context(ctx->hid); if (!hid_ctx) { ctx->retval = -ENODEV; return -1; /* EPERM check */ } pid = hid_ctx->hid->product; ctx->retval = -EINVAL; /* Match the given device with the list of known devices */ for (i = 0; i < ARRAY_SIZE(devices); i++) { const struct wacom_params *device = &devices[i]; if (device->pid == pid && device->rdesc_len == ctx->rdesc_size) { params = *device; ctx->retval = 0; } } hid_bpf_release_context(hid_ctx); return 0; } char _license[] SEC("license") = "GPL";
Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.
Created with Cregit http://github.com/cregit/cregit
Version 2.0-RC1