1 // SPDX-License-Identifier: GPL-2.0-only 2 #include "vmlinux.h" 3 #include "hid_bpf.h" 4 #include "hid_bpf_helpers.h" 5 #include <bpf/bpf_tracing.h> 6 7 /* 8 * Huion Inspiroy Frego M Pen Tablet 9 * Model L610 10 * 256c:8251 (Bluetooth) 11 * 256c:2012 (USB) 12 */ 13 #define VID_HUION 0x256C 14 #define PID_INSPIROY_FREGO_M 0x8251 15 #define PID_L610 0x2012 16 17 #define PEN_RDESC_SIZE 125 18 #define SECONDARY_SWITCH_OFFSET 17 19 20 HID_BPF_CONFIG( 21 HID_DEVICE(BUS_BLUETOOTH, HID_GROUP_GENERIC, VID_HUION, PID_INSPIROY_FREGO_M), 22 HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_HUION, PID_L610) 23 ); 24 25 /* 26 * The pen descriptor reports the second side button as Secondary Tip Switch 27 * instead of Secondary Barrel Switch. 28 * 29 * Relevant part of the original pen report descriptor: 30 * 31 * 0x09, 0x42, // Usage (Tip Switch) 12 32 * 0x09, 0x44, // Usage (Barrel Switch) 14 33 * 0x09, 0x43, // Usage (Secondary Tip Switch) 16 <- change to 0x5a 34 * 0x09, 0x3c, // Usage (Invert) 18 35 * 0x09, 0x45, // Usage (Eraser) 20 36 * 0x15, 0x00, // Logical Minimum (0) 22 37 * 0x25, 0x01, // Logical Maximum (1) 24 38 */ 39 SEC(HID_BPF_RDESC_FIXUP) 40 int BPF_PROG(fix_secondary_barrel_rdesc, struct hid_bpf_ctx *hctx) 41 { 42 __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, HID_MAX_DESCRIPTOR_SIZE /* size */); 43 44 if (!data) 45 return 0; /* EPERM check */ 46 47 if (hctx->size != PEN_RDESC_SIZE) 48 return 0; 49 50 if (data[0] != 0x05 || data[1] != 0x0d || /* Usage Page (Digitizers) */ 51 data[2] != 0x09 || data[3] != 0x02 || /* Usage (Pen) */ 52 data[16] != 0x09 || 53 data[SECONDARY_SWITCH_OFFSET] != 0x43) /* Secondary Tip Switch */ 54 return 0; 55 56 data[SECONDARY_SWITCH_OFFSET] = 0x5a; 57 58 return 0; 59 } 60 61 HID_BPF_OPS(fix_secondary_barrel) = { 62 .hid_rdesc_fixup = (void *)fix_secondary_barrel_rdesc, 63 }; 64 65 SEC("syscall") 66 int probe(struct hid_bpf_probe_args *ctx) 67 { 68 ctx->retval = ctx->rdesc_size != PEN_RDESC_SIZE; 69 if (ctx->retval) { 70 ctx->retval = -EINVAL; 71 return 0; 72 } 73 74 if (ctx->rdesc[0] != 0x05 || ctx->rdesc[1] != 0x0d || /* Usage Page (Digitizers) */ 75 ctx->rdesc[2] != 0x09 || ctx->rdesc[3] != 0x02 || /* Usage (Pen) */ 76 ctx->rdesc[16] != 0x09 || 77 ctx->rdesc[SECONDARY_SWITCH_OFFSET] != 0x43) { /* Secondary Tip Switch */ 78 ctx->retval = -EINVAL; 79 return 0; 80 } 81 82 ctx->retval = 0; 83 84 return 0; 85 } 86 87 char _license[] SEC("license") = "GPL"; 88