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// 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_HUION 0x256C
#define PID_KAMVAS_PRO_19 0x006B
#define NAME_KAMVAS_PRO_19 "HUION Huion Tablet_GT1902"
#define TEST_PREFIX "uhid test "
HID_BPF_CONFIG(
HID_DEVICE(BUS_USB, HID_GROUP_MULTITOUCH_WIN_8, VID_HUION, PID_KAMVAS_PRO_19),
);
bool prev_was_out_of_range;
bool in_eraser_mode;
/*
* We need to amend the report descriptor for the following:
* - the second button is reported through Secondary Tip Switch instead of Secondary Barrel Switch
* - the third button is reported through Invert, and we need some room to report it.
*
*/
static const __u8 fixed_rdesc[] = {
0x05, 0x0d, // Usage Page (Digitizers) 0
0x09, 0x02, // Usage (Pen) 2
0xa1, 0x01, // Collection (Application) 4
0x85, 0x0a, // Report ID (10) 6
0x09, 0x20, // Usage (Stylus) 8
0xa1, 0x01, // Collection (Application) 10
0x09, 0x42, // Usage (Tip Switch) 12
0x09, 0x44, // Usage (Barrel Switch) 14
0x09, 0x5a, // Usage (Secondary Barrel Switch) 16 /* changed from Secondary Tip Switch */
0x09, 0x3c, // Usage (Invert) 18
0x09, 0x45, // Usage (Eraser) 20
0x15, 0x00, // Logical Minimum (0) 22
0x25, 0x01, // Logical Maximum (1) 24
0x75, 0x01, // Report Size (1) 26
0x95, 0x05, // Report Count (5) 28 /* changed (was 5) */
0x81, 0x02, // Input (Data,Var,Abs) 30
0x05, 0x09, // Usage Page (Button) /* inserted */
0x09, 0x4a, // Usage (0x4a) /* inserted to be translated as input usage 0x149: BTN_STYLUS3 */
0x95, 0x01, // Report Count (1) /* inserted */
0x81, 0x02, // Input (Data,Var,Abs) /* inserted */
0x05, 0x0d, // Usage Page (Digitizers) /* inserted */
0x09, 0x32, // Usage (In Range) 32
0x75, 0x01, // Report Size (1) 34
0x95, 0x01, // Report Count (1) 36
0x81, 0x02, // Input (Data,Var,Abs) 38
0x81, 0x03, // Input (Cnst,Var,Abs) 40
0x05, 0x01, // Usage Page (Generic Desktop) 42
0x09, 0x30, // Usage (X) 44
0x09, 0x31, // Usage (Y) 46
0x55, 0x0d, // Unit Exponent (-3) 48
0x65, 0x33, // Unit (EnglishLinear: in³) 50
0x26, 0xff, 0x7f, // Logical Maximum (32767) 52
0x35, 0x00, // Physical Minimum (0) 55
0x46, 0x00, 0x08, // Physical Maximum (2048) 57
0x75, 0x10, // Report Size (16) 60
0x95, 0x02, // Report Count (2) 62
0x81, 0x02, // Input (Data,Var,Abs) 64
0x05, 0x0d, // Usage Page (Digitizers) 66
0x09, 0x30, // Usage (Tip Pressure) 68
0x26, 0xff, 0x3f, // Logical Maximum (16383) 70
0x75, 0x10, // Report Size (16) 73
0x95, 0x01, // Report Count (1) 75
0x81, 0x02, // Input (Data,Var,Abs) 77
0x09, 0x3d, // Usage (X Tilt) 79
0x09, 0x3e, // Usage (Y Tilt) 81
0x15, 0xa6, // Logical Minimum (-90) 83
0x25, 0x5a, // Logical Maximum (90) 85
0x75, 0x08, // Report Size (8) 87
0x95, 0x02, // Report Count (2) 89
0x81, 0x02, // Input (Data,Var,Abs) 91
0xc0, // End Collection 93
0xc0, // End Collection 94
0x05, 0x0d, // Usage Page (Digitizers) 95
0x09, 0x04, // Usage (Touch Screen) 97
0xa1, 0x01, // Collection (Application) 99
0x85, 0x04, // Report ID (4) 101
0x09, 0x22, // Usage (Finger) 103
0xa1, 0x02, // Collection (Logical) 105
0x05, 0x0d, // Usage Page (Digitizers) 107
0x95, 0x01, // Report Count (1) 109
0x75, 0x06, // Report Size (6) 111
0x09, 0x51, // Usage (Contact Id) 113
0x15, 0x00, // Logical Minimum (0) 115
0x25, 0x3f, // Logical Maximum (63) 117
0x81, 0x02, // Input (Data,Var,Abs) 119
0x09, 0x42, // Usage (Tip Switch) 121
0x25, 0x01, // Logical Maximum (1) 123
0x75, 0x01, // Report Size (1) 125
0x95, 0x01, // Report Count (1) 127
0x81, 0x02, // Input (Data,Var,Abs) 129
0x75, 0x01, // Report Size (1) 131
0x95, 0x01, // Report Count (1) 133
0x81, 0x03, // Input (Cnst,Var,Abs) 135
0x05, 0x01, // Usage Page (Generic Desktop) 137
0x75, 0x10, // Report Size (16) 139
0x55, 0x0e, // Unit Exponent (-2) 141
0x65, 0x11, // Unit (SILinear: cm) 143
0x09, 0x30, // Usage (X) 145
0x26, 0xff, 0x7f, // Logical Maximum (32767) 147
0x35, 0x00, // Physical Minimum (0) 150
0x46, 0x15, 0x0c, // Physical Maximum (3093) 152
0x81, 0x42, // Input (Data,Var,Abs,Null) 155
0x09, 0x31, // Usage (Y) 157
0x26, 0xff, 0x7f, // Logical Maximum (32767) 159
0x46, 0xcb, 0x06, // Physical Maximum (1739) 162
0x81, 0x42, // Input (Data,Var,Abs,Null) 165
0x05, 0x0d, // Usage Page (Digitizers) 167
0x09, 0x30, // Usage (Tip Pressure) 169
0x26, 0xff, 0x1f, // Logical Maximum (8191) 171
0x75, 0x10, // Report Size (16) 174
0x95, 0x01, // Report Count (1) 176
0x81, 0x02, // Input (Data,Var,Abs) 178
0xc0, // End Collection 180
0x05, 0x0d, // Usage Page (Digitizers) 181
0x09, 0x22, // Usage (Finger) 183
0xa1, 0x02, // Collection (Logical) 185
0x05, 0x0d, // Usage Page (Digitizers) 187
0x95, 0x01, // Report Count (1) 189
0x75, 0x06, // Report Size (6) 191
0x09, 0x51, // Usage (Contact Id) 193
0x15, 0x00, // Logical Minimum (0) 195
0x25, 0x3f, // Logical Maximum (63) 197
0x81, 0x02, // Input (Data,Var,Abs) 199
0x09, 0x42, // Usage (Tip Switch) 201
0x25, 0x01, // Logical Maximum (1) 203
0x75, 0x01, // Report Size (1) 205
0x95, 0x01, // Report Count (1) 207
0x81, 0x02, // Input (Data,Var,Abs) 209
0x75, 0x01, // Report Size (1) 211
0x95, 0x01, // Report Count (1) 213
0x81, 0x03, // Input (Cnst,Var,Abs) 215
0x05, 0x01, // Usage Page (Generic Desktop) 217
0x75, 0x10, // Report Size (16) 219
0x55, 0x0e, // Unit Exponent (-2) 221
0x65, 0x11, // Unit (SILinear: cm) 223
0x09, 0x30, // Usage (X) 225
0x26, 0xff, 0x7f, // Logical Maximum (32767) 227
0x35, 0x00, // Physical Minimum (0) 230
0x46, 0x15, 0x0c, // Physical Maximum (3093) 232
0x81, 0x42, // Input (Data,Var,Abs,Null) 235
0x09, 0x31, // Usage (Y) 237
0x26, 0xff, 0x7f, // Logical Maximum (32767) 239
0x46, 0xcb, 0x06, // Physical Maximum (1739) 242
0x81, 0x42, // Input (Data,Var,Abs,Null) 245
0x05, 0x0d, // Usage Page (Digitizers) 247
0x09, 0x30, // Usage (Tip Pressure) 249
0x26, 0xff, 0x1f, // Logical Maximum (8191) 251
0x75, 0x10, // Report Size (16) 254
0x95, 0x01, // Report Count (1) 256
0x81, 0x02, // Input (Data,Var,Abs) 258
0xc0, // End Collection 260
0x05, 0x0d, // Usage Page (Digitizers) 261
0x09, 0x56, // Usage (Scan Time) 263
0x55, 0x00, // Unit Exponent (0) 265
0x65, 0x00, // Unit (None) 267
0x27, 0xff, 0xff, 0xff, 0x7f, // Logical Maximum (2147483647) 269
0x95, 0x01, // Report Count (1) 274
0x75, 0x20, // Report Size (32) 276
0x81, 0x02, // Input (Data,Var,Abs) 278
0x09, 0x54, // Usage (Contact Count) 280
0x25, 0x7f, // Logical Maximum (127) 282
0x95, 0x01, // Report Count (1) 284
0x75, 0x08, // Report Size (8) 286
0x81, 0x02, // Input (Data,Var,Abs) 288
0x75, 0x08, // Report Size (8) 290
0x95, 0x08, // Report Count (8) 292
0x81, 0x03, // Input (Cnst,Var,Abs) 294
0x85, 0x05, // Report ID (5) 296
0x09, 0x55, // Usage (Contact Max) 298
0x25, 0x0a, // Logical Maximum (10) 300
0x75, 0x08, // Report Size (8) 302
0x95, 0x01, // Report Count (1) 304
0xb1, 0x02, // Feature (Data,Var,Abs) 306
0x06, 0x00, 0xff, // Usage Page (Vendor Defined Page 1) 308
0x09, 0xc5, // Usage (Vendor Usage 0xc5) 311
0x85, 0x06, // Report ID (6) 313
0x15, 0x00, // Logical Minimum (0) 315
0x26, 0xff, 0x00, // Logical Maximum (255) 317
0x75, 0x08, // Report Size (8) 320
0x96, 0x00, 0x01, // Report Count (256) 322
0xb1, 0x02, // Feature (Data,Var,Abs) 325
0xc0, // End Collection 327
};
SEC("fmod_ret/hid_bpf_rdesc_fixup")
int BPF_PROG(hid_fix_rdesc_huion_kamvas_pro_19, struct hid_bpf_ctx *hctx)
{
__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, HID_MAX_DESCRIPTOR_SIZE /* size */);
if (!data)
return 0; /* EPERM check */
__builtin_memcpy(data, fixed_rdesc, sizeof(fixed_rdesc));
return sizeof(fixed_rdesc);
}
/*
* This tablet reports the 3rd button through invert, but this conflict
* with the normal eraser mode.
* Fortunately, before entering eraser mode, (so Invert = 1),
* the tablet always sends an out-of-proximity event.
* So we can detect that single event and:
* - if there was none but the invert bit was toggled: this is the
* third button
* - if there was this out-of-proximity event, we are entering
* eraser mode, and we will until the next out-of-proximity.
*/
SEC("fmod_ret/hid_bpf_device_event")
int BPF_PROG(kamvas_pro_19_fix_3rd_button, struct hid_bpf_ctx *hctx)
{
__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 10 /* size */);
if (!data)
return 0; /* EPERM check */
if (data[0] != 0x0a) /* not the pen report ID */
return 0;
/* stylus is out of range */
if (!(data[1] & 0x40)) {
prev_was_out_of_range = true;
in_eraser_mode = false;
return 0;
}
/* going into eraser mode (Invert = 1) only happens after an
* out of range event
*/
if (prev_was_out_of_range && (data[1] & 0x18))
in_eraser_mode = true;
/* eraser mode works fine */
if (in_eraser_mode)
return 0;
/* copy the Invert bit reported for the 3rd button in bit 7 */
if (data[1] & 0x08)
data[1] |= 0x20;
/* clear Invert bit now that it was copied */
data[1] &= 0xf7;
prev_was_out_of_range = false;
return 0;
}
SEC("syscall")
int probe(struct hid_bpf_probe_args *ctx)
{
ctx->retval = ctx->rdesc_size != 328;
if (ctx->retval)
ctx->retval = -EINVAL;
/* ensure the kernel isn't fixed already */
if (ctx->rdesc[17] != 0x43) /* Secondary Tip Switch */
ctx->retval = -EINVAL;
struct hid_bpf_ctx *hctx = hid_bpf_allocate_context(ctx->hid);
if (!hctx) {
return ctx->retval = -EINVAL;
return 0;
}
const char *name = hctx->hid->name;
/* strip out TEST_PREFIX */
if (!__builtin_memcmp(name, TEST_PREFIX, sizeof(TEST_PREFIX) - 1))
name += sizeof(TEST_PREFIX) - 1;
if (__builtin_memcmp(name, NAME_KAMVAS_PRO_19, sizeof(NAME_KAMVAS_PRO_19)))
ctx->retval = -EINVAL;
hid_bpf_release_context(hctx);
return 0;
}
char _license[] SEC("license") = "GPL";
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