1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Copyright (c) 2024 Red Hat, Inc
3 */
4
5 #include "vmlinux.h"
6 #include "hid_bpf.h"
7 #include "hid_bpf_helpers.h"
8 #include "hid_report_helpers.h"
9 #include <bpf/bpf_tracing.h>
10
11 #define VID_HUION 0x256C
12 #define PID_KEYDIAL_K20 0x0069
13
14 HID_BPF_CONFIG(
15 HID_DEVICE(BUS_USB, HID_GROUP_GENERIC, VID_HUION, PID_KEYDIAL_K20),
16 );
17
18 /* Filled in by udev-hid-bpf */
19 char UDEV_PROP_HUION_FIRMWARE_ID[64];
20
21 /* The prefix of the firmware ID we expect for this device. The full firmware
22 * string has a date suffix, e.g. HUION_T21h_230511
23 */
24 char EXPECTED_FIRMWARE_ID[] = "HUION_T21h_";
25
26 /* How this BPF program works: the tablet has two modes, firmware mode and
27 * tablet mode. In firmware mode (out of the box) the tablet sends button events
28 * as keyboard shortcuts and the dial as wheel but it's not forwarded by the kernel.
29 * In tablet mode it uses a vendor specific hid report to report everything instead.
30 * Depending on the mode some hid reports are never sent and the corresponding
31 * devices are mute.
32 *
33 * To switch the tablet use e.g. https://github.com/whot/huion-switcher
34 * or one of the tools from the digimend project
35 *
36 * This BPF currently works for both modes only. The huion-switcher tool sets the
37 * HUION_FIRMWARE_ID udev property - if that is set then we disable the firmware
38 * pad and pen reports (by making them vendor collections that are ignored).
39 * If that property is not set we fix all hidraw nodes so the tablet works in
40 * either mode though the drawback is that the device will show up twice if
41 * you bind it to all event nodes
42 *
43 * Default report descriptor for the first exposed hidraw node:
44 *
45 * # HUION Huion Keydial_K20
46 * # Report descriptor length: 18 bytes
47 * # 0x06, 0x00, 0xff, // Usage Page (Vendor Defined Page 0xFF00) 0
48 * # 0x09, 0x01, // Usage (Vendor Usage 0x01) 3
49 * # 0xa1, 0x01, // Collection (Application) 5
50 * # 0x85, 0x08, // Report ID (8) 7
51 * # 0x75, 0x58, // Report Size (88) 9
52 * # 0x95, 0x01, // Report Count (1) 11
53 * # 0x09, 0x01, // Usage (Vendor Usage 0x01) 13
54 * # 0x81, 0x02, // Input (Data,Var,Abs) 15
55 * # 0xc0, // End Collection 17
56 * R: 18 06 00 ff 09 01 a1 01 85 08 75 58 95 01 09 01 81 02 c0
57 *
58 * This report descriptor appears to be identical for all Huion devices.
59 *
60 * Second hidraw node is the Pad. This one sends the button events until the tablet is
61 * switched to raw mode, then it's mute.
62 *
63 * # HUION Huion Keydial_K20
64 * # Report descriptor length: 135 bytes
65 * # 0x05, 0x01, // Usage Page (Generic Desktop) 0
66 * # 0x09, 0x06, // Usage (Keyboard) 2
67 * # 0xa1, 0x01, // Collection (Application) 4
68 * # 0x85, 0x03, // Report ID (3) 6
69 * # 0x05, 0x07, // Usage Page (Keyboard/Keypad) 8
70 * # 0x19, 0xe0, // UsageMinimum (224) 10
71 * # 0x29, 0xe7, // UsageMaximum (231) 12
72 * # 0x15, 0x00, // Logical Minimum (0) 14
73 * # 0x25, 0x01, // Logical Maximum (1) 16
74 * # 0x75, 0x01, // Report Size (1) 18
75 * # 0x95, 0x08, // Report Count (8) 20
76 * # 0x81, 0x02, // Input (Data,Var,Abs) 22
77 * # 0x05, 0x07, // Usage Page (Keyboard/Keypad) 24
78 * # 0x19, 0x00, // UsageMinimum (0) 26
79 * # 0x29, 0xff, // UsageMaximum (255) 28
80 * # 0x26, 0xff, 0x00, // Logical Maximum (255) 30
81 * # 0x75, 0x08, // Report Size (8) 33
82 * # 0x95, 0x06, // Report Count (6) 35
83 * # 0x81, 0x00, // Input (Data,Arr,Abs) 37
84 * # 0xc0, // End Collection 39
85 * # 0x05, 0x0c, // Usage Page (Consumer) 40
86 * # 0x09, 0x01, // Usage (Consumer Control) 42
87 * # 0xa1, 0x01, // Collection (Application) 44
88 * # 0x85, 0x04, // Report ID (4) 46
89 * # 0x05, 0x0c, // Usage Page (Consumer) 48
90 * # 0x19, 0x00, // UsageMinimum (0) 50
91 * # 0x2a, 0x80, 0x03, // UsageMaximum (896) 52
92 * # 0x15, 0x00, // Logical Minimum (0) 55
93 * # 0x26, 0x80, 0x03, // Logical Maximum (896) 57
94 * # 0x75, 0x10, // Report Size (16) 60
95 * # 0x95, 0x01, // Report Count (1) 62
96 * # 0x81, 0x00, // Input (Data,Arr,Abs) 64
97 * # 0xc0, // End Collection 66
98 * # 0x05, 0x01, // Usage Page (Generic Desktop) 67
99 * # 0x09, 0x02, // Usage (Mouse) 69
100 * # 0xa1, 0x01, // Collection (Application) 71
101 * # 0x09, 0x01, // Usage (Pointer) 73
102 * # 0x85, 0x05, // Report ID (5) 75
103 * # 0xa1, 0x00, // Collection (Physical) 77
104 * # 0x05, 0x09, // Usage Page (Button) 79
105 * # 0x19, 0x01, // UsageMinimum (1) 81
106 * # 0x29, 0x05, // UsageMaximum (5) 83
107 * # 0x15, 0x00, // Logical Minimum (0) 85
108 * # 0x25, 0x01, // Logical Maximum (1) 87
109 * # 0x95, 0x05, // Report Count (5) 89
110 * # 0x75, 0x01, // Report Size (1) 91
111 * # 0x81, 0x02, // Input (Data,Var,Abs) 93
112 * # 0x95, 0x01, // Report Count (1) 95
113 * # 0x75, 0x03, // Report Size (3) 97
114 * # 0x81, 0x01, // Input (Cnst,Arr,Abs) 99
115 * # 0x05, 0x01, // Usage Page (Generic Desktop) 101
116 * # 0x09, 0x30, // Usage (X) 103
117 * # 0x09, 0x31, // Usage (Y) 105
118 * # 0x16, 0x00, 0x80, // Logical Minimum (-32768) 107
119 * # 0x26, 0xff, 0x7f, // Logical Maximum (32767) 110
120 * # 0x75, 0x10, // Report Size (16) 113
121 * # 0x95, 0x02, // Report Count (2) 115
122 * # 0x81, 0x06, // Input (Data,Var,Rel) 117
123 * # 0x95, 0x01, // Report Count (1) 119
124 * # 0x75, 0x08, // Report Size (8) 121
125 * # 0x05, 0x01, // Usage Page (Generic Desktop) 123
126 * # 0x09, 0x38, // Usage (Wheel) 125
127 * # 0x15, 0x81, // Logical Minimum (-127) 127
128 * # 0x25, 0x7f, // Logical Maximum (127) 129
129 * # 0x81, 0x06, // Input (Data,Var,Rel) 131
130 * # 0xc0, // End Collection 133
131 * # 0xc0, // End Collection 134
132 * R: 135 05 01 09 06 a1 01 85 03 05 07 19 e0 29 e7 15 00 25 01 75 01 95 08 81 02 05 07 19 00 29 ff 26 ff 00 75 08 95 06 81 00 c0 05 0c 09 01 a1 01 85 04 05 0c 19 00 2a 80 03 15 00 26 80 03 75 10 95 01 81 00 c0 05 01 09 02 a1 01 09 01 85 05 a1 00 05 09 19 01 29 05 15 00 25 01 95 05 75 01 81 02 95 01 75 03 81 01 05 01 09 30 09 31 16 00 80 26 ff 7f 7510 95 02 81 06 95 01 75 08 05 01 09 38 15 81 25 7f 81 06 c0 c0
133 *
134 * Third hidraw node is a multi-axis controller which sends the dial events
135 * and the button inside the dial. If the tablet is switched to raw mode it is mute.
136 *
137 * # HUION Huion Keydial_K20
138 * # Report descriptor length: 108 bytes
139 * # 0x05, 0x01, // Usage Page (Generic Desktop) 0
140 * # 0x09, 0x0e, // Usage (System Multi-Axis Controller) 2
141 * # 0xa1, 0x01, // Collection (Application) 4
142 * # 0x85, 0x11, // Report ID (17) 6
143 * # 0x05, 0x0d, // Usage Page (Digitizers) 8
144 * # 0x09, 0x21, // Usage (Puck) 10
145 * # 0xa1, 0x02, // Collection (Logical) 12
146 * # 0x15, 0x00, // Logical Minimum (0) 14
147 * # 0x25, 0x01, // Logical Maximum (1) 16
148 * # 0x75, 0x01, // Report Size (1) 18
149 * # 0x95, 0x01, // Report Count (1) 20
150 * # 0xa1, 0x00, // Collection (Physical) 22
151 * # 0x05, 0x09, // Usage Page (Button) 24
152 * # 0x09, 0x01, // Usage (Button 1) 26
153 * # 0x81, 0x02, // Input (Data,Var,Abs) 28
154 * # 0x05, 0x0d, // Usage Page (Digitizers) 30
155 * # 0x09, 0x33, // Usage (Touch) 32
156 * # 0x81, 0x02, // Input (Data,Var,Abs) 34
157 * # 0x95, 0x06, // Report Count (6) 36
158 * # 0x81, 0x03, // Input (Cnst,Var,Abs) 38
159 * # 0xa1, 0x02, // Collection (Logical) 40
160 * # 0x05, 0x01, // Usage Page (Generic Desktop) 42
161 * # 0x09, 0x37, // Usage (Dial) 44
162 * # 0x16, 0x00, 0x80, // Logical Minimum (-32768) 46
163 * # 0x26, 0xff, 0x7f, // Logical Maximum (32767) 49
164 * # 0x75, 0x10, // Report Size (16) 52
165 * # 0x95, 0x01, // Report Count (1) 54
166 * # 0x81, 0x06, // Input (Data,Var,Rel) 56
167 * # 0x35, 0x00, // Physical Minimum (0) 58
168 * # 0x46, 0x10, 0x0e, // Physical Maximum (3600) 60
169 * # 0x15, 0x00, // Logical Minimum (0) 63
170 * # 0x26, 0x10, 0x0e, // Logical Maximum (3600) 65
171 * # 0x09, 0x48, // Usage (Resolution Multiplier) 68
172 * # 0xb1, 0x02, // Feature (Data,Var,Abs) 70
173 * # 0x45, 0x00, // Physical Maximum (0) 72
174 * # 0xc0, // End Collection 74
175 * # 0x75, 0x08, // Report Size (8) 75
176 * # 0x95, 0x01, // Report Count (1) 77
177 * # 0x81, 0x01, // Input (Cnst,Arr,Abs) 79
178 * # 0x75, 0x08, // Report Size (8) 81
179 * # 0x95, 0x01, // Report Count (1) 83
180 * # 0x81, 0x01, // Input (Cnst,Arr,Abs) 85
181 * # 0x75, 0x08, // Report Size (8) 87
182 * # 0x95, 0x01, // Report Count (1) 89
183 * # 0x81, 0x01, // Input (Cnst,Arr,Abs) 91
184 * # 0x75, 0x08, // Report Size (8) 93
185 * # 0x95, 0x01, // Report Count (1) 95
186 * # 0x81, 0x01, // Input (Cnst,Arr,Abs) 97
187 * # 0x75, 0x08, // Report Size (8) 99
188 * # 0x95, 0x01, // Report Count (1) 101
189 * # 0x81, 0x01, // Input (Cnst,Arr,Abs) 103
190 * # 0xc0, // End Collection 105
191 * # 0xc0, // End Collection 106
192 * # 0xc0, // End Collection 107
193 * R: 108 05 01 09 0e a1 01 85 11 05 0d 09 21 a1 02 15 00 25 01 75 01 95 01 a1 00 05 09 09 01 81 02 05 0d 09 33 81 02 95 06 81 03 a1 02 05 01 09 37 16 00 80 26 ff 7f 75 10 95 01 81 06 35 00 46 10 0e 15 00 26 10 0e 09 48 b1 02 45 00 c0 75 08 95 01 81 01 75 08 95 01 81 01 75 08 95 01 81 01 75 08 95 01 81 01 75 08 95 01 81 01 c0 c0 c0
194 *
195 */
196
197 #define PAD_REPORT_DESCRIPTOR_LENGTH 135
198 #define PUCK_REPORT_DESCRIPTOR_LENGTH 108
199 #define VENDOR_REPORT_DESCRIPTOR_LENGTH 18
200 #define PAD_KBD_REPORT_ID 3
201 #define PAD_CC_REPORT_ID 3 // never sends events
202 #define PAD_MOUSE_REPORT_ID 4 // never sends events
203 #define PUCK_REPORT_ID 17
204 #define VENDOR_REPORT_ID 8
205 #define PAD_KBD_REPORT_LENGTH 8
206 #define PAD_CC_REPORT_LENGTH 3
207 #define PAD_MOUSE_REPORT_LENGTH 7
208 #define PUCK_REPORT_LENGTH 9
209 #define VENDOR_REPORT_LENGTH 12
210
211 __u32 last_button_state;
212
213 static const __u8 disabled_rdesc_puck[] = {
214 FixedSizeVendorReport(PUCK_REPORT_LENGTH)
215 };
216
217 static const __u8 disabled_rdesc_pad[] = {
218 FixedSizeVendorReport(PAD_KBD_REPORT_LENGTH)
219 FixedSizeVendorReport(PAD_CC_REPORT_LENGTH)
220 FixedSizeVendorReport(PAD_MOUSE_REPORT_LENGTH)
221 };
222
223 static const __u8 fixed_rdesc_vendor[] = {
224 UsagePage_GenericDesktop
225 Usage_GD_Keypad
226 CollectionApplication(
227 // Byte 0
228 // We send our pad events on the vendor report id because why not
229 ReportId(VENDOR_REPORT_ID)
230 UsagePage_Digitizers
231 Usage_Dig_TabletFunctionKeys
232 CollectionPhysical(
233 // Byte 1 is a button so we look like a tablet
234 Usage_Dig_BarrelSwitch // BTN_STYLUS, needed so we get to be a tablet pad
235 ReportCount(1)
236 ReportSize(1)
237 Input(Var|Abs)
238 ReportCount(7) // Padding
239 Input(Const)
240 // Bytes 2/3 - x/y just exist so we get to be a tablet pad
241 UsagePage_GenericDesktop
242 Usage_GD_X
243 Usage_GD_Y
244 LogicalMinimum_i8(0x0)
245 LogicalMaximum_i8(0x1)
246 ReportCount(2)
247 ReportSize(8)
248 Input(Var|Abs)
249 // Bytes 4-7 are the button state for 19 buttons + pad out to u32
250 // We send the first 10 buttons as buttons 1-10 which is BTN_0 -> BTN_9
251 UsagePage_Button
252 UsageMinimum_i8(1)
253 UsageMaximum_i8(10)
254 LogicalMinimum_i8(0x0)
255 LogicalMaximum_i8(0x1)
256 ReportCount(10)
257 ReportSize(1)
258 Input(Var|Abs)
259 // We send the other 9 buttons as buttons 0x31 and above -> BTN_A - BTN_TL2
260 UsageMinimum_i8(0x31)
261 UsageMaximum_i8(0x3a)
262 ReportCount(9)
263 ReportSize(1)
264 Input(Var|Abs)
265 ReportCount(13)
266 ReportSize(1)
267 Input(Const) // padding
268 // Byte 6 is the wheel
269 UsagePage_GenericDesktop
270 Usage_GD_Wheel
271 LogicalMinimum_i8(-1)
272 LogicalMaximum_i8(1)
273 ReportCount(1)
274 ReportSize(8)
275 Input(Var|Rel)
276 )
277 // Make sure we match our original report length
278 FixedSizeVendorReport(VENDOR_REPORT_LENGTH)
279 )
280 };
281
282 /* Identical to fixed_rdesc_pad but with different FixedSizeVendorReport */
283 static const __u8 fixed_rdesc_pad[] = {
284 UsagePage_GenericDesktop
285 Usage_GD_Keypad
286 CollectionApplication(
287 // Byte 0
288 // We send our pad events on the vendor report id because why not
289 ReportId(VENDOR_REPORT_ID)
290 UsagePage_Digitizers
291 Usage_Dig_TabletFunctionKeys
292 CollectionPhysical(
293 // Byte 1 is a button so we look like a tablet
294 Usage_Dig_BarrelSwitch // BTN_STYLUS, needed so we get to be a tablet pad
295 ReportCount(1)
296 ReportSize(1)
297 Input(Var|Abs)
298 ReportCount(7) // Padding
299 Input(Const)
300 // Bytes 2/3 - x/y just exist so we get to be a tablet pad
301 UsagePage_GenericDesktop
302 Usage_GD_X
303 Usage_GD_Y
304 LogicalMinimum_i8(0x0)
305 LogicalMaximum_i8(0x1)
306 ReportCount(2)
307 ReportSize(8)
308 Input(Var|Abs)
309 // Bytes 4-7 are the button state for 19 buttons + pad out to u32
310 // We send the first 10 buttons as buttons 1-10 which is BTN_0 -> BTN_9
311 UsagePage_Button
312 UsageMinimum_i8(1)
313 UsageMaximum_i8(10)
314 LogicalMinimum_i8(0x0)
315 LogicalMaximum_i8(0x1)
316 ReportCount(10)
317 ReportSize(1)
318 Input(Var|Abs)
319 // We send the other 9 buttons as buttons 0x31 and above -> BTN_A - BTN_TL2
320 UsageMinimum_i8(0x31)
321 UsageMaximum_i8(0x3a)
322 ReportCount(9)
323 ReportSize(1)
324 Input(Var|Abs)
325 ReportCount(13)
326 ReportSize(1)
327 Input(Const) // padding
328 // Byte 6 is the wheel
329 UsagePage_GenericDesktop
330 Usage_GD_Wheel
331 LogicalMinimum_i8(-1)
332 LogicalMaximum_i8(1)
333 ReportCount(1)
334 ReportSize(8)
335 Input(Var|Rel)
336 )
337 // Make sure we match our original report lengths
338 FixedSizeVendorReport(PAD_KBD_REPORT_LENGTH)
339 FixedSizeVendorReport(PAD_CC_REPORT_LENGTH)
340 FixedSizeVendorReport(PAD_MOUSE_REPORT_LENGTH)
341 )
342 };
343
SEC(HID_BPF_RDESC_FIXUP)344 SEC(HID_BPF_RDESC_FIXUP)
345 int BPF_PROG(k20_fix_rdesc, struct hid_bpf_ctx *hctx)
346 {
347 __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, HID_MAX_DESCRIPTOR_SIZE /* size */);
348 __s32 rdesc_size = hctx->size;
349 __u8 have_fw_id;
350
351 if (!data)
352 return 0; /* EPERM check */
353
354 /* If we have a firmware ID and it matches our expected prefix, we
355 * disable the default pad/puck nodes. They won't send events
356 * but cause duplicate devices.
357 */
358 have_fw_id = __builtin_memcmp(UDEV_PROP_HUION_FIRMWARE_ID,
359 EXPECTED_FIRMWARE_ID,
360 sizeof(EXPECTED_FIRMWARE_ID) - 1) == 0;
361 if (rdesc_size == PAD_REPORT_DESCRIPTOR_LENGTH) {
362 if (have_fw_id) {
363 __builtin_memcpy(data, disabled_rdesc_pad, sizeof(disabled_rdesc_pad));
364 return sizeof(disabled_rdesc_pad);
365 } else {
366 __builtin_memcpy(data, fixed_rdesc_pad, sizeof(fixed_rdesc_pad));
367 return sizeof(fixed_rdesc_pad);
368
369 }
370 }
371 if (rdesc_size == PUCK_REPORT_DESCRIPTOR_LENGTH) {
372 if (have_fw_id) {
373 __builtin_memcpy(data, disabled_rdesc_puck, sizeof(disabled_rdesc_puck));
374 return sizeof(disabled_rdesc_puck);
375 }
376 }
377 /* Always fix the vendor mode so the tablet will work even if nothing sets
378 * the udev property (e.g. huion-switcher run manually)
379 */
380 if (rdesc_size == VENDOR_REPORT_DESCRIPTOR_LENGTH) {
381 __builtin_memcpy(data, fixed_rdesc_vendor, sizeof(fixed_rdesc_vendor));
382 return sizeof(fixed_rdesc_vendor);
383
384 }
385 return 0;
386 }
387
SEC(HID_BPF_DEVICE_EVENT)388 SEC(HID_BPF_DEVICE_EVENT)
389 int BPF_PROG(k20_fix_events, struct hid_bpf_ctx *hctx)
390 {
391 __u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 10 /* size */);
392
393 if (!data)
394 return 0; /* EPERM check */
395
396 /* Only sent if tablet is in raw mode */
397 if (data[0] == VENDOR_REPORT_ID) {
398 /* See fixed_rdesc_pad */
399 struct pad_report {
400 __u8 report_id;
401 __u8 btn_stylus:1;
402 __u8 pad:7;
403 __u8 x;
404 __u8 y;
405 __u32 buttons;
406 __u8 wheel;
407 } __attribute__((packed)) *pad_report;
408
409 __u8 wheel = 0;
410
411 /* Wheel report */
412 if (data[1] == 0xf1) {
413 if (data[5] == 2)
414 wheel = 0xff;
415 else
416 wheel = data[5];
417 } else {
418 /* data[4..6] are the buttons, mapped correctly */
419 last_button_state = data[4] | (data[5] << 8) | (data[6] << 16);
420 wheel = 0; // wheel
421 }
422
423 pad_report = (struct pad_report *)data;
424 pad_report->report_id = VENDOR_REPORT_ID;
425 pad_report->btn_stylus = 0;
426 pad_report->x = 0;
427 pad_report->y = 0;
428 pad_report->buttons = last_button_state;
429 pad_report->wheel = wheel;
430
431 return sizeof(struct pad_report);
432 }
433
434 if (data[0] == PAD_KBD_REPORT_ID) {
435 const __u8 button_mapping[] = {
436 0x0e, /* Button 1: K */
437 0x0a, /* Button 2: G */
438 0x0f, /* Button 3: L */
439 0x4c, /* Button 4: Delete */
440 0x0c, /* Button 5: I */
441 0x07, /* Button 6: D */
442 0x05, /* Button 7: B */
443 0x08, /* Button 8: E */
444 0x16, /* Button 9: S */
445 0x1d, /* Button 10: Z */
446 0x06, /* Button 11: C */
447 0x19, /* Button 12: V */
448 0xff, /* Button 13: LeftControl */
449 0xff, /* Button 14: LeftAlt */
450 0xff, /* Button 15: LeftShift */
451 0x28, /* Button 16: Return Enter */
452 0x2c, /* Button 17: Spacebar */
453 0x11, /* Button 18: N */
454 };
455 /* See fixed_rdesc_pad */
456 struct pad_report {
457 __u8 report_id;
458 __u8 btn_stylus:1;
459 __u8 pad:7;
460 __u8 x;
461 __u8 y;
462 __u32 buttons;
463 __u8 wheel;
464 } __attribute__((packed)) *pad_report;
465 int i, b;
466 __u8 modifiers = data[1];
467 __u32 buttons = 0;
468
469 if (modifiers & 0x01) { /* Control */
470 buttons |= BIT(12);
471 }
472 if (modifiers & 0x02) { /* Shift */
473 buttons |= BIT(14);
474 }
475 if (modifiers & 0x04) { /* Alt */
476 buttons |= BIT(13);
477 }
478
479 for (i = 2; i < PAD_KBD_REPORT_LENGTH; i++) {
480 if (!data[i])
481 break;
482
483 for (b = 0; b < ARRAY_SIZE(button_mapping); b++) {
484 if (data[i] == button_mapping[b]) {
485 buttons |= BIT(b);
486 break;
487 }
488 }
489 data[i] = 0;
490 }
491
492 pad_report = (struct pad_report *)data;
493 pad_report->report_id = VENDOR_REPORT_ID;
494 pad_report->btn_stylus = 0;
495 pad_report->x = 0;
496 pad_report->y = 0;
497 pad_report->buttons = buttons;
498 // The wheel happens on a different hidraw node but its
499 // values are unreliable (as is the button inside the wheel).
500 // So the wheel is simply always zero, if you want the wheel
501 // to work reliably, use the tablet mode.
502 pad_report->wheel = 0;
503
504 return sizeof(struct pad_report);
505 }
506
507 return 0;
508 }
509
510 HID_BPF_OPS(keydial_k20) = {
511 .hid_device_event = (void *)k20_fix_events,
512 .hid_rdesc_fixup = (void *)k20_fix_rdesc,
513 };
514
515 SEC("syscall")
probe(struct hid_bpf_probe_args * ctx)516 int probe(struct hid_bpf_probe_args *ctx)
517 {
518 switch (ctx->rdesc_size) {
519 case PAD_REPORT_DESCRIPTOR_LENGTH:
520 case PUCK_REPORT_DESCRIPTOR_LENGTH:
521 case VENDOR_REPORT_DESCRIPTOR_LENGTH:
522 ctx->retval = 0;
523 break;
524 default:
525 ctx->retval = -EINVAL;
526 }
527
528 return 0;
529 }
530
531 char _license[] SEC("license") = "GPL";
532