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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (c) 2021 Hans de Goede <[email protected]>
4 *
5 * Driver for the LetSketch / VSON WP9620N drawing tablet.
6 * This drawing tablet is also sold under other brand names such as Case U,
7 * presumably this driver will work for all of them. But it has only been
8 * tested with a LetSketch WP9620N model.
9 *
10 * These tablets also work without a special HID driver, but then only part
11 * of the active area works and both the pad and stylus buttons are hardwired
12 * to special key-combos. E.g. the 2 stylus buttons send right mouse clicks /
13 * resp. "e" key presses.
14 *
15 * This device has 4 USB interfaces:
16 *
17 * Interface 0 EP 0x81 bootclass mouse, rdesc len 18, report id 0x08,
18 * Application(ff00.0001)
19 * This interface sends raw event input reports in a custom format, but only
20 * after doing the special dance from letsketch_probe(). After enabling this
21 * interface the other 3 interfaces are disabled.
22 *
23 * Interface 1 EP 0x82 bootclass mouse, rdesc len 83, report id 0x0a, Tablet
24 * This interface sends absolute events for the pen, including pressure,
25 * but only for some part of the active area due to special "aspect ratio"
26 * correction and only half by default since it assumes it will be used
27 * with a phone in portraid mode, while using the tablet in landscape mode.
28 * Also stylus + pad button events are not reported here.
29 *
30 * Interface 2 EP 0x83 bootclass keybd, rdesc len 64, report id none, Std Kbd
31 * This interfaces send various hard-coded key-combos for the pad buttons
32 * and "e" keypresses for the 2nd stylus button
33 *
34 * Interface 3 EP 0x84 bootclass mouse, rdesc len 75, report id 0x01, Std Mouse
35 * This reports right-click mouse-button events for the 1st stylus button
36 */
37#include <linux/device.h>
38#include <linux/input.h>
39#include <linux/hid.h>
40#include <linux/module.h>
41#include <linux/timer.h>
42#include <linux/usb.h>
43
44#include <linux/unaligned.h>
45
46#include "hid-ids.h"
47
48#define LETSKETCH_RAW_IF 0
49
50#define LETSKETCH_RAW_DATA_LEN 12
51#define LETSKETCH_RAW_REPORT_ID 8
52
53#define LETSKETCH_PAD_BUTTONS 5
54
55#define LETSKETCH_INFO_STR_IDX_BEGIN 0xc8
56#define LETSKETCH_INFO_STR_IDX_END 0xca
57
58#define LETSKETCH_GET_STRING_RETRIES 5
59
60struct letsketch_data {
61 struct hid_device *hdev;
62 struct input_dev *input_tablet;
63 struct input_dev *input_tablet_pad;
64 struct timer_list inrange_timer;
65};
66
67static int letsketch_open(struct input_dev *dev)
68{
69 struct letsketch_data *data = input_get_drvdata(dev);
70
71 return hid_hw_open(data->hdev);
72}
73
74static void letsketch_close(struct input_dev *dev)
75{
76 struct letsketch_data *data = input_get_drvdata(dev);
77
78 hid_hw_close(data->hdev);
79}
80
81static struct input_dev *letsketch_alloc_input_dev(struct letsketch_data *data)
82{
83 struct input_dev *input;
84
85 input = devm_input_allocate_device(&data->hdev->dev);
86 if (!input)
87 return NULL;
88
89 input->id.bustype = data->hdev->bus;
90 input->id.vendor = data->hdev->vendor;
91 input->id.product = data->hdev->product;
92 input->id.version = data->hdev->bus;
93 input->phys = data->hdev->phys;
94 input->uniq = data->hdev->uniq;
95 input->open = letsketch_open;
96 input->close = letsketch_close;
97
98 input_set_drvdata(input, data);
99
100 return input;
101}
102
103static int letsketch_setup_input_tablet(struct letsketch_data *data)
104{
105 struct input_dev *input;
106
107 input = letsketch_alloc_input_dev(data);
108 if (!input)
109 return -ENOMEM;
110
111 input_set_abs_params(input, ABS_X, 0, 50800, 0, 0);
112 input_set_abs_params(input, ABS_Y, 0, 31750, 0, 0);
113 input_set_abs_params(input, ABS_PRESSURE, 0, 8192, 0, 0);
114 input_abs_set_res(input, ABS_X, 240);
115 input_abs_set_res(input, ABS_Y, 225);
116 input_set_capability(input, EV_KEY, BTN_TOUCH);
117 input_set_capability(input, EV_KEY, BTN_TOOL_PEN);
118 input_set_capability(input, EV_KEY, BTN_STYLUS);
119 input_set_capability(input, EV_KEY, BTN_STYLUS2);
120
121 /* All known brands selling this tablet use WP9620[N] as model name */
122 input->name = "WP9620 Tablet";
123
124 data->input_tablet = input;
125
126 return input_register_device(data->input_tablet);
127}
128
129static int letsketch_setup_input_tablet_pad(struct letsketch_data *data)
130{
131 struct input_dev *input;
132 int i;
133
134 input = letsketch_alloc_input_dev(data);
135 if (!input)
136 return -ENOMEM;
137
138 for (i = 0; i < LETSKETCH_PAD_BUTTONS; i++)
139 input_set_capability(input, EV_KEY, BTN_0 + i);
140
141 /*
142 * These are never send on the pad input_dev, but must be set
143 * on the Pad to make udev / libwacom happy.
144 */
145 input_set_abs_params(input, ABS_X, 0, 1, 0, 0);
146 input_set_abs_params(input, ABS_Y, 0, 1, 0, 0);
147 input_set_capability(input, EV_KEY, BTN_STYLUS);
148
149 input->name = "WP9620 Pad";
150
151 data->input_tablet_pad = input;
152
153 return input_register_device(data->input_tablet_pad);
154}
155
156static void letsketch_inrange_timeout(struct timer_list *t)
157{
158 struct letsketch_data *data = timer_container_of(data, t,
159 inrange_timer);
160 struct input_dev *input = data->input_tablet;
161
162 input_report_key(input, BTN_TOOL_PEN, 0);
163 input_sync(input);
164}
165
166static int letsketch_raw_event(struct hid_device *hdev,
167 struct hid_report *report,
168 u8 *raw_data, int size)
169{
170 struct letsketch_data *data = hid_get_drvdata(hdev);
171 struct input_dev *input;
172 int i;
173
174 if (size != LETSKETCH_RAW_DATA_LEN || raw_data[0] != LETSKETCH_RAW_REPORT_ID)
175 return 0;
176
177 switch (raw_data[1] & 0xf0) {
178 case 0x80: /* Pen data */
179 input = data->input_tablet;
180 input_report_key(input, BTN_TOOL_PEN, 1);
181 input_report_key(input, BTN_TOUCH, raw_data[1] & 0x01);
182 input_report_key(input, BTN_STYLUS, raw_data[1] & 0x02);
183 input_report_key(input, BTN_STYLUS2, raw_data[1] & 0x04);
184 input_report_abs(input, ABS_X,
185 get_unaligned_le16(raw_data + 2));
186 input_report_abs(input, ABS_Y,
187 get_unaligned_le16(raw_data + 4));
188 input_report_abs(input, ABS_PRESSURE,
189 get_unaligned_le16(raw_data + 6));
190 /*
191 * There is no out of range event, so use a timer for this
192 * when in range we get an event approx. every 8 ms.
193 */
194 mod_timer(&data->inrange_timer, jiffies + msecs_to_jiffies(100));
195 break;
196 case 0xe0: /* Pad data */
197 input = data->input_tablet_pad;
198 for (i = 0; i < LETSKETCH_PAD_BUTTONS; i++)
199 input_report_key(input, BTN_0 + i, raw_data[4] == (i + 1));
200 break;
201 default:
202 hid_warn(data->hdev, "Warning unknown data header: 0x%02x\n",
203 raw_data[0]);
204 return 0;
205 }
206
207 input_sync(input);
208 return 0;
209}
210
211/*
212 * The tablets magic handshake to put it in raw mode relies on getting
213 * string descriptors. But the firmware is buggy and does not like it if
214 * we do this too fast. Even if we go slow sometimes the usb_string() call
215 * fails. Ignore errors and retry it a couple of times if necessary.
216 */
217static int letsketch_get_string(struct usb_device *udev, int index, char *buf, int size)
218{
219 int i, ret;
220
221 for (i = 0; i < LETSKETCH_GET_STRING_RETRIES; i++) {
222 usleep_range(5000, 7000);
223 ret = usb_string(udev, index, buf, size);
224 if (ret > 0)
225 return 0;
226 }
227
228 dev_err(&udev->dev, "Max retries (%d) exceeded reading string descriptor %d\n",
229 LETSKETCH_GET_STRING_RETRIES, index);
230 return ret ? ret : -EIO;
231}
232
233static int letsketch_probe(struct hid_device *hdev, const struct hid_device_id *id)
234{
235 struct device *dev = &hdev->dev;
236 struct letsketch_data *data;
237 struct usb_interface *intf;
238 struct usb_device *udev;
239 char buf[256];
240 int i, ret;
241
242 if (!hid_is_usb(hdev))
243 return -ENODEV;
244
245 intf = to_usb_interface(hdev->dev.parent);
246 if (intf->altsetting->desc.bInterfaceNumber != LETSKETCH_RAW_IF)
247 return -ENODEV; /* Ignore the other interfaces */
248
249 udev = interface_to_usbdev(intf);
250
251 /*
252 * Instead of using a set-feature request, or even a custom USB ctrl
253 * message the tablet needs this elaborate magic reading of USB
254 * string descriptors to kick it into raw mode. This is what the
255 * Windows drivers are seen doing in an USB trace under Windows.
256 */
257 for (i = LETSKETCH_INFO_STR_IDX_BEGIN; i <= LETSKETCH_INFO_STR_IDX_END; i++) {
258 ret = letsketch_get_string(udev, i, buf, sizeof(buf));
259 if (ret)
260 return ret;
261
262 hid_info(hdev, "Device info: %s\n", buf);
263 }
264
265 for (i = 1; i <= 250; i++) {
266 ret = letsketch_get_string(udev, i, buf, sizeof(buf));
267 if (ret)
268 return ret;
269 }
270
271 ret = letsketch_get_string(udev, 0x64, buf, sizeof(buf));
272 if (ret)
273 return ret;
274
275 ret = letsketch_get_string(udev, LETSKETCH_INFO_STR_IDX_BEGIN, buf, sizeof(buf));
276 if (ret)
277 return ret;
278
279 /*
280 * The tablet should be in raw mode now, end with a final delay before
281 * doing further IO to the device.
282 */
283 usleep_range(5000, 7000);
284
285 ret = hid_parse(hdev);
286 if (ret)
287 return ret;
288
289 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
290 if (!data)
291 return -ENOMEM;
292
293 data->hdev = hdev;
294 timer_setup(&data->inrange_timer, letsketch_inrange_timeout, 0);
295 hid_set_drvdata(hdev, data);
296
297 ret = letsketch_setup_input_tablet(data);
298 if (ret)
299 goto err_shutdown_timer;
300
301 ret = letsketch_setup_input_tablet_pad(data);
302 if (ret)
303 goto err_shutdown_timer;
304
305 ret = hid_hw_start(hdev, HID_CONNECT_HIDRAW);
306 if (ret)
307 goto err_shutdown_timer;
308
309 return 0;
310
311err_shutdown_timer:
312 /*
313 * Drain any pending callback and permanently disable the timer
314 * before devm releases data: if hid_hw_start() enabled I/O on an
315 * always-poll-quirk device and then failed, raw_event may have
316 * armed the timer already.
317 */
318 timer_shutdown_sync(&data->inrange_timer);
319 return ret;
320}
321
322static void letsketch_remove(struct hid_device *hdev)
323{
324 struct letsketch_data *data = hid_get_drvdata(hdev);
325
326 /*
327 * hid_hw_stop() synchronously kills the URBs that deliver
328 * raw_event(), so once it returns no path can re-arm
329 * inrange_timer. timer_shutdown_sync() then drains any
330 * in-flight callback and permanently disables further
331 * mod_timer() calls before devm releases data.
332 */
333 hid_hw_stop(hdev);
334 timer_shutdown_sync(&data->inrange_timer);
335}
336
337static const struct hid_device_id letsketch_devices[] = {
338 { HID_USB_DEVICE(USB_VENDOR_ID_LETSKETCH, USB_DEVICE_ID_WP9620N) },
339 { }
340};
341MODULE_DEVICE_TABLE(hid, letsketch_devices);
342
343static struct hid_driver letsketch_driver = {
344 .name = "letsketch",
345 .id_table = letsketch_devices,
346 .probe = letsketch_probe,
347 .remove = letsketch_remove,
348 .raw_event = letsketch_raw_event,
349};
350module_hid_driver(letsketch_driver);
351
352MODULE_AUTHOR("Hans de Goede <[email protected]>");
353MODULE_DESCRIPTION("Driver for the LetSketch / VSON WP9620N drawing tablet");
354MODULE_LICENSE("GPL");