1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (c) 2021 Hans de Goede <hdegoede@redhat.com>
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 <asm/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 = from_timer(data, t, inrange_timer);
159	struct input_dev *input = data->input_tablet;
160
161	input_report_key(input, BTN_TOOL_PEN, 0);
162	input_sync(input);
163}
164
165static int letsketch_raw_event(struct hid_device *hdev,
166			       struct hid_report *report,
167			       u8 *raw_data, int size)
168{
169	struct letsketch_data *data = hid_get_drvdata(hdev);
170	struct input_dev *input;
171	int i;
172
173	if (size != LETSKETCH_RAW_DATA_LEN || raw_data[0] != LETSKETCH_RAW_REPORT_ID)
174		return 0;
175
176	switch (raw_data[1] & 0xf0) {
177	case 0x80: /* Pen data */
178		input = data->input_tablet;
179		input_report_key(input, BTN_TOOL_PEN, 1);
180		input_report_key(input, BTN_TOUCH, raw_data[1] & 0x01);
181		input_report_key(input, BTN_STYLUS, raw_data[1] & 0x02);
182		input_report_key(input, BTN_STYLUS2, raw_data[1] & 0x04);
183		input_report_abs(input, ABS_X,
184				 get_unaligned_le16(raw_data + 2));
185		input_report_abs(input, ABS_Y,
186				 get_unaligned_le16(raw_data + 4));
187		input_report_abs(input, ABS_PRESSURE,
188				 get_unaligned_le16(raw_data + 6));
189		/*
190		 * There is no out of range event, so use a timer for this
191		 * when in range we get an event approx. every 8 ms.
192		 */
193		mod_timer(&data->inrange_timer, jiffies + msecs_to_jiffies(100));
194		break;
195	case 0xe0: /* Pad data */
196		input = data->input_tablet_pad;
197		for (i = 0; i < LETSKETCH_PAD_BUTTONS; i++)
198			input_report_key(input, BTN_0 + i, raw_data[4] == (i + 1));
199		break;
200	default:
201		hid_warn(data->hdev, "Warning unknown data header: 0x%02x\n",
202			 raw_data[0]);
203		return 0;
204	}
205
206	input_sync(input);
207	return 0;
208}
209
210/*
211 * The tablets magic handshake to put it in raw mode relies on getting
212 * string descriptors. But the firmware is buggy and does not like it if
213 * we do this too fast. Even if we go slow sometimes the usb_string() call
214 * fails. Ignore errors and retry it a couple of times if necessary.
215 */
216static int letsketch_get_string(struct usb_device *udev, int index, char *buf, int size)
217{
218	int i, ret;
219
220	for (i = 0; i < LETSKETCH_GET_STRING_RETRIES; i++) {
221		usleep_range(5000, 7000);
222		ret = usb_string(udev, index, buf, size);
223		if (ret > 0)
224			return 0;
225	}
226
227	dev_err(&udev->dev, "Max retries (%d) exceeded reading string descriptor %d\n",
228		LETSKETCH_GET_STRING_RETRIES, index);
229	return ret ? ret : -EIO;
230}
231
232static int letsketch_probe(struct hid_device *hdev, const struct hid_device_id *id)
233{
234	struct device *dev = &hdev->dev;
235	struct letsketch_data *data;
236	struct usb_interface *intf;
237	struct usb_device *udev;
238	char buf[256];
239	int i, ret;
240
241	if (!hid_is_usb(hdev))
242		return -ENODEV;
243
244	intf = to_usb_interface(hdev->dev.parent);
245	if (intf->altsetting->desc.bInterfaceNumber != LETSKETCH_RAW_IF)
246		return -ENODEV; /* Ignore the other interfaces */
247
248	udev = interface_to_usbdev(intf);
249
250	/*
251	 * Instead of using a set-feature request, or even a custom USB ctrl
252	 * message the tablet needs this elaborate magic reading of USB
253	 * string descriptors to kick it into raw mode. This is what the
254	 * Windows drivers are seen doing in an USB trace under Windows.
255	 */
256	for (i = LETSKETCH_INFO_STR_IDX_BEGIN; i <= LETSKETCH_INFO_STR_IDX_END; i++) {
257		ret = letsketch_get_string(udev, i, buf, sizeof(buf));
258		if (ret)
259			return ret;
260
261		hid_info(hdev, "Device info: %s\n", buf);
262	}
263
264	for (i = 1; i <= 250; i++) {
265		ret = letsketch_get_string(udev, i, buf, sizeof(buf));
266		if (ret)
267			return ret;
268	}
269
270	ret = letsketch_get_string(udev, 0x64, buf, sizeof(buf));
271	if (ret)
272		return ret;
273
274	ret = letsketch_get_string(udev, LETSKETCH_INFO_STR_IDX_BEGIN, buf, sizeof(buf));
275	if (ret)
276		return ret;
277
278	/*
279	 * The tablet should be in raw mode now, end with a final delay before
280	 * doing further IO to the device.
281	 */
282	usleep_range(5000, 7000);
283
284	ret = hid_parse(hdev);
285	if (ret)
286		return ret;
287
288	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
289	if (!data)
290		return -ENOMEM;
291
292	data->hdev = hdev;
293	timer_setup(&data->inrange_timer, letsketch_inrange_timeout, 0);
294	hid_set_drvdata(hdev, data);
295
296	ret = letsketch_setup_input_tablet(data);
297	if (ret)
298		return ret;
299
300	ret = letsketch_setup_input_tablet_pad(data);
301	if (ret)
302		return ret;
303
304	return hid_hw_start(hdev, HID_CONNECT_HIDRAW);
305}
306
307static const struct hid_device_id letsketch_devices[] = {
308	{ HID_USB_DEVICE(USB_VENDOR_ID_LETSKETCH, USB_DEVICE_ID_WP9620N) },
309	{ }
310};
311MODULE_DEVICE_TABLE(hid, letsketch_devices);
312
313static struct hid_driver letsketch_driver = {
314	.name = "letsketch",
315	.id_table = letsketch_devices,
316	.probe = letsketch_probe,
317	.raw_event = letsketch_raw_event,
318};
319module_hid_driver(letsketch_driver);
320
321MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
322MODULE_LICENSE("GPL");
323