hid-letsketch.c

  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 <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		return ret;
300
301	ret = letsketch_setup_input_tablet_pad(data);
302	if (ret)
303		return ret;
304
305	return hid_hw_start(hdev, HID_CONNECT_HIDRAW);
306}
307
308static const struct hid_device_id letsketch_devices[] = {
309	{ HID_USB_DEVICE(USB_VENDOR_ID_LETSKETCH, USB_DEVICE_ID_WP9620N) },
310	{ }
311};
312MODULE_DEVICE_TABLE(hid, letsketch_devices);
313
314static struct hid_driver letsketch_driver = {
315	.name = "letsketch",
316	.id_table = letsketch_devices,
317	.probe = letsketch_probe,
318	.raw_event = letsketch_raw_event,
319};
320module_hid_driver(letsketch_driver);
321
322MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
323MODULE_DESCRIPTION("Driver for the LetSketch / VSON WP9620N drawing tablet");
324MODULE_LICENSE("GPL");