HID: Add new Letsketch tablet driver

Add a new driver for the LetSketch / VSON WP9620N drawing tablet. This
drawing tablet is also sold under other brand names such as Case U,
presumably this driver will work for all of them. But it has only been
tested with a LetSketch WP9620N model.

These tablets also work without a special HID driver, but then only
part of the active area works and both the pad and stylus buttons are
hardwired to special key-combos. E.g. the 2 stylus buttons send right
mouse clicks / resp. "e" key presses.

BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=2005575
BugLink: https://github.com/DIGImend/digimend-kernel-drivers/issues/528Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

MAINTAINERS

@@ -10745,6 +10745,13 @@ S:	Maintained
 W:	http://legousb.sourceforge.net/
 F:	drivers/usb/misc/legousbtower.c
 
+LETSKETCH HID TABLET DRIVER
+M:	Hans de Goede <hdegoede@redhat.com>
+L:	linux-input@vger.kernel.org
+S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid.git
+F:	drivers/hid/hid-letsketch.c
+
 LG LAPTOP EXTRAS
 M:	Matan Ziv-Av <matan@svgalib.org>
 L:	platform-driver-x86@vger.kernel.org

drivers/hid/Kconfig

@@ -558,6 +558,20 @@ config HID_LENOVO
 	- ThinkPad Compact Bluetooth Keyboard with TrackPoint (supports Fn keys)
 	- ThinkPad Compact USB Keyboard with TrackPoint (supports Fn keys)
 
+config HID_LETSKETCH
+	tristate "Letsketch WP9620N tablets"
+	depends on USB_HID
+	help
+	  Driver for the LetSketch / VSON WP9620N drawing tablet. This
+	  drawing tablet is also sold under other brand names such as Case U,
+	  presumably this driver will work for all of them. But it has only been
+	  tested with a LetSketch WP9620N model.
+
+	  These tablets also work without a special HID driver, but then only
+	  part of the active area works and both the pad and stylus buttons are
+	  hardwired to special key-combos. E.g. the 2 stylus buttons send right
+	  mouse clicks / resp. "e" key presses.
+
 config HID_LOGITECH
 	tristate "Logitech devices"
 	depends on USB_HID

drivers/hid/Makefile

@@ -66,6 +66,7 @@ obj-$(CONFIG_HID_KEYTOUCH)	+= hid-keytouch.o
 obj-$(CONFIG_HID_KYE)		+= hid-kye.o
 obj-$(CONFIG_HID_LCPOWER)	+= hid-lcpower.o
 obj-$(CONFIG_HID_LENOVO)	+= hid-lenovo.o
+obj-$(CONFIG_HID_LETSKETCH)	+= hid-letsketch.o
 obj-$(CONFIG_HID_LOGITECH)	+= hid-logitech.o
 obj-$(CONFIG_HID_LOGITECH)	+= hid-lg-g15.o
 obj-$(CONFIG_HID_LOGITECH_DJ)	+= hid-logitech-dj.o

drivers/hid/hid-ids.h

@@ -763,6 +763,9 @@
 #define USB_DEVICE_ID_LENOVO_PIXART_USB_MOUSE_602E	0x602e
 #define USB_DEVICE_ID_LENOVO_PIXART_USB_MOUSE_6093	0x6093
 
+#define USB_VENDOR_ID_LETSKETCH		0x6161
+#define USB_DEVICE_ID_WP9620N		0x4d15
+
 #define USB_VENDOR_ID_LG		0x1fd2
 #define USB_DEVICE_ID_LG_MULTITOUCH	0x0064
 #define USB_DEVICE_ID_LG_MELFAS_MT	0x6007

drivers/hid/hid-letsketch.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2021 Hans de Goede <hdegoede@redhat.com>
+ *
+ * Driver for the LetSketch / VSON WP9620N drawing tablet.
+ * This drawing tablet is also sold under other brand names such as Case U,
+ * presumably this driver will work for all of them. But it has only been
+ * tested with a LetSketch WP9620N model.
+ *
+ * These tablets also work without a special HID driver, but then only part
+ * of the active area works and both the pad and stylus buttons are hardwired
+ * to special key-combos. E.g. the 2 stylus buttons send right mouse clicks /
+ * resp. "e" key presses.
+ *
+ * This device has 4 USB interfaces:
+ *
+ * Interface 0 EP 0x81 bootclass mouse, rdesc len 18, report id 0x08,
+ *                                                    Application(ff00.0001)
+ *  This interface sends raw event input reports in a custom format, but only
+ *  after doing the special dance from letsketch_probe(). After enabling this
+ *  interface the other 3 interfaces are disabled.
+ *
+ * Interface 1 EP 0x82 bootclass mouse, rdesc len 83, report id 0x0a, Tablet
+ *  This interface sends absolute events for the pen, including pressure,
+ *  but only for some part of the active area due to special "aspect ratio"
+ *  correction and only half by default since it assumes it will be used
+ *  with a phone in portraid mode, while using the tablet in landscape mode.
+ *  Also stylus + pad button events are not reported here.
+ *
+ * Interface 2 EP 0x83 bootclass keybd, rdesc len 64, report id none, Std Kbd
+ *  This interfaces send various hard-coded key-combos for the pad buttons
+ *  and "e" keypresses for the 2nd stylus button
+ *
+ * Interface 3 EP 0x84 bootclass mouse, rdesc len 75, report id 0x01, Std Mouse
+ *  This reports right-click mouse-button events for the 1st stylus button
+ */
+#include <linux/device.h>
+#include <linux/input.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+#include <linux/timer.h>
+#include <linux/usb.h>
+
+#include <asm/unaligned.h>
+
+#include "hid-ids.h"
+
+#define LETSKETCH_RAW_IF		0
+
+#define LETSKETCH_RAW_DATA_LEN		12
+#define LETSKETCH_RAW_REPORT_ID		8
+
+#define LETSKETCH_PAD_BUTTONS		5
+
+#define LETSKETCH_INFO_STR_IDX_BEGIN	0xc8
+#define LETSKETCH_INFO_STR_IDX_END	0xca
+
+#define LETSKETCH_GET_STRING_RETRIES	5
+
+struct letsketch_data {
+	struct hid_device *hdev;
+	struct input_dev *input_tablet;
+	struct input_dev *input_tablet_pad;
+	struct timer_list inrange_timer;
+};
+
+static int letsketch_open(struct input_dev *dev)
+{
+	struct letsketch_data *data = input_get_drvdata(dev);
+
+	return hid_hw_open(data->hdev);
+}
+
+static void letsketch_close(struct input_dev *dev)
+{
+	struct letsketch_data *data = input_get_drvdata(dev);
+
+	hid_hw_close(data->hdev);
+}
+
+static struct input_dev *letsketch_alloc_input_dev(struct letsketch_data *data)
+{
+	struct input_dev *input;
+
+	input = devm_input_allocate_device(&data->hdev->dev);
+	if (!input)
+		return NULL;
+
+	input->id.bustype = data->hdev->bus;
+	input->id.vendor  = data->hdev->vendor;
+	input->id.product = data->hdev->product;
+	input->id.version = data->hdev->bus;
+	input->phys = data->hdev->phys;
+	input->uniq = data->hdev->uniq;
+	input->open = letsketch_open;
+	input->close = letsketch_close;
+
+	input_set_drvdata(input, data);
+
+	return input;
+}
+
+static int letsketch_setup_input_tablet(struct letsketch_data *data)
+{
+	struct input_dev *input;
+
+	input = letsketch_alloc_input_dev(data);
+	if (!input)
+		return -ENOMEM;
+
+	input_set_abs_params(input, ABS_X, 0, 50800, 0, 0);
+	input_set_abs_params(input, ABS_Y, 0, 31750, 0, 0);
+	input_set_abs_params(input, ABS_PRESSURE, 0, 8192, 0, 0);
+	input_abs_set_res(input, ABS_X, 240);
+	input_abs_set_res(input, ABS_Y, 225);
+	input_set_capability(input, EV_KEY, BTN_TOUCH);
+	input_set_capability(input, EV_KEY, BTN_TOOL_PEN);
+	input_set_capability(input, EV_KEY, BTN_STYLUS);
+	input_set_capability(input, EV_KEY, BTN_STYLUS2);
+
+	/* All known brands selling this tablet use WP9620[N] as model name */
+	input->name = "WP9620 Tablet";
+
+	data->input_tablet = input;
+
+	return input_register_device(data->input_tablet);
+}
+
+static int letsketch_setup_input_tablet_pad(struct letsketch_data *data)
+{
+	struct input_dev *input;
+	int i;
+
+	input = letsketch_alloc_input_dev(data);
+	if (!input)
+		return -ENOMEM;
+
+	for (i = 0; i < LETSKETCH_PAD_BUTTONS; i++)
+		input_set_capability(input, EV_KEY, BTN_0 + i);
+
+	/*
+	 * These are never send on the pad input_dev, but must be set
+	 * on the Pad to make udev / libwacom happy.
+	 */
+	input_set_abs_params(input, ABS_X, 0, 1, 0, 0);
+	input_set_abs_params(input, ABS_Y, 0, 1, 0, 0);
+	input_set_capability(input, EV_KEY, BTN_STYLUS);
+
+	input->name = "WP9620 Pad";
+
+	data->input_tablet_pad = input;
+
+	return input_register_device(data->input_tablet_pad);
+}
+
+static void letsketch_inrange_timeout(struct timer_list *t)
+{
+	struct letsketch_data *data = from_timer(data, t, inrange_timer);
+	struct input_dev *input = data->input_tablet;
+
+	input_report_key(input, BTN_TOOL_PEN, 0);
+	input_sync(input);
+}
+
+static int letsketch_raw_event(struct hid_device *hdev,
+			       struct hid_report *report,
+			       u8 *raw_data, int size)
+{
+	struct letsketch_data *data = hid_get_drvdata(hdev);
+	struct input_dev *input;
+	int i;
+
+	if (size != LETSKETCH_RAW_DATA_LEN || raw_data[0] != LETSKETCH_RAW_REPORT_ID)
+		return 0;
+
+	switch (raw_data[1] & 0xf0) {
+	case 0x80: /* Pen data */
+		input = data->input_tablet;
+		input_report_key(input, BTN_TOOL_PEN, 1);
+		input_report_key(input, BTN_TOUCH, raw_data[1] & 0x01);
+		input_report_key(input, BTN_STYLUS, raw_data[1] & 0x02);
+		input_report_key(input, BTN_STYLUS2, raw_data[1] & 0x04);
+		input_report_abs(input, ABS_X,
+				 get_unaligned_le16(raw_data + 2));
+		input_report_abs(input, ABS_Y,
+				 get_unaligned_le16(raw_data + 4));
+		input_report_abs(input, ABS_PRESSURE,
+				 get_unaligned_le16(raw_data + 6));
+		/*
+		 * There is no out of range event, so use a timer for this
+		 * when in range we get an event approx. every 8 ms.
+		 */
+		mod_timer(&data->inrange_timer, jiffies + msecs_to_jiffies(100));
+		break;
+	case 0xe0: /* Pad data */
+		input = data->input_tablet_pad;
+		for (i = 0; i < LETSKETCH_PAD_BUTTONS; i++)
+			input_report_key(input, BTN_0 + i, raw_data[4] == (i + 1));
+		break;
+	default:
+		hid_warn(data->hdev, "Warning unknown data header: 0x%02x\n",
+			 raw_data[0]);
+		return 0;
+	}
+
+	input_sync(input);
+	return 0;
+}
+
+/*
+ * The tablets magic handshake to put it in raw mode relies on getting
+ * string descriptors. But the firmware is buggy and does not like it if
+ * we do this too fast. Even if we go slow sometimes the usb_string() call
+ * fails. Ignore errors and retry it a couple of times if necessary.
+ */
+static int letsketch_get_string(struct usb_device *udev, int index, char *buf, int size)
+{
+	int i, ret;
+
+	for (i = 0; i < LETSKETCH_GET_STRING_RETRIES; i++) {
+		usleep_range(5000, 7000);
+		ret = usb_string(udev, index, buf, size);
+		if (ret > 0)
+			return 0;
+	}
+
+	dev_err(&udev->dev, "Max retries (%d) exceeded reading string descriptor %d\n",
+		LETSKETCH_GET_STRING_RETRIES, index);
+	return ret ? ret : -EIO;
+}
+
+static int letsketch_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	struct device *dev = &hdev->dev;
+	struct letsketch_data *data;
+	struct usb_interface *intf;
+	struct usb_device *udev;
+	char buf[256];
+	int i, ret;
+
+	if (!hid_is_using_ll_driver(hdev, &usb_hid_driver))
+		return -ENODEV;
+
+	intf = to_usb_interface(hdev->dev.parent);
+	if (intf->altsetting->desc.bInterfaceNumber != LETSKETCH_RAW_IF)
+		return -ENODEV; /* Ignore the other interfaces */
+
+	udev = interface_to_usbdev(intf);
+
+	/*
+	 * Instead of using a set-feature request, or even a custom USB ctrl
+	 * message the tablet needs this elaborate magic reading of USB
+	 * string descriptors to kick it into raw mode. This is what the
+	 * Windows drivers are seen doing in an USB trace under Windows.
+	 */
+	for (i = LETSKETCH_INFO_STR_IDX_BEGIN; i <= LETSKETCH_INFO_STR_IDX_END; i++) {
+		ret = letsketch_get_string(udev, i, buf, sizeof(buf));
+		if (ret)
+			return ret;
+
+		hid_info(hdev, "Device info: %s\n", buf);
+	}
+
+	for (i = 1; i <= 250; i++) {
+		ret = letsketch_get_string(udev, i, buf, sizeof(buf));
+		if (ret)
+			return ret;
+	}
+
+	ret = letsketch_get_string(udev, 0x64, buf, sizeof(buf));
+	if (ret)
+		return ret;
+
+	ret = letsketch_get_string(udev, LETSKETCH_INFO_STR_IDX_BEGIN, buf, sizeof(buf));
+	if (ret)
+		return ret;
+
+	/*
+	 * The tablet should be in raw mode now, end with a final delay before
+	 * doing further IO to the device.
+	 */
+	usleep_range(5000, 7000);
+
+	ret = hid_parse(hdev);
+	if (ret)
+		return ret;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->hdev = hdev;
+	timer_setup(&data->inrange_timer, letsketch_inrange_timeout, 0);
+	hid_set_drvdata(hdev, data);
+
+	ret = letsketch_setup_input_tablet(data);
+	if (ret)
+		return ret;
+
+	ret = letsketch_setup_input_tablet_pad(data);
+	if (ret)
+		return ret;
+
+	return hid_hw_start(hdev, HID_CONNECT_HIDRAW);
+}
+
+static const struct hid_device_id letsketch_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LETSKETCH, USB_DEVICE_ID_WP9620N) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, letsketch_devices);
+
+static struct hid_driver letsketch_driver = {
+	.name = "letsketch",
+	.id_table = letsketch_devices,
+	.probe = letsketch_probe,
+	.raw_event = letsketch_raw_event,
+};
+module_hid_driver(letsketch_driver);
+
+MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
+MODULE_LICENSE("GPL");