HID: uclogic: Handle wireless device reconnection

UGEEv2 tablets with battery can be connected using a USB cable or a USB
Bluetooth dongle.

When the Bluetooth dongle is used, the connection to that tablet can be
lost because the tablet is out of the range of the receiver or because
it was switched off using the switch placed in the back of the tablet's
frame.

After losing connection, the tablet is able to reconnect automatically
and its firmware sends a special packet indicating that the device was
reconnected. In response to this packet, the tablet needs to receive the
same array of magic data it expects on probe to enable its interfaces.

This patch implements a generic mechanism to hook raw events and
schedule a work to perform any custom action.

Tested-by: Mia Kanashi <[e-mail]>
Tested-by: Andreas Grosse <[e-mail]>
Signed-off-by: José Expósito <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/hid-uclogic-core-test.c

···
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ *  HID driver for UC-Logic devices not fully compliant with HID standard
+ *
+ *  Copyright (c) 2022 José Expósito <[e-mail]>
+ */
+
+#include <kunit/test.h>
+#include "./hid-uclogic-params.h"
+
+#define MAX_EVENT_SIZE 12
+
+struct uclogic_raw_event_hook_test {
+	u8 event[MAX_EVENT_SIZE];
+	size_t size;
+	bool expected;
+};
+
+static struct uclogic_raw_event_hook_test hook_events[] = {
+	{
+		.event = { 0xA1, 0xB2, 0xC3, 0xD4 },
+		.size = 4,
+	},
+	{
+		.event = { 0x1F, 0x2E, 0x3D, 0x4C, 0x5B, 0x6A },
+		.size = 6,
+	},
+};
+
+static struct uclogic_raw_event_hook_test test_events[] = {
+	{
+		.event = { 0xA1, 0xB2, 0xC3, 0xD4 },
+		.size = 4,
+		.expected = true,
+	},
+	{
+		.event = { 0x1F, 0x2E, 0x3D, 0x4C, 0x5B, 0x6A },
+		.size = 6,
+		.expected = true,
+	},
+	{
+		.event = { 0xA1, 0xB2, 0xC3 },
+		.size = 3,
+		.expected = false,
+	},
+	{
+		.event = { 0xA1, 0xB2, 0xC3, 0xD4, 0x00 },
+		.size = 5,
+		.expected = false,
+	},
+	{
+		.event = { 0x2E, 0x3D, 0x4C, 0x5B, 0x6A, 0x1F },
+		.size = 6,
+		.expected = false,
+	},
+};
+
+static void hid_test_uclogic_exec_event_hook_test(struct kunit *test)
+{
+	struct uclogic_params p = {0, };
+	struct uclogic_raw_event_hook *filter;
+	bool res;
+	int n;
+
+	/* Initialize the list of events to hook */
+	p.event_hooks = kunit_kzalloc(test, sizeof(*p.event_hooks), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, p.event_hooks);
+	INIT_LIST_HEAD(&p.event_hooks->list);
+
+	for (n = 0; n < ARRAY_SIZE(hook_events); n++) {
+		filter = kunit_kzalloc(test, sizeof(*filter), GFP_KERNEL);
+		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, filter);
+
+		filter->size = hook_events[n].size;
+		filter->event = kunit_kzalloc(test, filter->size, GFP_KERNEL);
+		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, filter->event);
+		memcpy(filter->event, &hook_events[n].event[0], filter->size);
+
+		list_add_tail(&filter->list, &p.event_hooks->list);
+	}
+
+	/* Test uclogic_exec_event_hook() */
+	for (n = 0; n < ARRAY_SIZE(test_events); n++) {
+		res = uclogic_exec_event_hook(&p, &test_events[n].event[0],
+					      test_events[n].size);
+		KUNIT_ASSERT_EQ(test, res, test_events[n].expected);
+	}
+}
+
+static struct kunit_case hid_uclogic_core_test_cases[] = {
+	KUNIT_CASE(hid_test_uclogic_exec_event_hook_test),
+	{}
+};
+
+static struct kunit_suite hid_uclogic_core_test_suite = {
+	.name = "hid_uclogic_core_test",
+	.test_cases = hid_uclogic_core_test_cases,
+};
+
+kunit_test_suite(hid_uclogic_core_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for the UC-Logic driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("José Expósito <[e-mail]>");

drivers/hid/hid-uclogic-core.c

···
 #endif
 
 /**
+ * uclogic_exec_event_hook - if the received event is hooked schedules the
+ * associated work.
+ *
+ * @p:		Tablet interface report parameters.
+ * @event:	Raw event.
+ * @size:	The size of event.
+ *
+ * Returns:
+ *	Whether the event was hooked or not.
+ */
+static bool uclogic_exec_event_hook(struct uclogic_params *p, u8 *event, int size)
+{
+	struct uclogic_raw_event_hook *curr;
+
+	if (!p->event_hooks)
+		return false;
+
+	list_for_each_entry(curr, &p->event_hooks->list, list) {
+		if (curr->size == size && memcmp(curr->event, event, size) == 0) {
+			schedule_work(&curr->work);
+			return true;
+		}
+	}
+
+	return false;
+}
+
+/**
  * uclogic_raw_event_pen - handle raw pen events (pen HID reports).
  *
  * @drvdata:	Driver data.
···
 	if (report->type != HID_INPUT_REPORT)
 		return 0;
 
+	if (uclogic_exec_event_hook(params, data, size))
+		return 0;
+
 	while (true) {
 		/* Tweak pen reports, if necessary */
 		if ((report_id == params->pen.id) && (size >= 2)) {
···
 MODULE_AUTHOR("Martin Rusko");
 MODULE_AUTHOR("Nikolai Kondrashov");
 MODULE_LICENSE("GPL");
+
+#ifdef CONFIG_HID_KUNIT_TEST
+#include "hid-uclogic-core-test.c"
+#endif

drivers/hid/hid-uclogic-params-test.c

···
 	KUNIT_EXPECT_EQ(test, params->frame_type, frame_type);
 }
 
+static void hid_test_uclogic_params_cleanup_event_hooks(struct kunit *test)
+{
+	int res, n;
+	struct uclogic_params p = {0, };
+
+	res = uclogic_params_ugee_v2_init_event_hooks(NULL, &p);
+	KUNIT_ASSERT_EQ(test, res, 0);
+
+	/* Check that the function can be called repeatedly */
+	for (n = 0; n < 4; n++) {
+		uclogic_params_cleanup_event_hooks(&p);
+		KUNIT_EXPECT_PTR_EQ(test, p.event_hooks, NULL);
+	}
+}
+
 static struct kunit_case hid_uclogic_params_test_cases[] = {
 	KUNIT_CASE_PARAM(hid_test_uclogic_parse_ugee_v2_desc,
 			 uclogic_parse_ugee_v2_desc_gen_params),
+	KUNIT_CASE(hid_test_uclogic_params_cleanup_event_hooks),
 	{}
 };
 

drivers/hid/hid-uclogic-params.c

···
 }
 
 /**
+ * uclogic_params_cleanup_event_hooks - free resources used by the list of raw
+ * event hooks.
+ * Can be called repeatedly.
+ *
+ * @params: Input parameters to cleanup. Cannot be NULL.
+ */
+static void uclogic_params_cleanup_event_hooks(struct uclogic_params *params)
+{
+	struct uclogic_raw_event_hook *curr, *n;
+
+	if (!params || !params->event_hooks)
+		return;
+
+	list_for_each_entry_safe(curr, n, &params->event_hooks->list, list) {
+		cancel_work_sync(&curr->work);
+		list_del(&curr->list);
+		kfree(curr->event);
+		kfree(curr);
+	}
+
+	kfree(params->event_hooks);
+	params->event_hooks = NULL;
+}
+
+/**
  * uclogic_params_cleanup - free resources used by struct uclogic_params
  * (tablet interface's parameters).
  * Can be called repeatedly.
···
 		for (i = 0; i < ARRAY_SIZE(params->frame_list); i++)
 			uclogic_params_frame_cleanup(&params->frame_list[i]);
 
+		uclogic_params_cleanup_event_hooks(params);
 		memset(params, 0, sizeof(*params));
 	}
 }
···
 }
 
 /**
+ * uclogic_params_ugee_v2_reconnect_work() - When a wireless tablet looses
+ * connection to the USB dongle and reconnects, either because of its physical
+ * distance or because it was switches off and on using the frame's switch,
+ * uclogic_probe_interface() needs to be called again to enable the tablet.
+ *
+ * @work: The work that triggered this function.
+ */
+static void uclogic_params_ugee_v2_reconnect_work(struct work_struct *work)
+{
+	struct uclogic_raw_event_hook *event_hook;
+
+	event_hook = container_of(work, struct uclogic_raw_event_hook, work);
+	uclogic_probe_interface(event_hook->hdev, uclogic_ugee_v2_probe_arr,
+				uclogic_ugee_v2_probe_size,
+				uclogic_ugee_v2_probe_endpoint);
+}
+
+/**
+ * uclogic_params_ugee_v2_init_event_hooks() - initialize the list of events
+ * to be hooked for UGEE v2 devices.
+ * @hdev:	The HID device of the tablet interface to initialize and get
+ *		parameters from.
+ * @p:		Parameters to fill in, cannot be NULL.
+ *
+ * Returns:
+ *	Zero, if successful. A negative errno code on error.
+ */
+static int uclogic_params_ugee_v2_init_event_hooks(struct hid_device *hdev,
+						   struct uclogic_params *p)
+{
+	struct uclogic_raw_event_hook *event_hook;
+	__u8 reconnect_event[] = {
+		/* Event received on wireless tablet reconnection */
+		0x02, 0xF8, 0x02, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+	};
+
+	if (!p)
+		return -EINVAL;
+
+	/* The reconnection event is only received if the tablet has battery */
+	if (!uclogic_params_ugee_v2_has_battery(hdev))
+		return 0;
+
+	p->event_hooks = kzalloc(sizeof(*p->event_hooks), GFP_KERNEL);
+	if (!p->event_hooks)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&p->event_hooks->list);
+
+	event_hook = kzalloc(sizeof(*event_hook), GFP_KERNEL);
+	if (!event_hook)
+		return -ENOMEM;
+
+	INIT_WORK(&event_hook->work, uclogic_params_ugee_v2_reconnect_work);
+	event_hook->hdev = hdev;
+	event_hook->size = ARRAY_SIZE(reconnect_event);
+	event_hook->event = kmemdup(reconnect_event, event_hook->size, GFP_KERNEL);
+	if (!event_hook->event)
+		return -ENOMEM;
+
+	list_add_tail(&event_hook->list, &p->event_hooks->list);
+
+	return 0;
+}
+
+/**
  * uclogic_params_ugee_v2_init() - initialize a UGEE graphics tablets by
  * discovering their parameters.
  *
···
 			hid_err(hdev, "error initializing battery: %d\n", rc);
 			goto cleanup;
 		}
+	}
+
+	/* Create a list of raw events to be ignored */
+	rc = uclogic_params_ugee_v2_init_event_hooks(hdev, &p);
+	if (rc) {
+		hid_err(hdev, "error initializing event hook list: %d\n", rc);
+		goto cleanup;
 	}
 
 output:

drivers/hid/hid-uclogic-params.h

···
 
 #include <linux/usb.h>
 #include <linux/hid.h>
+#include <linux/list.h>
 
 #define UCLOGIC_MOUSE_FRAME_QUIRK	BIT(0)
 #define UCLOGIC_BATTERY_QUIRK		BIT(1)
···
 };
 
 /*
+ * List of works to be performed when a certain raw event is received.
+ */
+struct uclogic_raw_event_hook {
+	struct hid_device *hdev;
+	__u8 *event;
+	size_t size;
+	struct work_struct work;
+	struct list_head list;
+};
+
+/*
  * Tablet interface report parameters.
  *
  * Must use declarative (descriptive) language, not imperative, to simplify
···
 	 * parts. Only valid, if "invalid" is false.
 	 */
 	struct uclogic_params_frame frame_list[3];
+	/*
+	 * List of event hooks.
+	 */
+	struct uclogic_raw_event_hook *event_hooks;
 };
 
 /* Driver data */