[PATCH v3] Drivers: input: misc: Add driver touchscreen-buttons to support physically labeled buttons on touch screen surfaces

[PATCH v3] Drivers: input: misc: Add driver touchscreen-buttons to support physically labeled buttons on touch screen surfaces

[Carl Philipp Klemm]

Adds a driver for supporting permanet, physically labeled, buttons on
touchscreen surfaces. As are common on android phones designed with android 1.0
to 2.3 in mind. The driver works by attaching to another input device and
mirroring its events, while inserting key events and filtering for touches that
land on the buttons. Buttons are arbitrary rectangles configurable via dts.

Signed-off-by: Carl Philipp Klemm <philipp@uvos.xyz>
---

Changes since v2:
- Decrease the potential for memory leaks by migrating to devm_* where possible

---
 drivers/input/misc/Kconfig               |   8 +
 drivers/input/misc/Makefile              |   1 +
 drivers/input/misc/touchscreen-buttons.c | 587 +++++++++++++++++++++++
 3 files changed, 596 insertions(+)
 create mode 100644 drivers/input/misc/touchscreen-buttons.c

diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index 362e8a01980c..3d487b8e7d8b 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -318,6 +318,14 @@ config INPUT_CPCAP_PWRBUTTON
 	  To compile this driver as a module, choose M here. The module will
 	  be called cpcap-pwrbutton.
 
+config INPUT_TOUCHSCREEN_BUTTONS
+	tristate "Touchscreen Buttons"
+	help
+	  Say Y here if you want to enable buttons on touchscreen devices.
+
+	  To compile this driver as a module, choose M here. The module will
+	  be called touchscreen-buttons.
+
 config INPUT_WISTRON_BTNS
 	tristate "x86 Wistron laptop button interface"
 	depends on X86_32
diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
index a48e5f2d859d..18032a1b2a9c 100644
--- a/drivers/input/misc/Makefile
+++ b/drivers/input/misc/Makefile
@@ -84,4 +84,5 @@ obj-$(CONFIG_INPUT_WM831X_ON)		+= wm831x-on.o
 obj-$(CONFIG_INPUT_XEN_KBDDEV_FRONTEND)	+= xen-kbdfront.o
 obj-$(CONFIG_INPUT_YEALINK)		+= yealink.o
 obj-$(CONFIG_INPUT_IDEAPAD_SLIDEBAR)	+= ideapad_slidebar.o
+obj-$(CONFIG_INPUT_TOUCHSCREEN_BUTTONS)	+= touchscreen-buttons.o
 
diff --git a/drivers/input/misc/touchscreen-buttons.c b/drivers/input/misc/touchscreen-buttons.c
new file mode 100644
index 000000000000..45602a23e2ac
--- /dev/null
+++ b/drivers/input/misc/touchscreen-buttons.c
@@ -0,0 +1,587 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/**
+ * Touchscreen Virutal Button Input Driver
+ *
+ * Copyright (C) 2020 Carl Klemm <carl@uvos.xyz>
+ *
+ * This file is subject to the terms and conditions of the GNU General
+ * Public License. See the file "COPYING" in the main directory of this
+ * archive for more details.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/platform_device.h>
+#include <linux/errno.h>
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/input/mt.h>
+#include <linux/device/bus.h>
+#include <linux/string.h>
+#include <linux/workqueue.h>
+
+#define EVENT_QUEUE_SIZE 32
+
+struct touchscreen_button {
+	u32 x;
+	u32 y;
+	u32 width;
+	u32 height;
+	u32 keycode;
+	u8 depressed;
+};
+
+struct touchscreen_button_map {
+	struct touchscreen_button *buttons;
+	u32 count;
+	struct device_node *ts_node;
+};
+
+struct event {
+	unsigned int type;
+	unsigned int code;
+	int value;
+};
+
+struct event_queue {
+	struct event events[EVENT_QUEUE_SIZE];
+	unsigned int lastindex;
+};
+
+struct touchscreen_buttons {
+	struct device *dev;
+	struct input_dev *buttons_idev;
+	struct input_dev *filtered_ts_idev;
+	struct touchscreen_button_map *map;
+	struct input_handler *handler;
+	struct input_handle *ts_handle;
+	struct event_queue queue;
+	struct workqueue_struct *workqueue;
+	struct work_struct open_task;
+	struct work_struct close_task;
+	struct work_struct merge_task;
+	struct mutex mutex;
+};
+
+static const struct input_device_id touchscreen_buttons_ids[] = {
+	{
+	 .flags = INPUT_DEVICE_ID_MATCH_EVBIT,
+	 .evbit = {BIT_MASK(EV_ABS)},
+	 },
+	{
+	 .flags = INPUT_DEVICE_ID_MATCH_EVBIT,
+	 .evbit = {BIT_MASK(EV_KEY)},
+	 },
+	{
+	 .flags = INPUT_DEVICE_ID_MATCH_EVBIT,
+	 .evbit = {BIT_MASK(EV_SYN)},
+	 },
+	{},
+};
+
+static int touchscreen_buttons_process_syn(const struct event_queue *queue,
+					   const struct touchscreen_button_map
+					   *map, struct input_dev *idev)
+{
+	u32 i;
+	int x, y, ret, pressed;
+
+	x = INT_MIN;
+	y = INT_MIN;
+	pressed = -1;
+	ret = 0;
+
+	for (i = 0; i < queue->lastindex; ++i) {
+		const struct event *ev;
+
+		ev = &queue->events[i];
+		if (ev->type == EV_ABS && ev->code == ABS_X)
+			x = ev->value;
+		else if (ev->type == EV_ABS && ev->code == ABS_Y)
+			y = ev->value;
+		else if (ev->type == EV_KEY && ev->code == BTN_TOUCH)
+			pressed = ev->value;
+	}
+
+	for (i = 0; i < map->count; ++i) {
+		struct touchscreen_button *button = &map->buttons[i];
+
+		if (pressed == 1 &&
+		    button->x <= x &&
+		    button->y <= y &&
+		    button->width + button->x >= x &&
+		    button->height + button->y >= y && button->depressed == 0) {
+			input_report_key(idev, button->keycode, 1);
+			button->depressed = 1;
+			ret = 1;
+		} else if (button->depressed == 1) {
+			if (pressed == 0) {
+				input_report_key(idev, button->keycode, 0);
+				button->depressed = 0;
+			}
+			ret = 2;
+		}
+	}
+
+	if (ret != 0) {
+		input_event(idev, EV_SYN, SYN_REPORT, 0);
+	} else if (ret == 0) {
+		bool buttonpressed = false;
+
+		for (i = 0; i < map->count; ++i)
+			buttonpressed = buttonpressed
+			    || map->buttons[i].depressed;
+		if (buttonpressed)
+			ret = 3;
+	}
+
+	return ret;
+}
+
+static void touchscreen_buttons_resend_events(const struct event_queue *queue,
+					      struct input_dev *idev)
+{
+	u32 i;
+
+	for (i = 0; i < queue->lastindex; ++i)
+		input_event(idev, queue->events[i].type, queue->events[i].code,
+			    queue->events[i].value);
+	input_event(idev, EV_SYN, SYN_REPORT, 0);
+}
+
+static void touchscreen_buttons_copy_mt_slots(struct input_dev *target,
+					      struct input_dev *source)
+{
+	if (source->mt && target->mt
+	    && source->mt->num_slots == target->mt->num_slots) {
+		memcpy(target->mt->slots, source->mt->slots,
+		       sizeof(struct input_mt_slot) * source->mt->num_slots);
+	}
+}
+
+static void touchscreen_buttons_input_event(struct input_handle *handle,
+					    unsigned int type,
+					    unsigned int code, int value)
+{
+	struct touchscreen_buttons *buttons;
+
+	buttons = handle->private;
+
+	if (type == EV_SYN && code == SYN_REPORT) {
+		if (touchscreen_buttons_process_syn(&buttons->queue,
+						    buttons->map,
+						    buttons->buttons_idev) == 0)
+			touchscreen_buttons_resend_events(&buttons->queue,
+							  buttons->filtered_ts_idev);
+		buttons->queue.lastindex = 0;
+	} else if (buttons->queue.lastindex < EVENT_QUEUE_SIZE) {
+		buttons->queue.events[buttons->queue.lastindex].type = type;
+		buttons->queue.events[buttons->queue.lastindex].code = code;
+		buttons->queue.events[buttons->queue.lastindex].value = value;
+		++buttons->queue.lastindex;
+	} else {
+		dev_warn(buttons->dev,
+			 "event_qeue overrun, will not capture events until next SYN_REPORT\n");
+	}
+}
+
+static void touchscreen_buttons_merge_capabilitys(struct input_dev *target,
+						  struct input_dev *source)
+{
+	unsigned int i;
+
+	mutex_lock(&target->mutex);
+	mutex_lock(&source->mutex);
+	for (i = 0; i < BITS_TO_LONGS(INPUT_PROP_CNT); ++i)
+		target->propbit[i] = target->propbit[i] | source->propbit[i];
+	for (i = 0; i < BITS_TO_LONGS(EV_CNT); ++i)
+		target->evbit[i] = target->evbit[i] | source->evbit[i];
+	for (i = 0; i < BITS_TO_LONGS(KEY_CNT); ++i)
+		target->keybit[i] = target->keybit[i] | source->keybit[i];
+	for (i = 0; i < BITS_TO_LONGS(REL_CNT); ++i)
+		target->relbit[i] = target->relbit[i] | source->relbit[i];
+	for (i = 0; i < BITS_TO_LONGS(ABS_CNT); ++i)
+		target->absbit[i] = target->absbit[i] | source->absbit[i];
+	for (i = 0; i < BITS_TO_LONGS(MSC_CNT); ++i)
+		target->mscbit[i] = target->mscbit[i] | source->mscbit[i];
+	for (i = 0; i < BITS_TO_LONGS(LED_CNT); ++i)
+		target->ledbit[i] = target->ledbit[i] | source->ledbit[i];
+	for (i = 0; i < BITS_TO_LONGS(SND_CNT); ++i)
+		target->sndbit[i] = target->sndbit[i] | source->sndbit[i];
+	for (i = 0; i < BITS_TO_LONGS(FF_CNT); ++i)
+		target->ffbit[i] = target->ffbit[i] | source->ffbit[i];
+	for (i = 0; i < BITS_TO_LONGS(SW_CNT); ++i)
+		target->swbit[i] = target->swbit[i] | source->swbit[i];
+	mutex_unlock(&source->mutex);
+	mutex_unlock(&target->mutex);
+
+	if (*source->evbit & (1 << EV_ABS)) {
+		input_alloc_absinfo(target);
+		mutex_lock(&target->mutex);
+		mutex_lock(&source->mutex);
+		for (i = 0; i < ABS_CNT; ++i)
+			target->absinfo[i] = source->absinfo[i];
+		mutex_unlock(&source->mutex);
+		mutex_unlock(&target->mutex);
+		if (source->mt) {
+			input_mt_init_slots(target, source->mt->num_slots,
+					    source->mt->flags);
+			mutex_lock(&target->mutex);
+			mutex_lock(&source->mutex);
+			touchscreen_buttons_copy_mt_slots(target, source);
+			mutex_unlock(&source->mutex);
+			mutex_unlock(&target->mutex);
+		}
+	}
+}
+
+static void merge_task_handler(struct work_struct *work)
+{
+	struct touchscreen_buttons *buttons =
+	    container_of(work, struct touchscreen_buttons, merge_task);
+
+
+	mutex_lock(&buttons->mutex);
+	if (buttons->ts_handle && buttons->ts_handle->dev)
+		touchscreen_buttons_merge_capabilitys(buttons->filtered_ts_idev,
+						      buttons->ts_handle->dev);
+	mutex_unlock(&buttons->mutex);
+}
+
+static void close_task_handler(struct work_struct *work)
+{
+	struct touchscreen_buttons *buttons =
+	    container_of(work, struct touchscreen_buttons, close_task);
+
+	mutex_lock(&buttons->mutex);
+	if (buttons && buttons->ts_handle && buttons->ts_handle->open != 0)
+		input_close_device(buttons->ts_handle);
+	mutex_unlock(&buttons->mutex);
+}
+
+static void open_task_handler(struct work_struct *work)
+{
+	struct touchscreen_buttons *buttons =
+	    container_of(work, struct touchscreen_buttons, open_task);
+	int error;
+
+	mutex_lock(&buttons->mutex);
+	if (buttons && buttons->ts_handle) {
+		error = input_open_device(buttons->ts_handle);
+		if (error) {
+			dev_err(buttons->dev,
+				"Failed to open input device, error %d\n",
+				error);
+			input_unregister_handle(buttons->ts_handle);
+			kfree(buttons->ts_handle);
+			buttons->ts_handle = NULL;
+		}
+	}
+	mutex_unlock(&buttons->mutex);
+}
+
+static int touchscreen_buttons_input_connect(struct input_handler *handler,
+					     struct input_dev *dev,
+					     const struct input_device_id *id)
+{
+	struct touchscreen_buttons *buttons;
+
+	buttons = handler->private;
+
+	mutex_lock(&buttons->mutex);
+
+	if ((!buttons->ts_handle
+	     && device_match_of_node(&dev->dev, buttons->map->ts_node))
+	    || (dev->dev.parent
+		&& device_match_of_node(dev->dev.parent,
+					buttons->map->ts_node))) {
+		int error;
+
+		dev_info(buttons->dev, "Binding to device: %s\n",
+			 dev_name(&dev->dev));
+
+		buttons->ts_handle =
+		    kzalloc(sizeof(*buttons->ts_handle), GFP_KERNEL);
+		if (!buttons->ts_handle) {
+			mutex_unlock(&buttons->mutex);
+			return -ENOMEM;
+		}
+
+		buttons->ts_handle->dev = dev;
+		buttons->ts_handle->handler = handler;
+		buttons->ts_handle->name = "touchscreen-buttons";
+		buttons->ts_handle->private = handler->private;
+		buttons->queue.lastindex = 0;
+
+		error = input_register_handle(buttons->ts_handle);
+		if (error) {
+			dev_err(buttons->dev,
+				"Failed to register input handler, error %d\n",
+				error);
+			kfree(buttons->ts_handle);
+			buttons->ts_handle = NULL;
+			mutex_unlock(&buttons->mutex);
+			return error;
+		}
+
+		queue_work(buttons->workqueue, &buttons->merge_task);
+
+		if (buttons->filtered_ts_idev->users > 0
+		    && buttons->ts_handle->open == 0)
+			queue_work(buttons->workqueue, &buttons->open_task);
+	}
+
+	mutex_unlock(&buttons->mutex);
+	return 0;
+}
+
+static void touchscreen_buttons_input_disconnect(struct input_handle *handle)
+{
+	struct touchscreen_buttons *buttons;
+
+	buttons = handle->private;
+
+	mutex_lock(&buttons->mutex);
+	if (handle == buttons->ts_handle) {
+		input_close_device(handle);
+		input_unregister_handle(handle);
+		kfree(handle);
+		buttons->ts_handle = NULL;
+		dev_info(buttons->dev,
+			 "Touchscreen device disconnected buttons disabled\n");
+	} else {
+		dev_err(buttons->dev,
+			"Unknown device disconnected, %p should be %p", handle,
+			buttons->ts_handle);
+	}
+	mutex_unlock(&buttons->mutex);
+}
+
+static struct touchscreen_button_map
+*touchscreen_buttons_get_devtree_pdata(struct device *dev)
+{
+	struct touchscreen_button_map *map;
+	struct fwnode_handle *child_node;
+	struct device_node *node;
+	int i;
+
+	map = devm_kzalloc(dev, sizeof(*map), GFP_KERNEL);
+	if (!map)
+		return ERR_PTR(-ENOMEM);
+
+	map->count = device_get_child_node_count(dev);
+	if (map->count == 0)
+		return ERR_PTR(-ENODEV);
+
+	map->buttons = devm_kcalloc(dev, map->count, sizeof(*map->buttons), GFP_KERNEL);
+	if (!map->buttons)
+		return ERR_PTR(-ENOMEM);
+
+	node = dev->of_node;
+	map->ts_node = of_parse_phandle(node, "touchscreen_phandle", 0);
+	if (!map->ts_node) {
+		dev_err(dev, "touchscreen_phandle node missing\n");
+		return ERR_PTR(-ENODEV);
+	}
+
+	dev_info(dev, "Device_node name: %s\n", map->ts_node->name);
+
+	i = 0;
+	device_for_each_child_node(dev, child_node) {
+		struct touchscreen_button *button;
+
+		button = &map->buttons[i];
+
+		fwnode_property_read_u32(child_node, "x-position", &button->x);
+		fwnode_property_read_u32(child_node, "y-position", &button->y);
+		fwnode_property_read_u32(child_node, "x-size", &button->width);
+		fwnode_property_read_u32(child_node, "y-size", &button->height);
+		fwnode_property_read_u32(child_node, "keycode",
+					 &button->keycode);
+		dev_info(dev,
+			 "Adding button at x=%u y=%u size %u x %u keycode=%u\n",
+			 button->x, button->y, button->width, button->height,
+			 button->keycode);
+		++i;
+	}
+	return map;
+}
+
+static int touchscreen_buttons_idev_opened(struct input_dev *idev)
+{
+	struct touchscreen_buttons *buttons;
+
+	buttons = dev_get_drvdata(idev->dev.parent);
+
+	mutex_lock(&buttons->mutex);
+	if (buttons && buttons->ts_handle) {
+		if (buttons->ts_handle->open == 0) {
+			queue_work(buttons->workqueue, &buttons->open_task);
+			dev_dbg(idev->dev.parent, "idev opened\n");
+		} else {
+			dev_info(idev->dev.parent, "idev allready opened\n");
+		}
+	} else {
+		dev_warn(idev->dev.parent,
+			 "Input device opend but touchscreen not opened. %p %p\n",
+			 buttons, buttons->ts_handle);
+	}
+	mutex_unlock(&buttons->mutex);
+	return 0;
+}
+
+static void touchscreen_buttons_idev_closed(struct input_dev *idev)
+{
+	struct touchscreen_buttons *buttons;
+
+	buttons = dev_get_drvdata(idev->dev.parent);
+
+	mutex_lock(&buttons->mutex);
+	if (buttons && buttons->ts_handle && buttons->ts_handle->open != 0) {
+		queue_work(buttons->workqueue, &buttons->close_task);
+		dev_dbg(idev->dev.parent, "idev closed\n");
+	}
+	mutex_unlock(&buttons->mutex);
+}
+
+static int touchscreen_buttons_probe(struct platform_device *pdev)
+{
+	struct touchscreen_buttons *buttons;
+	int error, i;
+
+	buttons = devm_kzalloc(&pdev->dev, sizeof(*buttons), GFP_KERNEL);
+	if (!buttons)
+		return -ENOMEM;
+
+	dev_set_drvdata(&pdev->dev, buttons);
+
+	buttons->workqueue =
+	    create_singlethread_workqueue("touchscreen-buttons-workqueue");
+	INIT_WORK(&buttons->merge_task, merge_task_handler);
+	INIT_WORK(&buttons->open_task, open_task_handler);
+	INIT_WORK(&buttons->close_task, close_task_handler);
+
+	mutex_init(&buttons->mutex);
+
+	buttons->queue.lastindex = 0;
+	buttons->dev = &pdev->dev;
+
+	buttons->map = touchscreen_buttons_get_devtree_pdata(&pdev->dev);
+	if (IS_ERR(buttons->map))
+		return PTR_ERR(buttons->map);
+
+	/*filtered touchscreen device */
+	buttons->filtered_ts_idev = input_allocate_device();
+	if (!buttons->filtered_ts_idev)
+		return -ENOMEM;
+	buttons->filtered_ts_idev->name = "Filtered Touchscreen";
+	buttons->filtered_ts_idev->phys = "touchscreen-buttons/input1";
+	buttons->filtered_ts_idev->dev.parent = buttons->dev;
+	buttons->filtered_ts_idev->open = touchscreen_buttons_idev_opened;
+	buttons->filtered_ts_idev->close = touchscreen_buttons_idev_closed;
+
+	/*buttons input device */
+	buttons->buttons_idev = input_allocate_device();
+	if (!buttons->buttons_idev)
+		return -ENOMEM;
+	buttons->buttons_idev->name = "Touchscreen Buttons";
+	buttons->buttons_idev->phys = "touchscreen-buttons/input0";
+	buttons->buttons_idev->dev.parent = buttons->dev;
+	for (i = 0; i < buttons->map->count; ++i)
+		input_set_capability(buttons->buttons_idev, EV_KEY,
+				     buttons->map->buttons[i].keycode);
+
+	/*handler for touchscreen input device */
+	buttons->handler = devm_kzalloc(&pdev->dev, sizeof(*buttons->handler), GFP_KERNEL);
+
+	buttons->handler->event = touchscreen_buttons_input_event;
+	buttons->handler->connect = touchscreen_buttons_input_connect;
+	buttons->handler->disconnect = touchscreen_buttons_input_disconnect;
+	buttons->handler->name = "touchscreen-buttons";
+	buttons->handler->id_table = touchscreen_buttons_ids;
+	buttons->handler->private = buttons;
+
+	error = input_register_handler(buttons->handler);
+	if (error) {
+		dev_err(&pdev->dev, "Input handler register failed: %d\n",
+			error);
+		return error;
+	}
+
+	error = input_register_device(buttons->buttons_idev);
+	if (error) {
+		dev_err(&pdev->dev, "Input device register failed: %d\n",
+			error);
+		return error;
+	}
+
+	error = input_register_device(buttons->filtered_ts_idev);
+	if (error) {
+		dev_err(&pdev->dev, "Input device register failed: %d\n",
+			error);
+		return error;
+	}
+
+	return 0;
+}
+
+static int touchscreen_buttons_remove(struct platform_device *pdev)
+{
+	struct touchscreen_buttons *buttons = dev_get_drvdata(&pdev->dev);
+	struct input_handle *ts_handle = buttons->ts_handle;
+
+	input_unregister_device(buttons->buttons_idev);
+	input_unregister_device(buttons->filtered_ts_idev);
+
+	mutex_lock(&buttons->mutex);
+	if (buttons->ts_handle) {
+		if (buttons->ts_handle->open != 0)
+			input_close_device(buttons->ts_handle);
+		input_unregister_handle(buttons->ts_handle);
+		buttons->ts_handle = NULL;
+	}
+	mutex_unlock(&buttons->mutex);
+	input_unregister_handler(buttons->handler);
+
+	flush_workqueue(buttons->workqueue);
+	destroy_workqueue(buttons->workqueue);
+
+	kfree(ts_handle);
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id touchscreen_buttons_dt_match_table[] = {
+	{.compatible = "touchscreen-buttons"},
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, touchscreen_buttons_dt_match_table);
+#endif
+
+static struct platform_driver touchscreen_buttons_driver = {
+	.probe = touchscreen_buttons_probe,
+	.remove = touchscreen_buttons_remove,
+	.driver = {
+		   .name = "touchscreen-buttons",
+		   .of_match_table =
+		   of_match_ptr(touchscreen_buttons_dt_match_table),
+		   },
+};
+
+module_platform_driver(touchscreen_buttons_driver);
+
+MODULE_ALIAS("platform:touchscreen-buttons");
+MODULE_DESCRIPTION("touchscreen-buttons");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Carl Klemm <carl@uvos.xyz>");
-- 
2.29.1