[PATCH v5 2/2] input: add driver for Hynitron CST816X touchscreen

From: Oleh Kuzhylnyi
Date: Sun Sep 08 2024 - 07:30:59 EST

Introduce support for the Hynitron CST816X touchscreen controller
used for 240×240 1.28-inch Round LCD Display Module manufactured
by Waveshare Electronics. The driver is designed based on an Arduino
implementation marked as under MIT License. This driver is written
for a particular round display based on the CST816S controller, which
is not compatiable with existing driver for Hynitron controllers.

Signed-off-by: Oleh Kuzhylnyi <kuzhylol@xxxxxxxxx>
---

Changes in v5:
- Update commit based on Dmitry's feedback:
- Make GPIO reset optional
- Combine declaration and initialization for i2c_xfer
- Return 0 explicitly where possible
- Rename rc (return code) to error
- Make Touch processing call return boolean
- Improve error handling for i2c_transfer
- Use get_unaligned_be16 for getting coordinates
- Move touch event completeness upper to irq callback

Changes in v4:
- Update commit based on Dmitry's feedback:
- Move abs_x and abs_y to u16
- Remove __packed qualifier for touch_info struct
- Hide tiny touch irq context to stack
- Extend cst816x_i2c_read_register() with buf and buf_size
- Remove loop from event lookup

Changes in v3:
- Drop timer and delayed work
- Process touch in threaded IRQ context
- Fix chip reset sequence
- Move input_register() before devm_request_threaded_irq()
- Re-arrange and document input reporting
- Set u16 data type for event_code
- Remove double tap event to prevent continuous double side sliding

Changes in v2:
- Apply dev_err_probe() for better error handling
- Remove redundant printing, remove dev_warn() message spamming
- Get rid of PM since the touchscreen goes into sleep mode automatically
- Get rid of IRQ control and IRQF_NO_AUTOEN flag
- Reduce timer timeout up to 10ms to handle touch events faster
- Skip registering of non-gesture CST816X_SWIPE event
- Shift input_register_device() as a final call in probe() callback
- Specify name of i2c_device_id explicitly
- Update module description and fix typo
- Add necessary spaces between lines

drivers/input/touchscreen/Kconfig | 12 +
drivers/input/touchscreen/Makefile | 1 +
drivers/input/touchscreen/hynitron-cst816x.c | 259 +++++++++++++++++++
3 files changed, 272 insertions(+)
create mode 100644 drivers/input/touchscreen/hynitron-cst816x.c

diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
index c821fe3ee794..02f40d0fbac0 100644
--- a/drivers/input/touchscreen/Kconfig
+++ b/drivers/input/touchscreen/Kconfig
@@ -481,6 +481,18 @@ config TOUCHSCREEN_HYNITRON_CSTXXX
To compile this driver as a module, choose M here: the
module will be called hynitron-cstxxx.

+config TOUCHSCREEN_HYNITRON_CST816X
+ tristate "Hynitron CST816X touchscreen support"
+ depends on I2C
+ help
+ Say Y here if you have a touchscreen using a Hynitron
+ CST816X touchscreen controller.
+
+ If unsure, say N.
+
+ To compile this driver as a module, choose M here: the
+ module will be called hynitron-cst816x.
+
config TOUCHSCREEN_ILI210X
tristate "Ilitek ILI210X based touchscreen"
depends on I2C
diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
index a81cb5aa21a5..a92a87417a97 100644
--- a/drivers/input/touchscreen/Makefile
+++ b/drivers/input/touchscreen/Makefile
@@ -51,6 +51,7 @@ obj-$(CONFIG_TOUCHSCREEN_GOODIX_BERLIN_CORE) += goodix_berlin_core.o
obj-$(CONFIG_TOUCHSCREEN_GOODIX_BERLIN_I2C) += goodix_berlin_i2c.o
obj-$(CONFIG_TOUCHSCREEN_GOODIX_BERLIN_SPI) += goodix_berlin_spi.o
obj-$(CONFIG_TOUCHSCREEN_HIDEEP) += hideep.o
+obj-$(CONFIG_TOUCHSCREEN_HYNITRON_CST816X) += hynitron-cst816x.o
obj-$(CONFIG_TOUCHSCREEN_HYNITRON_CSTXXX) += hynitron_cstxxx.o
obj-$(CONFIG_TOUCHSCREEN_ILI210X) += ili210x.o
obj-$(CONFIG_TOUCHSCREEN_ILITEK) += ilitek_ts_i2c.o
diff --git a/drivers/input/touchscreen/hynitron-cst816x.c b/drivers/input/touchscreen/hynitron-cst816x.c
new file mode 100644
index 000000000000..3886617e6a71
--- /dev/null
+++ b/drivers/input/touchscreen/hynitron-cst816x.c
@@ -0,0 +1,259 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for I2C connected Hynitron CST816X Touchscreen
+ *
+ * Copyright (C) 2024 Oleh Kuzhylnyi <kuzhylol@xxxxxxxxx>
+ */
+#include <asm/unaligned.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+
+enum cst816x_registers {
+ CST816X_FRAME = 0x01,
+ CST816X_MOTION = 0xEC,
+};
+
+enum cst816x_gestures {
+ CST816X_SWIPE_UP = 0x01,
+ CST816X_SWIPE_DOWN = 0x02,
+ CST816X_SWIPE_LEFT = 0x03,
+ CST816X_SWIPE_RIGHT = 0x04,
+ CST816X_SINGLE_TAP = 0x05,
+ CST816X_LONG_PRESS = 0x0C,
+ CST816X_RESERVED = 0xFF,
+};
+
+struct cst816x_touch_info {
+ u8 gesture;
+ u8 touch;
+ u16 abs_x;
+ u16 abs_y;
+};
+
+struct cst816x_priv {
+ struct device *dev;
+ struct i2c_client *client;
+ struct gpio_desc *reset;
+ struct input_dev *input;
+};
+
+struct cst816x_event_mapping {
+ enum cst816x_gestures gesture;
+ u16 code;
+};
+
+static const struct cst816x_event_mapping event_map[16] = {
+ {CST816X_SWIPE_UP, BTN_FORWARD},
+ {CST816X_SWIPE_DOWN, BTN_BACK},
+ {CST816X_SWIPE_LEFT, BTN_LEFT},
+ {CST816X_SWIPE_RIGHT, BTN_RIGHT},
+ {CST816X_SINGLE_TAP, BTN_TOUCH},
+ {CST816X_LONG_PRESS, BTN_TOOL_TRIPLETAP},
+ {CST816X_RESERVED, KEY_RESERVED},
+ {CST816X_RESERVED, KEY_RESERVED},
+ {CST816X_RESERVED, KEY_RESERVED},
+ {CST816X_RESERVED, KEY_RESERVED},
+ {CST816X_RESERVED, KEY_RESERVED},
+ {CST816X_RESERVED, KEY_RESERVED},
+ {CST816X_RESERVED, KEY_RESERVED},
+ {CST816X_RESERVED, KEY_RESERVED},
+ {CST816X_RESERVED, KEY_RESERVED},
+ {CST816X_RESERVED, KEY_RESERVED},
+};
+
+static int cst816x_i2c_read_register(struct cst816x_priv *priv, u8 reg,
+ void *buf, size_t len)
+{
+ int rc;
+ struct i2c_msg xfer[] = {
+ {
+ .addr = priv->client->addr,
+ .flags = 0,
+ .buf = &reg,
+ .len = sizeof(reg),
+ },
+ {
+ .addr = priv->client->addr,
+ .flags = I2C_M_RD,
+ .buf = buf,
+ .len = len,
+ },
+ };
+
+ rc = i2c_transfer(priv->client->adapter, xfer, ARRAY_SIZE(xfer));
+ if (rc != ARRAY_SIZE(xfer)) {
+ rc = rc < 0 ? rc : -EIO;
+ dev_err(&priv->client->dev, "i2c rx err: %d\n", rc);
+ return rc;
+ }
+
+ return 0;
+}
+
+static bool cst816x_process_touch(struct cst816x_priv *priv,
+ struct cst816x_touch_info *info)
+{
+ u8 raw[8];
+
+ if (cst816x_i2c_read_register(priv, CST816X_FRAME, raw, sizeof(raw)))
+ return false;
+
+ info->gesture = raw[0];
+ info->touch = raw[1];
+ info->abs_x = get_unaligned_be16(&raw[2]) & GENMASK(11, 0);
+ info->abs_y = get_unaligned_be16(&raw[4]) & GENMASK(11, 0);
+
+ dev_dbg(priv->dev, "x: %d, y: %d, t: %d, g: 0x%x\n", info->abs_x,
+ info->abs_y, info->touch, info->gesture);
+
+ return true;
+}
+
+static int cst816x_register_input(struct cst816x_priv *priv)
+{
+ priv->input = devm_input_allocate_device(priv->dev);
+ if (!priv->input)
+ return -ENOMEM;
+
+ priv->input->name = "Hynitron CST816X Touchscreen";
+ priv->input->phys = "input/ts";
+ priv->input->id.bustype = BUS_I2C;
+ input_set_drvdata(priv->input, priv);
+
+ for (unsigned int i = 0; i < ARRAY_SIZE(event_map); i++)
+ input_set_capability(priv->input, EV_KEY, event_map[i].code);
+
+ input_set_abs_params(priv->input, ABS_X, 0, 240, 0, 0);
+ input_set_abs_params(priv->input, ABS_Y, 0, 240, 0, 0);
+
+ return input_register_device(priv->input);
+}
+
+static void cst816x_reset(struct cst816x_priv *priv)
+{
+ if (priv->reset) {
+ gpiod_set_value_cansleep(priv->reset, 1);
+ msleep(50);
+ gpiod_set_value_cansleep(priv->reset, 0);
+ msleep(100);
+ }
+}
+
+static void report_gesture_event(const struct cst816x_priv *priv,
+ enum cst816x_gestures gesture, bool touch)
+{
+ u16 key = event_map[gesture & 0x0F].code;
+
+ if (key != KEY_RESERVED)
+ input_report_key(priv->input, key, touch);
+}
+
+/*
+ * Supports five gestures: TOUCH, LEFT, RIGHT, FORWARD, BACK, and LONG_PRESS.
+ * Reports surface interaction, sliding coordinates and finger detachment.
+ *
+ * 1. TOUCH Gesture Scenario:
+ *
+ * [x/y] [touch] [gesture] [Action] [Report ABS] [Report Key]
+ * x y true 0x00 Touch ABS_X_Y BTN_TOUCH
+ * x y true 0x00 Slide ABS_X_Y
+ * x y false 0x05 Gesture BTN_TOUCH
+ *
+ * 2. LEFT, RIGHT, FORWARD, BACK, and LONG_PRESS Gestures Scenario:
+ *
+ * [x/y] [touch] [gesture] [Action] [Report ABS] [Report Key]
+ * x y true 0x00 Touch ABS_X_Y BTN_TOUCH
+ * x y true 0x01 Gesture ABS_X_Y BTN_FORWARD
+ * x y true 0x01 Slide ABS_X_Y
+ * x y false 0x01 Detach BTN_FORWARD | BTN_TOUCH
+ */
+static irqreturn_t cst816x_irq_cb(int irq, void *cookie)
+{
+ struct cst816x_priv *priv = cookie;
+ struct cst816x_touch_info info;
+
+ if (!cst816x_process_touch(priv, &info))
+ goto out;
+
+ if (info.touch) {
+ input_report_abs(priv->input, ABS_X, info.abs_x);
+ input_report_abs(priv->input, ABS_Y, info.abs_y);
+ input_report_key(priv->input, BTN_TOUCH, 1);
+ }
+
+ if (info.gesture) {
+ report_gesture_event(priv, info.gesture, info.touch);
+
+ if (!info.touch)
+ input_report_key(priv->input, BTN_TOUCH, 0);
+ }
+
+ input_sync(priv->input);
+
+out:
+ return IRQ_HANDLED;
+}
+
+static int cst816x_probe(struct i2c_client *client)
+{
+ struct cst816x_priv *priv;
+ struct device *dev = &client->dev;
+ int error;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->dev = dev;
+ priv->client = client;
+
+ priv->reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+ if (IS_ERR(priv->reset))
+ return dev_err_probe(dev, PTR_ERR(priv->reset),
+ "reset gpio not found\n");
+
+ cst816x_reset(priv);
+
+ error = cst816x_register_input(priv);
+ if (error)
+ return dev_err_probe(dev, error, "input register failed\n");
+
+ error = devm_request_threaded_irq(dev, client->irq, NULL, cst816x_irq_cb,
+ IRQF_ONESHOT, dev->driver->name, priv);
+ if (error)
+ return dev_err_probe(dev, error, "irq request failed\n");
+
+ return 0;
+}
+
+static const struct i2c_device_id cst816x_id[] = {
+ { .name = "cst816s", 0 },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, cst816x_id);
+
+static const struct of_device_id cst816x_of_match[] = {
+ { .compatible = "hynitron,cst816s", },
+ { }
+};
+MODULE_DEVICE_TABLE(of, cst816x_of_match);
+
+static struct i2c_driver cst816x_driver = {
+ .driver = {
+ .name = "cst816x",
+ .of_match_table = cst816x_of_match,
+ },
+ .id_table = cst816x_id,
+ .probe = cst816x_probe,
+};
+
+module_i2c_driver(cst816x_driver);
+
+MODULE_AUTHOR("Oleh Kuzhylnyi <kuzhylol@xxxxxxxxx>");
+MODULE_DESCRIPTION("Hynitron CST816X Touchscreen Driver");
+MODULE_LICENSE("GPL");
--
2.34.1