Input: add eGalaxTouch serial touchscreen driver

There are two EETI touchscreen drivers in the kernel (eeti_ts and
egalax_ts) but both are for I2C-connected panels. This is for a different,
serial and not multi-touch touchscreen panel. The protocol documentation is
at http://www.eeti.com.tw/pdf/Software%20Programming%20Guide_v2.0.pdf

Signed-off-by: Böszörményi Zoltán <zboszor@pr.hu>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/Kconfig

@@ -295,6 +295,16 @@ config TOUCHSCREEN_EGALAX
 	  To compile this driver as a module, choose M here: the
 	  module will be called egalax_ts.
 
+config TOUCHSCREEN_EGALAX_SERIAL
+	tristate "EETI eGalax serial touchscreen"
+	select SERIO
+	help
+	  Say Y here to enable support for serial connected EETI
+	  eGalax touch panels.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called egalax_ts_serial.
+
 config TOUCHSCREEN_FT6236
 	tristate "FT6236 I2C touchscreen"
 	depends on I2C

drivers/input/touchscreen/Makefile

@@ -35,6 +35,7 @@ obj-$(CONFIG_TOUCHSCREEN_EETI)		+= eeti_ts.o
 obj-$(CONFIG_TOUCHSCREEN_ELAN)		+= elants_i2c.o
 obj-$(CONFIG_TOUCHSCREEN_ELO)		+= elo.o
 obj-$(CONFIG_TOUCHSCREEN_EGALAX)	+= egalax_ts.o
+obj-$(CONFIG_TOUCHSCREEN_EGALAX_SERIAL)	+= egalax_ts_serial.o
 obj-$(CONFIG_TOUCHSCREEN_FT6236)	+= ft6236.o
 obj-$(CONFIG_TOUCHSCREEN_FUJITSU)	+= fujitsu_ts.o
 obj-$(CONFIG_TOUCHSCREEN_GOODIX)	+= goodix.o

drivers/input/touchscreen/egalax_ts_serial.c

@@ -0,0 +1,194 @@
+/*
+ * EETI Egalax serial touchscreen driver
+ *
+ * Copyright (c) 2015 Zoltán Böszörményi <zboszor@pr.hu>
+ *
+ * based on the
+ *
+ * Hampshire serial touchscreen driver (Copyright (c) 2010 Adam Bennett)
+ */
+
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"EETI Egalax serial touchscreen driver"
+
+/*
+ * Definitions & global arrays.
+ */
+
+#define EGALAX_FORMAT_MAX_LENGTH	6
+#define EGALAX_FORMAT_START_BIT		BIT(7)
+#define EGALAX_FORMAT_PRESSURE_BIT	BIT(6)
+#define EGALAX_FORMAT_TOUCH_BIT		BIT(0)
+#define EGALAX_FORMAT_RESOLUTION_MASK	0x06
+
+#define EGALAX_MIN_XC			0
+#define EGALAX_MAX_XC			0x4000
+#define EGALAX_MIN_YC			0
+#define EGALAX_MAX_YC			0x4000
+
+/*
+ * Per-touchscreen data.
+ */
+struct egalax {
+	struct input_dev *input;
+	struct serio *serio;
+	int idx;
+	u8 data[EGALAX_FORMAT_MAX_LENGTH];
+	char phys[32];
+};
+
+static void egalax_process_data(struct egalax *egalax)
+{
+	struct input_dev *dev = egalax->input;
+	u8 *data = egalax->data;
+	u16 x, y;
+	u8 shift;
+	u8 mask;
+
+	shift = 3 - ((data[0] & EGALAX_FORMAT_RESOLUTION_MASK) >> 1);
+	mask = 0xff >> (shift + 1);
+
+	x = (((u16)(data[1] & mask) << 7) | (data[2] & 0x7f)) << shift;
+	y = (((u16)(data[3] & mask) << 7) | (data[4] & 0x7f)) << shift;
+
+	input_report_key(dev, BTN_TOUCH, data[0] & EGALAX_FORMAT_TOUCH_BIT);
+	input_report_abs(dev, ABS_X, x);
+	input_report_abs(dev, ABS_Y, y);
+	input_sync(dev);
+}
+
+static irqreturn_t egalax_interrupt(struct serio *serio,
+				    unsigned char data, unsigned int flags)
+{
+	struct egalax *egalax = serio_get_drvdata(serio);
+	int pkt_len;
+
+	egalax->data[egalax->idx++] = data;
+
+	if (likely(egalax->data[0] & EGALAX_FORMAT_START_BIT)) {
+		pkt_len = egalax->data[0] & EGALAX_FORMAT_PRESSURE_BIT ? 6 : 5;
+		if (pkt_len == egalax->idx) {
+			egalax_process_data(egalax);
+			egalax->idx = 0;
+		}
+	} else {
+		dev_dbg(&serio->dev, "unknown/unsynchronized data: %x\n",
+			egalax->data[0]);
+		egalax->idx = 0;
+	}
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * egalax_connect() is the routine that is called when someone adds a
+ * new serio device that supports egalax protocol and registers it as
+ * an input device. This is usually accomplished using inputattach.
+ */
+static int egalax_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct egalax *egalax;
+	struct input_dev *input_dev;
+	int error;
+
+	egalax = kzalloc(sizeof(struct egalax), GFP_KERNEL);
+	input_dev = input_allocate_device();
+	if (!egalax) {
+		error = -ENOMEM;
+		goto err_free_mem;
+	}
+
+	egalax->serio = serio;
+	egalax->input = input_dev;
+	snprintf(egalax->phys, sizeof(egalax->phys),
+		 "%s/input0", serio->phys);
+
+	input_dev->name = "EETI eGalaxTouch Serial TouchScreen";
+	input_dev->phys = egalax->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_EGALAX;
+	input_dev->id.product = 0;
+	input_dev->id.version = 0x0001;
+	input_dev->dev.parent = &serio->dev;
+
+	input_set_capability(input_dev, EV_KEY, BTN_TOUCH);
+	input_set_abs_params(input_dev, ABS_X,
+			     EGALAX_MIN_XC, EGALAX_MAX_XC, 0, 0);
+	input_set_abs_params(input_dev, ABS_Y,
+			     EGALAX_MIN_YC, EGALAX_MAX_YC, 0, 0);
+
+	serio_set_drvdata(serio, egalax);
+
+	error = serio_open(serio, drv);
+	if (error)
+		goto err_reset_drvdata;
+
+	error = input_register_device(input_dev);
+	if (error)
+		goto err_close_serio;
+
+	return 0;
+
+err_close_serio:
+	serio_close(serio);
+err_reset_drvdata:
+	serio_set_drvdata(serio, NULL);
+err_free_mem:
+	input_free_device(input_dev);
+	kfree(egalax);
+	return error;
+}
+
+static void egalax_disconnect(struct serio *serio)
+{
+	struct egalax *egalax = serio_get_drvdata(serio);
+
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_unregister_device(egalax->input);
+	kfree(egalax);
+}
+
+/*
+ * The serio driver structure.
+ */
+
+static const struct serio_device_id egalax_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_EGALAX,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, egalax_serio_ids);
+
+static struct serio_driver egalax_drv = {
+	.driver		= {
+		.name	= "egalax",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= egalax_serio_ids,
+	.interrupt	= egalax_interrupt,
+	.connect	= egalax_connect,
+	.disconnect	= egalax_disconnect,
+};
+module_serio_driver(egalax_drv);
+
+MODULE_AUTHOR("Zoltán Böszörményi <zboszor@pr.hu>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL v2");

include/uapi/linux/serio.h

@@ -77,5 +77,6 @@
 #define SERIO_PS2MULT	0x3c
 #define SERIO_TSC40	0x3d
 #define SERIO_WACOM_IV	0x3e
+#define SERIO_EGALAX	0x3f
 
 #endif /* _UAPI_SERIO_H */