drivers: input: touchscreen: Add an interface to expose TP features to userspace

* Needs to implement and register ops from TP driver
 * Access them via /sys/touchpanel/*
 * Export capacitive keys status

Change-Id: I2baa61c6055ca6f6207ac0d6f627fe03048ccfb6

drivers/input/touchscreen/Kconfig

@@ -1368,4 +1368,13 @@ config TOUCHSCREEN_SYNAPTICS_TCM
           To compile this driver as a module, choose M here: the
           module will be called synaptics_tcm.
 
+config TOUCHSCREEN_COMMON
+	bool "Common touchscreen interface to interact with userspace"
+	default y
+	help
+	  Say Y here if you want to control touchpanel features via
+	  /sys/touchpanel.
+
+	  If unsure, say N.
+
 endif

drivers/input/touchscreen/Makefile

@@ -115,3 +115,4 @@ obj-$(CONFIG_TOUCHSCREEN_FTS)		+= focaltech_touch/
 obj-$(CONFIG_TOUCHSCREEN_SYNAPTICS_TCM)	+= synaptics_tcm/
 obj-$(CONFIG_TOUCHSCREEN_NT36XXX)	+= nt36xxx/
 obj-$(CONFIG_TOUCHSCREEN_XIAOMI_TOUCHFEATURE) += xiaomi/
+obj-$(CONFIG_TOUCHSCREEN_COMMON)	+= tp_common.o

drivers/input/touchscreen/tp_common.c

@@ -0,0 +1,29 @@
+#include <linux/input/tp_common.h>
+
+bool capacitive_keys_enabled;
+struct kobject *touchpanel_kobj;
+
+#define TS_ENABLE_FOPS(type)                                                   \
+	int tp_common_set_##type##_ops(struct tp_common_ops *ops)              \
+	{                                                                      \
+		static struct kobj_attribute kattr =                           \
+			__ATTR(type, (S_IWUSR | S_IRUGO), NULL, NULL);         \
+		kattr.show = ops->show;                                        \
+		kattr.store = ops->store;                                      \
+		return sysfs_create_file(touchpanel_kobj, &kattr.attr);        \
+	}
+
+TS_ENABLE_FOPS(capacitive_keys)
+TS_ENABLE_FOPS(double_tap)
+TS_ENABLE_FOPS(reversed_keys)
+
+static int __init tp_common_init(void)
+{
+	touchpanel_kobj = kobject_create_and_add("touchpanel", NULL);
+	if (!touchpanel_kobj)
+		return -ENOMEM;
+
+	return 0;
+}
+
+core_initcall(tp_common_init);

include/linux/input/tp_common.h

@@ -0,0 +1,15 @@
+#include <linux/kobject.h>
+
+extern bool capacitive_keys_enabled;
+extern struct kobject *touchpanel_kobj;
+
+struct tp_common_ops {
+	ssize_t (*show)(struct kobject *kobj, struct kobj_attribute *attr,
+			char *buf);
+	ssize_t (*store)(struct kobject *kobj, struct kobj_attribute *attr,
+			 const char *buf, size_t count);
+};
+
+int tp_common_set_capacitive_keys_ops(struct tp_common_ops *ops);
+int tp_common_set_double_tap_ops(struct tp_common_ops *ops);
+int tp_common_set_reversed_keys_ops(struct tp_common_ops *ops);