Input: synaptics-rmi4 - add SMBus support

Code obtained from https://raw.githubusercontent.com/mightybigcar/synaptics-rmi4/jf/drivers/input/rmi4/rmi_smbus.c
and updated to match upstream. And fixed to make it work.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Andrew Duggan <aduggan@synaptics.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/rmi4/Kconfig

@@ -27,6 +27,18 @@ config RMI4_SPI
 
 	  If unsure, say N.
 
+config RMI4_SMB
+	tristate "RMI4 SMB Support"
+	depends on RMI4_CORE && I2C
+	help
+	  Say Y here if you want to support RMI4 devices connected to an SMB
+	  bus.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called rmi_smbus.
+
 config RMI4_2D_SENSOR
 	bool
 	depends on RMI4_CORE

drivers/input/rmi4/Makefile

@@ -12,3 +12,4 @@ rmi_core-$(CONFIG_RMI4_F54) += rmi_f54.o
 # Transports
 obj-$(CONFIG_RMI4_I2C) += rmi_i2c.o
 obj-$(CONFIG_RMI4_SPI) += rmi_spi.o
+obj-$(CONFIG_RMI4_SMB) += rmi_smbus.o

drivers/input/rmi4/rmi_bus.h

@@ -104,6 +104,18 @@ rmi_get_platform_data(struct rmi_device *d)
 
 bool rmi_is_physical_device(struct device *dev);
 
+/**
+ * rmi_reset - reset a RMI4 device
+ * @d: Pointer to an RMI device
+ *
+ * Calls for a reset of each function implemented by a specific device.
+ * Returns 0 on success or a negative error code.
+ */
+static inline int rmi_reset(struct rmi_device *d)
+{
+	return d->driver->reset_handler(d);
+}
+
 /**
  * rmi_read - read a single byte
  * @d: Pointer to an RMI device