Input: psmouse - add support for SMBus companions

This provides glue between PS/2 devices that enumerate the RMI4 devices
and Elan touchpads to the RMI4 (or Elan) SMBus driver.

The SMBus devices keep their PS/2 connection alive. If the initialization
process goes too far (psmouse_activate called), the device disconnects
from the I2C bus and stays on the PS/2 bus, that is why we explicitly
disable PS/2 device reporting (by calling psmouse_deactivate) before
trying to register SMBus companion device.

The HID over I2C devices are enumerated through the ACPI DSDT, and
their PS/2 device also exports the InterTouch bit in the extended
capability 0x0C. However, the firmware keeps its I2C connection open
even after going further in the PS/2 initialization. We don't need
to take extra precautions with those device, especially because they
block their PS/2 communication when HID over I2C is used.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/psmouse.h

@@ -209,5 +209,34 @@ static struct psmouse_attribute psmouse_attr_##_name = {			\
 		   &(psmouse)->ps2dev.serio->dev,	\
 		   psmouse_fmt(format), ##__VA_ARGS__)
 
+#ifdef CONFIG_MOUSE_PS2_SMBUS
+
+int psmouse_smbus_module_init(void);
+void psmouse_smbus_module_exit(void);
+
+struct i2c_board_info;
+
+int psmouse_smbus_init(struct psmouse *psmouse,
+		       const struct i2c_board_info *board,
+		       const void *pdata, size_t pdata_size,
+		       bool leave_breadcrumbs);
+void psmouse_smbus_cleanup(struct psmouse *psmouse);
+
+#else /* !CONFIG_MOUSE_PS2_SMBUS */
+
+static inline int psmouse_smbus_module_init(void)
+{
+	return 0;
+}
+
+static inline void psmouse_smbus_module_exit(void)
+{
+}
+
+static inline void psmouse_smbus_cleanup(struct psmouse *psmouse)
+{
+}
+
+#endif /* CONFIG_MOUSE_PS2_SMBUS */
 
 #endif /* _PSMOUSE_H */