platform/chrome: Add ChromeOS EC ISHTP driver

This driver implements a slim layer to enable the ChromeOS
EC kernel stack (cros_ec) to communicate with ChromeOS EC
firmware running on the Intel Integrated Sensor Hub (ISH).

The driver registers a ChromeOS EC MFD device to connect
with cros_ec kernel stack (upper layer), and it registers a
client with the ISH Transport Protocol bus (lower layer) to
talk with the ISH firwmare. See description of the ISHTP
protocol at Documentation/hid/intel-ish-hid.txt

Signed-off-by: Rushikesh S Kadam <rushikesh.s.kadam@intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Reviewed-by: Jett Rink <jettrink@chromium.org>
Tested-by: Jett Rink <jettrink@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

drivers/platform/chrome/Kconfig

@@ -71,6 +71,19 @@ config CROS_EC_RPMSG
 	  To compile this driver as a module, choose M here: the
 	  module will be called cros_ec_rpmsg.
 
+config CROS_EC_ISHTP
+	tristate "ChromeOS Embedded Controller (ISHTP)"
+	depends on MFD_CROS_EC
+	depends on INTEL_ISH_HID
+	help
+	  If you say Y here, you get support for talking to the ChromeOS EC
+	  firmware running on Intel Integrated Sensor Hub (ISH), using the
+	  ISH Transport protocol (ISH-TP). This uses a simple byte-level
+	  protocol with a checksum.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called cros_ec_ishtp.
+
 config CROS_EC_SPI
 	tristate "ChromeOS Embedded Controller (SPI)"
 	depends on MFD_CROS_EC && SPI

drivers/platform/chrome/Makefile

@@ -7,6 +7,7 @@ obj-$(CONFIG_CHROMEOS_LAPTOP)		+= chromeos_laptop.o
 obj-$(CONFIG_CHROMEOS_PSTORE)		+= chromeos_pstore.o
 obj-$(CONFIG_CHROMEOS_TBMC)		+= chromeos_tbmc.o
 obj-$(CONFIG_CROS_EC_I2C)		+= cros_ec_i2c.o
+obj-$(CONFIG_CROS_EC_ISHTP)		+= cros_ec_ishtp.o
 obj-$(CONFIG_CROS_EC_RPMSG)		+= cros_ec_rpmsg.o
 obj-$(CONFIG_CROS_EC_SPI)		+= cros_ec_spi.o
 cros_ec_lpcs-objs			:= cros_ec_lpc.o cros_ec_lpc_reg.o