bus: mhi: Add userspace client interface driver

This MHI client driver allows userspace clients to transfer
raw data between MHI device and host using standard file operations.
Driver instantiates uci device object which is associated to device
file node. uci device object instantiates uci channel object when device
file node is opened. uci channel object is used to manage MHI channels
by calling MHI core APIs for read and write operations. MHI channels
are started as part of device open(). MHI channels remain in start
state until last release() is called on uci device file node. Device
file node is created with format

/dev/mhi_<controller_name>_<mhi_device_name>

Currently it supports LOOPBACK channel.

Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>

drivers/bus/mhi/Kconfig

@@ -20,3 +20,16 @@ config MHI_BUS_DEBUG
 	  Enable debugfs support for use with the MHI transport. Allows
 	  reading and/or modifying some values within the MHI controller
 	  for debug and test purposes.
+
+config MHI_UCI
+	tristate "MHI UCI"
+	depends on MHI_BUS
+	help
+	  MHI based userspace client interface driver is used for transferring
+	  raw data between host and device using standard file operations from
+	  userspace. Open, read, write, and close operations are supported
+	  by this driver. Please check mhi_uci_match_table for all supported
+	  channels that are exposed to userspace.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called mhi_uci.

drivers/bus/mhi/Makefile

@@ -1,2 +1,6 @@
 # core layer
 obj-y += core/
+
+# MHI client
+mhi_uci-y := uci.o
+obj-$(CONFIG_MHI_UCI) += mhi_uci.o