LF-191-2 i2c: introduce xen i2c paravirtualization driver

Add i2c backend frontend support.
The transaction only support one msg each time.
The frontend sends a request to backend, backend use i2c_transfer
to do real transaction to hardware and return the results to frontend.

Now i2cdump/get/set works.
In domu cfg file, use
"vi2c = ['backend=0,be-adapter=5a800000.i2c,addr=0x51;0x44']" to
create a dummy controller in frontend and allowed slaves in backend.

Currently the slave address check not added, it will be supported in
furture patch.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Acked-by: Leonard Crestez <leonard.crestez@nxp.com>

drivers/i2c/busses/Kconfig

@@ -1404,4 +1404,24 @@ config I2C_VIRTIO
           This driver can also be built as a module. If so, the module
           will be called i2c-virtio.
 
+config XEN_I2C_FRONTEND
+	tristate "Xen virtual i2c device support"
+	depends on XEN
+	default y
+	select XEN_XENBUS_FRONTEND
+	help
+	  This driver implements the front-end of the Xen virtual
+	  i2c device driver.  It communicates with a back-end driver
+	  in another domain which drives the actual i2c device.
+
+config XEN_I2C_BACKEND
+	tristate "Xen i2c-device backend driver"
+	depends on XEN_BACKEND
+	help
+	  The i2c-device backend driver allows the kernel to export its
+	  block devices to other guests.
+
+	  The corresponding Linux frontend driver is enabled by the
+	  CONFIG_XEN_I2C_FRONTEND configuration option.
+
 endmenu

drivers/i2c/busses/Makefile

@@ -147,4 +147,7 @@ obj-$(CONFIG_SCx200_ACB)	+= scx200_acb.o
 obj-$(CONFIG_I2C_FSI)		+= i2c-fsi.o
 obj-$(CONFIG_I2C_VIRTIO)	+= i2c-virtio.o
 
+obj-$(CONFIG_XEN_I2C_FRONTEND)	+= xen-i2cfront.o
+obj-$(CONFIG_XEN_I2C_BACKEND)	+= xen-i2cback.o
+
 ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG