powerpc/powernv: Add driver for operator panel on FSP machines

Implement new character device driver to allow access from user space
to the operator panel display present on IBM Power Systems machines
with FSPs.

This will allow status information to be presented on the display which
is visible to a user.

The driver implements a character buffer which a user can read/write
by accessing the device (/dev/op_panel). This buffer is then displayed on
the operator panel display. Any attempt to write past the last character
position will have no effect and attempts to write more characters than
the size of the display will be truncated. The device may only be accessed
by a single process at a time.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/char/Kconfig

@@ -178,6 +178,20 @@ config IBM_BSR
 	  of threads across a large system which avoids bouncing a cacheline
 	  between several cores on a system
 
+config POWERNV_OP_PANEL
+	tristate "IBM POWERNV Operator Panel Display support"
+	depends on PPC_POWERNV
+	default m
+	help
+	  If you say Y here, a special character device node, /dev/op_panel,
+	  will be created which exposes the operator panel display on IBM
+	  Power Systems machines with FSPs.
+
+	  If you don't require access to the operator panel display from user
+	  space, say N.
+
+	  If unsure, say M here to build it as a module called powernv-op-panel.
+
 source "drivers/char/ipmi/Kconfig"
 
 config DS1620