Kconfig updates

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4608 42af7a65-404d-4744-a932-0658087f49c3

fs/mmap/Kconfig

@@ -3,4 +3,25 @@
 # see misc/tools/kconfig-language.txt.
 #
 
-comment "File mapping emulation"
+config FS_RAMMAP
+	bool "File mapping emulation"
+	default n
+	---help---
+		NuttX operates in a flat open address space and is focused on MCUs that do
+		support Memory Management Units (MMUs).  Therefore, NuttX generally does not
+		require mmap() functionality and the MCUs generally cannot support true
+		memory-mapped files.
+
+		However, memory mapping of files is the mechanism used by NXFLAT, the NuttX
+		tiny binary format, to get files into memory in order to execute them.
+		mmap() support is therefore required to support NXFLAT.
+
+		If FS_RAMMAP is defined in the configuration, then mmap() will
+		support simulation of memory mapped files by copying files whole
+		into RAM.  These copied files have some of the properties of
+		standard memory mapped files.
+
+		See nuttx/fs/mmap/README.txt for additonal information.
+
+if FS_RAMMAP
+endif