@@ -369,6 +369,8 @@ nuttx/
|- fs/
| |- binfs/
| | `- README.txt
+ | |- cromfs/
+ | | `- README.txt
| |- mmap/
| | `- README.txt
| |- nxffs/
diff --git a/README.txt b/README.txt
index bc81c5be1b..57b46522cc 100644
--- a/README.txt
+++ b/README.txt
@@ -1937,6 +1937,8 @@ nuttx/
|- fs/
| |- binfs/
| | `- README.txt
+ | |- cromfs/
+ | | `- README.txt
| |- mmap/
| | `- README.txt
| |- nxffs/
diff --git a/fs/cromfs/README.txt b/fs/cromfs/README.txt
new file mode 100644
index 0000000000..6e27145698
--- /dev/null
+++ b/fs/cromfs/README.txt
@@ -0,0 +1,120 @@
+README
+======
+
+This directory contains the the CROMFS file system. This is an in-memory
+(meaning no block driver), read-only (meaning that can lie in FLASH) file
+system. It uses LZF decompression on data only (meta data is not
+compressed).
+
+It accesses the in-memory file system via directory memory reads and, hence,
+can only reside in random access NOR-like FLASH. It is intended for use
+with on-chip FLASH available on most MCUs (the design could probably be
+extended to access non-random-access FLASH as well, but those extensions
+are not yet in place).
+
+I do not have a good way to measure how much compression we get use LZF. I
+have seen 37% compression reported in other applications, so I have to
+accept that for now. That means, for example, that you could have a file
+system with 512Kb of data in only 322Kb of FLASH, giving you 190Kb to do
+ other things with.
+
+LZF compression is not known for its high compression rations, but rather
+for fast decompression. According to the author of the LZF decompression
+routine, it is nearly as fast as a memcpy!
+
+There is also a new tool at /tools/gencromfs.c that will generate binary
+images for the NuttX CROMFS file system and and an example CROMFS file
+system image at apps/examples/cromfs. That example includes a test file
+system that looks like:
+
+ $ ls -Rl ../apps/examples/cromfs/cromfs
+ ../apps/examples/cromfs/cromfs:
+ total 2
+ -rwxr--r--+ 1 spuda spuda 171 Mar 20 08:02 BaaBaaBlackSheep.txt
+ drwxrwxr-x+ 1 spuda spuda 0 Mar 20 08:11 emptydir
+ -rwxr--r--+ 1 spuda spuda 118 Mar 20 08:05 JackSprat.txt
+ drwxrwxr-x+ 1 spuda spuda 0 Mar 20 08:06 testdir1
+ drwxrwxr-x+ 1 spuda spuda 0 Mar 20 08:10 testdir2
+ drwxrwxr-x+ 1 spuda spuda 0 Mar 20 08:05 testdir3
+ ../apps/examples/cromfs/cromfs/emptydir:
+ total 0
+ ../apps/examples/cromfs/cromfs/testdir1:
+ total 2
+ -rwxr--r--+ 1 spuda spuda 249 Mar 20 08:03 DingDongDell.txt
+ -rwxr--r--+ 1 spuda spuda 247 Mar 20 08:06 SeeSawMargorieDaw.txt
+ ../apps/examples/cromfs/cromfs/testdir2:
+ total 5
+ -rwxr--r--+ 1 spuda spuda 118 Mar 20 08:04 HickoryDickoryDock.txt
+ -rwxr--r--+ 1 spuda spuda 2082 Mar 20 08:10 TheThreeLittlePigs.txt
+ ../apps/examples/cromfs/cromfs/testdir3:
+ total 1
+ -rwxr--r--+ 1 spuda spuda 138 Mar 20 08:05 JackBeNimble.txt
+
+When built into NuttX and deployed on a target, it looks like:
+
+ NuttShell (NSH) NuttX-7.24
+ nsh> mount -t cromfs /mnt/cromfs
+ nsh> ls -Rl /mnt/cromfs
+ /mnt/cromfs:
+ dr-xr-xr-x 0 .
+ -rwxr--r-- 171 BaaBaaBlackSheep.txt
+ dr-xr-xr-x 0 emptydir/
+ -rwxr--r-- 118 JackSprat.txt
+ dr-xr-xr-x 0 testdir1/
+ dr-xr-xr-x 0 testdir2/
+ dr-xr-xr-x 0 testdir3/
+ /mnt/cromfs/emptydir:
+ drwxrwxr-x 0 .
+ dr-xr-xr-x 0 ..
+ /mnt/cromfs/testdir1:
+ drwxrwxr-x 0 .
+ dr-xr-xr-x 0 ..
+ -rwxr--r-- 249 DingDongDell.txt
+ -rwxr--r-- 247 SeeSawMargorieDaw.txt
+ /mnt/cromfs/testdir2:
+ drwxrwxr-x 0 .
+ dr-xr-xr-x 0 ..
+ -rwxr--r-- 118 HickoryDickoryDock.txt
+ -rwxr--r-- 2082 TheThreeLittlePigs.txt
+ /mnt/cromfs/testdir3:
+ drwxrwxr-x 0 .
+ dr-xr-xr-x 0 ..
+ -rwxr--r-- 138 JackBeNimble.txt
+ nsh>
+
+Everything I have tried works: examining directories, catting files, etc.
+The "." and ".." hard links also work:
+
+ nsh> cd /mnt/cromfs
+ nsh> cat emptydir/../testdir1/DingDongDell.txt
+ Ding, dong, bell,
+ Pussy's in the well.
+ Who put her in?
+ Little Johnny Green.
+
+ Who pulled her out?
+ Little Tommy Stout.
+ What a naughty boy was that,
+ To try to drown poor pussy cat,
+ Who never did him any harm,
+ And killed the mice in his father's barn.
+
+ nsh>
+
+To build the CROMFS file system, you would add the following to your
+configuration:
+
+1. Enable LZF
+
+ CONFIG_LIBC_LZF=y
+ CONFIG_LIBC_LZF_ALIGN=y
+ CONFIG_LIBC_LZF_HLOG=13
+ CONFIG_LIBC_LZF_SMALL=y
+
+2. Enable the CROMFS file system:
+
+ CONFIG_FS_CROMFS=y
+
+3. Enable the apps/examples/cromfs example:
+
+ CONFIG_EXAMPLES_CROMFS=y