How to Build
------------------------------------------------------------------------
Requires zlib development package (headers)

Just type 'make' to build.


Usage Notes
------------------------------------------------------------------------

usage: mkfs.axfs [OPTION]... dirname outfile
 -h            print this help
 -i infile     input file of the XIP information
 -n outfile    output inode number/name list
 -s            run silently
 -a            xip all files (no input file needed)
 -e            for any file in '-i infile', xip the entire file automatically
 dirname       root of the directory tree to be compressed
 outfile       output file



About the 'infile' File
------------------------------------------------------------------------
The input file is used to specify what pages in what files you want to
be marked for XIP. For anything not in this file, those page will be
compressed.
The input file is a CSV list containing three values in the following format:

path,offset,count

'path' is relative to the root of the filesystem image, perpended
with a . for purposes of later image generation.

'offset' is the number of bytes into the file where the 4KByte page to be
included in the XIP region is located.

'count' indicates the number of times the page was accessed. This is from the
output of the profiling tool in the driver. This value is not really used in
the creation of the AXFS image.


Example input file: (xip_sections.csv)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bin/busybox,0,103
bin/busybox,4096,103
bin/busybox,8192,103
bin/busybox,12288,103
bin/busybox,16384,103
lib/ld-2.23.so,0,113
lib/ld-2.23.so,4096,113
lib/ld-2.23.so,8192,113
lib/libc-2.23.so,0,113
lib/libc-2.23.so,4096,113
lib/libc-2.23.so,8192,113
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Generating the CSV file
------------------------------------------------------------------------
When profiling is enabled in the driver, each time a page fault occurs, the driver
records what file it was and what address/page it was. You can then read out that
record directly into a .csv file which can be passed to mkfs.axfs.
Below is the procedure.

1. Enable CONFIG_AXFS_PROFILING=y in the kernel

2. Create an AXFS image with NO XIP pages. The reason is you want to see how many times
   each page are the result of page fault.

3. Boot the kernel and run your application in its normal operating condition.

4. Read out the report to a file:

   $ cat /proc/axfs/volume0 > /tmp/xip_sections.csv

5. Transfer the xip_sections.csv file from the board to your development PC

6. Run mkfs.axfs again on the same root file system with NO CHANGES to the
   binaries that you used for profiling since the page fault report was specifically
   for those binaries. However, this time pass your .csv file as teh 'input' file

7 Disable CONFIG_AXFS_PROFILING in the kenel config (since it adds additional RAM and
  processing)

8. Reprogram kernel and rootfs.axfs and boot.



Automatically selecting all XIP option
------------------------------------------------------------------------
When the '-a' option is used, then the input file is not specified and
all executable ELF files (applications and libraries) will be automatically
selected for XIP.


Selecting XIP file by file
------------------------------------------------------------------------
When the '-e' option is used, then the input file is still read, but instead of listing
each page to be XIP-ed in the file, you just need to specify the file itself.
The advantage is that you do not have to use the profiling tool in the driver.
The disadvantage is that the entire file will be XIP (uncompressed) and the AXFS image
will be larger and take up more flash.

The 'offset' and 'count' parameters are ignored.

Example input file: (xip_files.csv)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bin/busybox,0,1
lib/debug/libstdc++.so.6.0.22,0,1
lib/ld-2.23.so,0,1
lib/libc-2.23.so,0,1
lib/libm-2.23.so,0,1
lib/libgcc_s.so.1,0,1
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



TODO
--------------------
0. Remove test code.

1. Writer will generate a temp image in RAM before writing the output file.
Not sure if this is a problem.  (this is also what cramfs does)

2. Check macro of AXFS_SIZE_WIDTH, and AXFS_OFFSET_WIDTH in axfs_fs.h. These
macros will determine the maximum FS size.  AXFS_OFFSET_WIDTH should be removed.
And verify MAXFSLEN macro in mkfs.axfs.c, since it seems inaccurate.

3. Align file name and data to u32 if needed.

4. Improve the search method of XIP files.

5. The name field of the root inode stores the root directory's path.  But
the path could be a relative path got from command line.  Figure out if this
is proper.

6. Use more efficient dynamic memory allocation for xipfileset[] and
xipchunkset[].

7. Potentially consolidate some CSV parsing functions, or even make them
inline.