OSD:re - a new firmware for the Neuros OSD
  Gerry Boland <ger *surname* @gmail.com>

      (For information on how to build your own firmware, see INSTALL)

The Neuros OSD is an ARM-based embedded device specialising in video playback
and recording. The original firmware is (as of now: 2011) several years old and
has seen no improvements in the last 2 years.

The original firmware is a bunch of Makefiles and scripts thrown together, and
it can be very difficult to figure out what's happening. The UI is based on Qt
but feels rather unresponsive on the poor 200Mhz CPU.

The video playback & record is handled by propietary code running on a C54x DSP,
which we (i.e. applications running on the ARM core) have no access to aside 
from via propietary kernel modules (all closed code written by Ingenient).

Goals of this project are:
1. Use a modern and pre-existing build system to construct firmware images.
2. Use a more modern toolchain than the supplied gcc3.4, tailored to the 
   arm926ej-s chip. Specifically EABI should be enabled, to increase floating-
   point arithmetic performance.
3. A newer kernel would be nice. But this may cause problems with the propietary
   modules, so needs investigating. Ultimate goal would be to port drivers to
   latest kernel release and push them upstream.
4. Allow all the primary features of the OSD to be controllable via command-
   line. It should be a scripting heaven :)
5. Investigate a read-write filesystem.
6. GUI: This will require investigation. With newer toolchain, it possible
   Neuros' UI will improve speed-wise. But personally I'd love to use QtQuick[1]
   to design an UI which works more efficiently, and is easier to hack on.
7. Performance tweaks, make this thing fly!
8. SDK to help everyone join in.
9. Document everything.


Progress so far:
1. The Buildroot[2] project is a neat set of Makefiles and patches which make
   embedded development quite pleasant. It incorporates much software for free,
   as easy as ticking a box.

   It generates a basic Neuros OSD kernel and root image right now (not a 
   flash-able UPK yet).

2. Using Crosstool-ng[3] one can build a toolchain with gcc 4.4.3 and uClibc
   0.9.30.1 which works well on the OSD. It supports EABI. It needs thorough 
   testing!

3. Right now I've kept Neuros' 2.6.15 kernel, but have added
    - EABI support, using a patch set[4] (not all applied cleanly)
    - EABI caused unusual error, most network communication would fail. Running
      wireshark showed that packets the OSD was sending were bad - their header
      checksum was incorrect. Turned out that the assembly code in 
      include/asm-arm/checksum.h needed a fix found in later kernels.
    - Squashfs support
   Propietary modules initially refused to insmod with
      version magic '2.6.15 preempt ARMv5 gcc-3.4' should be '2.6.15 preempt ARMv5 gcc-4.4'
   but using a Hex editor to change the version string has made them work.
   This hack will need careful testing.

4. Todo! The Busybox-based ash is there, as is lua.

5. I want to add mini_fo to add a read-write overlay on the read-only
   filesystem. But where will it store data? Is it safe?

6. Buildroot builds the latest Qt libraries running on top of TinyX. Performance
   needs to be determined, but [6] shows there may be hope.
   
7. Performance
    - uboot very kindly sits there for 3 seconds waiting for you to interrupt.
      I genuinely think 1 second is enough, and I'll make it easy to extend this
    - Could compress uImage with LZMA, see if that speeds things up. It would
      good to determine if the flash or the CPU is the bottleneck.
    - squashfs is reported to have improved performance over cramfs. Try it.
    - kernel contains several pauses in boot - mostly at CF card & SD card 
      driver init. 
    - kernel rather verbose output can be quietened [7]

8. SDK: The Buildroot guys are working on automatic generation of an SDK with
   their system. I'm waiting for this to materialise.

9. I'll try to doc as I go.


Notes
-------------
uClibc is currently built with minimal debugging enabled

Read-only filesystem causes problems, especially in /etc


[1] http://qt.nokia.com/products/qt-quick
[2] http://buildroot.uclibc.org/
[3] http://ymorin.is-a-geek.org/dokuwiki/projects/crosstool
[4] http://www.codesourcery.com/sgpp/lite/arm/portal/kbentry22
[5] http://www.denx.de/wiki/bin/view/Know/MiniFOHome
[6] http://www.youtube.com/watch?v=AvFwzyCknLg
[7] http://thread.gmane.org/gmane.linux.kernel.embedded/2281