README.crystalhd

18-02-2012

Porting the crystalhd to the wetab:18-02-2012

First the kernel driver is needed.
Started with this git :  http://linuxtv.org/git/jarod/crystalhd.git

The kernel driver is not a big problem, just copy the directory kernel_mods/crystalhd to the kernel tree drivers/staging/crystalhd and enable the module
in the kernel config.

The module should load automaticly, but we need to chmod the device (/dev/crystalhd)  to 0644.

Next we need libcrystalhd, the userspace library.
This is slighty more interesting.
This library is using posix Shared Memory, and Android doesn't use that.
(If applications are not nice, they can kill youre system, especially since
android might kill any application and then SHM is not freed.
This application wil resuse its shared memory, so I do not believe this
is a problem).
All shm is handled by the kernel, not from userspace.
So we need a kernel with SHM enabled.

Next step is to interface between a user programm and the kernel, normally
the C library will do that. But not the bionic libc used by android.
In 2008 it was enabled but only for arm. For x86 it was never enabled.

There is however a syscall interface in this libc, so we "only" need
to create some functions (like shmget) call the correct syscall
(IPC-117) and create our own shm.h.
N.B. the one I created will only work on recent kernels on 32 bit x86.

I also create a small posix_memalign, because android doesn't have that one.

All in all this libcrystalhd will compile, and is working on my system
(tested with a ffmpeg and libffmpeg, It did about 60fps on a H264 decode,
decode only no display at this time)

TODO: libffmpeg with support for crystalhd : almost done, working in test.
TODO: a video displayer, mayby dolphin-playerx86: currently in test, but
problems with displaying (too slow), might have something todo with the i915.)