Hardkernel finally released the AML_LIBS for the C2 that allow hardware decoding! So I made a PKGBUILD for it (well actually I just tweaked my C1 PKGBUILD to use the C2 libs and build flags.) Enjoy.
Step 1 (Prep and Download):
•Make sure you have 'base-devel' and 'git' packages.
•Create a directory to hold the repository directory.
•cd into that directory and type $this->bbcode_second_pass_code('', 'git clone https://aur.archlinux.org/kodi-c2-fb.git')
•cd to the new directory.
Step 2 (Build):
•To build the package will take a couple hours, so I recommend you do this in a 'screen' window. If you don't know what that is, google it, it's a Godsend for long tasks in ssh.
•Type $this->bbcode_second_pass_code('', 'makepkg -s') to start the package build process.
•The build text will not show onscreen, it will be sent to a log instead. If you want to check the status of the actual configure/build, cd into the src/xbmc-****** directory and cat the build.log file.
Step 3 (Install):
•When it is done making the package, just install the kodi-c2-fb and the kodi-c2-eventclients-fb with "pacman -U"
•Install any other packages for optional functionality. Eg. Pulseaudio, polkit, etc.
Note: It does work, however it seems pretty buggy. While testing it so far, I ran into numerous issues. EDIT: See bottom of post for updated info.
First, the refresh rate change to match the video doesn't work, it kicks me to an unsupported mode permanently until restart.
Second, moving between menu items is kinda jittery, this is new and wasn't existent in my test builds a few weeks ago.
Third, DTS seems passthrough cuts out every couple seconds, though could be because my DTS tracks are 1,536Kbps and that might be too much for it? Also there is only support for stereo, multichannel is only available via passthrough.
Finally, there is an issue with it kodi reporting skipped frames, I don't notice any choppiness so I don't think it really is, the C1 had the same problem.
EDIT: Update on the bugginess:
1. The choppy menu movement is on mdrjr's list of things to fix in the Mali fb driver. He suspects the vsync implementation. Hopefully will be fixed soon.
2. The method I use to block the console from appearing over the kodi GUI is insufficient, I hope update the PKGBUILD with a new, and much better, implementation in the coming days.
3. The random audio drops on DTS and transcoded AC3 passtgrough seems to be related to the audio driver and the sysfs file in /sys/class/audiodsp/digital_codec" I guess it must be updated with the correct codec ("3" for DTS and "2" for AC3), however doing so while kodi is running doesn't change anything. The only way to get it to work is to update the file's value prior to opening kodi, but that causes PCM to distort and doesn't work 100% of the time. It looks like HK knows of this issue and may be working on a fix (though I only saw it talked about for android...)
4. The black screen problem after having Kodi automatically match the refresh rate seems to be fixed by disabling HDMI hotplugging in the boot.ini file as "setenv hpd true". Note: If you add anything to the "setenv bootargs, it may become too long and the whole line may not be parsed, a fix is to split the line into two lines with different variable names (eg. setenv bootargs0 "..." and setenv bootargs1 "...") and combine them in a third line (setenv bootargs " ${bootargs0} ${bootargs1}").
5. Going over a few patches, I learned that the "skipped" frames statistic is incorrect. There are, infact, no skipped frames. There are patches to disable the skipped frame counter, though it I see that as unnecessary.