Dingux News - 31st July 2009

SHOWSTOPPER
I have minor good news: both the network over USB and FTP server work fine.

And here are the bad news: there is a data corruption problem when writing to the miniSD in linux. Some users had reported filesystem corruption but seemed to be a minority and I suspected could be a compatibilidy problem in a certain type/brand of card.

This is a fscking showstopper and has become right now #1 in the priority list. The only workaround as of now is to NOT WRITE AT ALL to the miniSD. I know this means states cannot be saved (brightness, volume, game states, etc) since there is right now no safe place to store them.

I will dedicate all efforts to identify the problem and fix it as soon as possible, but this is likely to take some time since the error is not deterministic nor predictable.

If you want to check it out yourself, run in your A320 the following commands:

cd /boot
dd if=/dev/urandom bs=1M count=100 | tee test1.bin | md5sum
md5sum test1.bin
cp test1.bin test2.bin
md5sum test2.bin

The three calculated MD5 sums should be equal (the first one is calculated from the pseudorandom data as it comes out of /dev/urandom, the second one is calculated from the same data stored in file test1.bin, and the third is caculated from file test2.bin which is a copy of test1.bin.

The corruption seems to happen on writing. Reading is ok, which you can test yourself by calculating the MD5 sum of a large file many times. All will yield the same value, whereas whenever you copy the data to a new file the MD5 sum will change.

NOTE that this is not filesystem related, i.e. happens in the FAT and ext2/ext3 releases.

Timidity patch set
Robert2098 cleverly pointed out that a patch set is necessary for MIDI music in some games (those that use SDL_mixer, actually). Since SDL_mixer is part of the rootfs, I think that the patch set must be included too.

However, when I was just about to use the set found at the SDL_mixer page, I noticed that there is also the freepat project, which is the patch set included in my Ubuntu 9.04 desktop.

So, a question for those knowledgeable in the matter: which patch set should I include? (the one available in the SDL_mixer page is about 18M while freepat is about 33M... smaller is better given the limited amount of memory in the A320).

On a side note, I added support for partitionless cards. Not sure if it's really a good idea to allow two different card layouts. Will go out in the next release (which will include dual-boot and system, since changes in both were required). Bastian linked to a patch for u-boot so I thought it would be relatively easy to fix, but turned out not to work, but at that time I was already into it and ended up with my own working fix. Had to modify also the initramfs embedded in the kernel because it must now try two different devices as boot partition: mmcblk0 (partitionless cards) and mmcblk0p1 (partitioned cards).