@cfh11 that sounds like a completely different problem.
@qwerty12: i have no such file, however there is /usr/sbin/osso-mass-storage-enable.sh, I'll try to understand how it works and play around with it.
@volt: you mean the second. the first one is the one containing the vfat. the 2nd one is the one that is unusable. I think I don't even have a sd card. That is, i didn't add one myself after getting the phone.

the big question is: why does the phone expose a 2nd blockdevice which is not even usable because there is no device (sd card) for it?

perhaps its related to the whole dumb/smart charging cable issue? cant say i know too much about it so forgive my ignorance if i'm completely in the wrong area!

As a workaround, use FM transmitter or bluetooth, while waiting for a working solution to this. I myself like to be cable-free, but I also understand your PoV. There is even a nifty application for xferring mp3 tags over RDS in the repositories.

Okay, we did some experimenting:
- the error message is "onleesbaar" (unreadable)
- by playing with /usr/sbin/osso-usb-mass-storage-enable.sh and especially with the g_file_storage module and it's options (rmmod and modprobe are our friend), we managed to present the following over usb:
1) 2 devicefiles, one for the sdcard (doing nothing) and one for the vfat partition (this is the default way) -> same error
2) 1 devicefile, one for the vfat partition -> same error
3) 1 devicefile, one for the complete flash storage with mbr (/dev/mmcblk0) -> same error
4) 2 devicefiles, one for the sdcard (doing nothing) and one for the complete flash storage with mbr (/dev/mmcblk0) -> same error

From the manual of the car we can read there are the following limitations:
max 500 directories
max 64000 files
min 256 MB of size
support for playback of mp3, wma, and wav files. other files will just be ignored.

We will do further experiments like copying the entire vfat contents to a usb stick, trying to clean up the special dotfiles, etc. *sigh*

Update: we copied all files from the /home/user/MyDocs/ directory to a USB stick with rsync.
One file wasn't copied by rsync (/home/user/MyDocs/._?) - also tried to just cp it - but besides from that, all files and directories are the exact same on the USB stick as on the phone.
The car recognized the USB stick and immediately started playing the songs that are on it.
*puzzled*

I think you are on to something here....

this seems to be about charging or not charging?
http://talk.maemo.org/archive/index.php/t-38230.html

The phone doesn't charge in the car indeed, but it doesn't bother me that much.
Our real issue is that the car doesn't read the music from the n900, i don't think charging has much to do with that

for that error you should check if the device is actually in use, and what is using it.

For me the issue was Easy debian, it would stay open and not allow use of the mass storage mode.
I just started using the "Close Debian" app after using debian, and this allows me to use mass storage mode once again

No, I don't think it has something to do with the charging issues either.

"2) 1 devicefile, one for the vfat partition -> same error" - this sounds like the best setup for the car to find the right partition. I would have thought that would work. And you tried copying over the files to another device, and no problems with the files/structure... So it looks more like it has to do with the file system/partitioning. Which I guess was what you believed all along.

So I did a little offsite googling. This might be of interest:

"volvo_fox
11-24-2009, 05:09 PM
The drive is formatted with fat32 from the producer. <br>I have tried to format it in windows vista. But it is still unreadable.<br>I cannot delete the partition in windows either, so I had to use a third party software (active partition manager) to delete the partition on the usb. <p>I created a smaller partition, approx 8 GB and copied some music to it. My car was able to read it. " (...) "Repartitioned the usb drive and made it use all its space. Formatted it with fat32.<p>Copied 10 cd's to the drive and tested. My Volvo reads and plays the song wonderfully.<p>Guess the partition from the producer was not compatible with Volvo.<p>"

http://forums.swedespeed.com/archive.../t-129594.html

Thanks Volt,
Maybe Nokia also used "unusual" tools to create the vfat filesystems.
If/when I find the time, I'll reformat the partition (or a microSD card) using mkfs.vfat and try it out.