Sorry if here's stuff you know already. I just want to clarify what it is I'm after.
I gave this a bit more thought and realized not providing the nfo isn't quite what Ì was looking for. I would like to be able to write nfo files through vdrnfofs. Or to be more specific I would like xbmc to be able to write nfo file for vdrnfofs provided recordings.
The scrapers them self don̈́'t create the nfo-files. Scraper can fetch information for example about a movie, tv-show or tv-show episode from internet. There are scrapers at least for imdb.com, themoviedb.com and thetvdb.com.
XBMC scraper fetches the information and xbmc saves it in library database (default db is sqlite, MySql can be used). When browsing films or tvshows in library-mode information from the database is displayed.
From video settings it is possible to export the video library and at that time xbmc saves the nfo-file to the same folder as the video-file. Exporting library is needed for backup but also for modifying the nfo-file by hand an re-reading modified info back to xbmc.
I would like to use xbmc provided information instead of vdr-provided. At least here in Finland tv epg-data is very limited and close to useless. It is possible to use info from the net in xbmc (saved in database) instead of the local nfo file (provided by vdrnfofs) but exporting the nfo isn't possible because vdrnfofs is read-only.
At the moment I've been able to import vdr recordings in to xbmc library without vdrnfofs using a feature called File Stacking but this only works for movies and not for tv-shows and is a bit cumbersome.
It would be easier to manage the library with something like vdrnfofs providing an xbmc friendly folder structure for vdr recordings and let xbmc provide video info.
If the two-way mapping of nfo files would work I believe when exporting the library the "real" nfo should be written to disk in whole and title and plot information should be taken and written to vdr:s info file in T and D rows. Idea being that vdr would display information that xbmc scraped from internet. This might get to be a bit fiddly and I don't know if it's really needed.
XBMCs wiki has the different nfo file structures. I have also attached some samples.
It's been a while since I've tested xbmcs PVR capable version so I don't know how much of these requirements are already provided there.