CDRW UDF Filesystems for Linux?

Hmmm...this must be the day of decent AC questions. Surprise surprise! Another Anonymous Cowards asks: "We're interesting in finding an existing implementation of the UDF file system for CDRW devices for Linux or other PC Unix operating systems. Does anyone know of such a beast? Otherwise, does anyone know where the UDF spec may be obtained?"

I wrote a complete UDF for Linux under contract

[gavinhall]

Posted by Scotty1024:

Happy news is at hand for those wishing a UDF filesystem for Linux. Under contract in '97 I wrote a complete R/W UDF kernel filesystem for Linux 2.0.34 that drove CD-R drives. YOu could pop a blank CD-R into the drive, mount it (autoformat on mount) and then proceed to copy files onto the disc or just cruise around it in your favorite shell checking out the contents. Pop the disc out, put it on the shelf, pop it back in later and add more goodies. Small files pigged the disc due to the packet size of the CD-R drive, but the overhead wasn't too terrible with larger files.
My understanding was that this code should have appeared in the Linux community within six months of it's being incorporated into their Linux based product.
If anyone knows the legalities of how to liberate this code legally please let me know. I am the original and sole author of the original code (it was based partly on the ext2fs) and the copyright to it was never transfered in a written contract to anyone.

I wrote a complete UDF for Linux under contract

[Eric Sharkey]

If you wrote code which was derived from GPL'd ext2fs code, then you only have two options. You can not distribute the code to anyone, or you can distribute it under the terms of the GPL. And "anyone" includes to the employer who paid you. If someone contracts you to write GPL software, you can resell/give it to anyone else you like as well. It's perfectly legal.

More UDF links

[Spruce Moose]

Ben Fennema's URl is actually here [calpoly.edu]

Any UDF development would apply to DVD-RAM as well

[BitMan]

Possibly DVD-RW and other, non-standard optical formats as well?

They want you to shove out over $100 for the NT drivers with most DVD-RAM kits (which are $500-1,000 themselves and only include Win9x drivers). If Linux had UDF support built-in, that would kick butt.

Since Linux has some PD (Panasonic's Phase-Dual technology, rewritable CDs in cases, used before CD-RW was standardized) support, does that use UDF too? Actually, know that I am thinking straight, I believe you had to format PD disks in another filesystem format under Linux (FAT16 or Ext2).

DVD-RAM works very similiar to PD (and, not surprisingly, came out of Panasonic).

I wrote a complete UDF for Linux under contract

[Bryan Andersen]

As I understand current copyright/contract law in USA. If you didn't transfer copyright as part of the contract, then you own the copyright for the code you wrote and can do as you please with it.

Others have commented on the GPL relationship.

CDRW Info

[Ben Fennema]

The major issues with CDRWs (above and beyond UDF write support) are:
1. CDRW drives don't do bad block remapping. So all bad block remapping has to be handled by the filesystem (UDF supports this). Of course, the drive also doesn't tell you when the write failed. So you have to read back the block to see if the write succeeded.... BUT

2. You can't just write blocks to a CDRW (well, ok.. you can.. BUT.. writing to CDRWs consists of writing packets.. now, your packet length could be 1 (in which case, your writing blocks to the media) but for each packet, you incure a 7 block overhead (4 blocks lead-in, 3 blocks lead-out or something along those lines). So, take 650 MB, divide by 8, and you get the size of the disk written with 1 block packets. Not very useful :)

3. Soo.. The packet size used is 32. Which means, when you write to the media, you have to write 32 blocks, or 64k.. Of course, as far as I know, the kernel has no support for doing this (the scsi generic module doesn't even allocate a large enough buffer to support it in userspace).

4. But remember, you gotta check if all the blocks in the packet were successfully written.. So after writing the 64k chunk, you have to read it back.. Fun!

5. And last but not least, unless you have a really new CD drive (and even then) you might not be able to read a fixed packet written disk in anything but your CDRW. If your looking for a new CD drive, you want a drive that handles both fixed and variable packet writen media.

I think I got all the gotchas for CDRWs. At least, as far as my knowledge goes. If I said something totally wrong, let me know :)

Answer

[CodeMunkey]

The problem is occurring because both your sound card and video card are using the same PCI bus. Your MP3 player is trying to put through as much data as possible, and when you scroll in netscape, the video card attempts to use the bus and the two conflict with each other causing audio/video stutters. I've heard of some sort of new PCI bus that allows parallel transmission...maybe it's a driver/bus master or something...not sure.

Write support

[dboynton]

The read support in UDF is coming along nicely, thanks to Ben Fennema [calpoly.edu]. Ben is working on the write support, but progress is hampered by lack of support in the IDE and SCSI CDROM drivers. They have no write (or DVD) support at all. That leaves us with the very ugly choice of going direct to the hardware from within a filesystem driver.

If anyone wants to help out with this project, what I think we need the most right now is someone to work on patches for the IDE & SCSI drivers to support the SCSI3/MMC command set. Please visit my TryLinux [trylinux.com] site and join the mailing list if you're interested.

Based on ext2fs code?

[SEWilco]

"it was based partly on the ext2fs" OK, in /usr/src/linux/fs/ext2/*.c I see an assortment of copyrights, starting with Linus'. I think all that falls under the GPL which is in /usr/src/linux/COPYING. So if you used some ext2fs code, your stuff is already liberated because it is already GPL. It should be labeled as such to avoid confusion. Check the company's web/FTP site and see if they already put the code there. If they're shipping their product, any customer should be able to inexpensively get the code from them and make it available per the GPL.