CDRW UDF Filesystems for Linux? 11
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 (Score:1)
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 (Score:1)
More UDF links (Score:1)
Any UDF development would apply to DVD-RAM as well (Score:1)
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 (Score:1)
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 (Score:1)
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 (Score:1)
Write support (Score:1)
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? (Score:1)