[9fans] writing cds

[anothy@cosym.net]

i'm trying to burn a CD using cdfs. i've got the
image read just fine (it's quite big, basically a
full cd). i can write the image just fine onto a
CD-RW disk, and that disk works great (confirmed
in a friend's Win32 box). but when i try to write
it onto a blank 700MB CD-R disk, i get this:
	: anothy; cp lib/foo.cd /mnt/cd/wd
	cp: error writing /mnt/cd/wd/foo.cd: cmd #2a: invalid field in cdb
this happens about 15 seconds into the cp process.
i can't find it in the source for cdfs (although
mmc.c does have this:
	cmd[0] = 0x2a;	/* write */
which seems informative). i've written to these
oversized disks before without issue (although i
can't remember if i've ever written _data_, as
opposed to just audio). anyone know what's going
on, before i plop debug prints in and eat a few
more CDs?
-α.