On Friday, May 07 2004, Alan Stern wrote:
> On Thu, 6 May 2004, Andreas Hocevar wrote:
>
> > Since Kernel 2.6.4 the device hangs when burning CDs with cdrecord
or cdrdao
> > during sending the cue-sheet. The only case where this does not
happen is
> > when using tao mode for data CDs.
> >
> > Might this be a side-effect of the new routines checking for the "00
00 00
> > ..." packets that the genesys chip produces? When using verbose mode
in
> > cdrdao the cue-sheet is printed to the console, and it contains a
lot of "00
> > 00 00 ...".
>
> What new routines are you talking about?
I'm referring to the following section of Changelog-2.6.4 (without
having looked those routines up in the source code -- shame on me):
--- begin Changelog-2.6.4 ---
[PATCH] USB Storage: Handle excess 0-length data packets
This patch is an attempt to cope with Genesys Logic's, shall we say,
creative approach to implementing the USB protocols. Their high-speed
mass storage devices sometimes add an excess 0-length packet to the end
of
a data phase transmission. Of course we don't read that packet as part
of
the data phase; we see it as a 0-length CSW message. The real CSW
follows
immediately after. (Or sometimes a STALL follows immediately after,
with
the real CSW coming after that!)
The patch checks the results of the first attempt to read the CSW. If
it
sees a normal packet (not a STALL) with length 0, it retries the read.
Reports from two users indicate that it improves the performance of
their
USB-2 DVD drives.
--- end Ehangelog-2.6.4 ---
I will switch back to 2.6.3 and check again, but AFAIR it worked with
2.6.3.
> So far as I can tell, no amount of additional debugging information
will
> help fix the Genesys problem. What we need is expert advice from a
> technical person who understands how the chip works.
I tried to get in touch with them several months ago, but got no answer
(of course?). I think the best thing we can do is advice linux users not
to use enclosures with genesys chipset, until they give us enough
information to understand all facettes of their "creative approach" to
ehci implementation.
Andreas.
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