Hello shrike-list,
recently I wrote about my problems with playing a DVD under RH9.
<20030529220557.3b9681d5.dvg@xxxxxxxxx>
When using ide-scsi /var/log/messages told me
kernel: ide-scsi: expected 8192 got 16384 limit 8192
kernel: ide-scsi: The scsi wants to send us more data than expected - discarding data
But when removing ide-scsi I get the following from ogle / libdvdread:
libdvdread: Can't seek to block 256
In case of this error the ogle-user mailing list proposes to use ide-scsi.
Duh.
So I spent a little time on looking at the seeking problem that libdvdread faces.
strace identifies the system call that fails as:
[..]
[pid 14412] _llseek(3, 524288, 0xbfffb810, SEEK_SET) = -1 EINVAL (Invalid argument)
[..]
The _llseek manpage says that EINVAL occurs when "whence" (here SEEK_SET) is invalid.
The system call was invoked by libdvdcss doing (src/device.c):
i_seek = lseek( dvdcss->i_read_fd,
(off_t)i_blocks * (off_t)DVDCSS_BLOCK_SIZE,
SEEK_SET );
with fd==3 and i_blocks==256. Nothing unusual on the side of libdvdcss here.
Quote from Håkan Hjort <20021009164436.GB10689@xxxxxxxxxxxxxxxxxxxxxx> in the
ogle-user list:
"Not allowing one to seek to block 256 of a DVD, that surely is several
Gigabytes large (i.e. >1M blocks), is something that likely is the
kernels fault. We've had several reports about this.. some kernels
work some don't others are successful with the same kernels versions
that fail for others... Using ide-scsi (and the correct device node)
solved it for some, and failed to cure it for others...
So nothing conclusive yet.
It seem that when one opens the DVD device node, the kernel has
decided that it has a size of 0. So you may open it but any
seek/read will fail."
And later in the same thread, after the person having the seek problem was
helped by using ide-scsi (grrr :-) :
"Great that it works. Now if we could just get some RedHat/Kernel developers
intrested in fixing the underlying bug.
(http://wwww.dtek.chalmers.se/~dvd/dist/dvd_test.tar.gz can be used as a test
aplication)."
<HINT, HINT>
Ehm. So, I still can't watch DVDs, but maybe someone can tell me where to
get a kernel that works? 2.4.20-8 and 2.4.20-13.9 are showing this
behaviour.
Digging deeper into this problem starts to be fun, but I have only very
limited knowledge about kernel internals :-)
Regards,
Daniel
