On 11/03/2011 10:15 AM, Thomas Schmitt wrote:
Which gives me something to work on. libburn does not take into
respect the Block Descriptor of 8 bytes which sits between
Mode Data Header and mode page.
So it misinterpets the result and demands the wrong Allocation
Length.
This error is explainable by my reading of MMC-5 which prescribes
in table 653:
"Block Descriptor Length = 0"
MMC-1 on the other hand has in Annex B.4.1 :
"The Mode Parameter Block Descriptor does not apply to ATAPI
devices, and the Block Descriptor Length in the Mode
Parameter Header shall be set to 0."
My thanks to qemu and the developers of its SCSI CD-ROM for showing
me this misconception in libburn.
MMC-3 also has some text saying that for compatibility you can have
block descriptors.
------------------------------------------------------------------------
If i do only -drive file=/dev/sr0,if=scsi,medium=cdrom i get
one empty drive, obviously from hw/ide/atapi.c:cmd_mode_sense():
MODE SENSE
5a 00 2a 00 00 00 00 00 1c 00
From drive: 28b
00 22 70 00 00 00 00 00 2a 12 3b 00 71 60 29 00 02 c0 00 02
02 00 02 c0 00 00 00 00
So i mistook the default DVD-ROM drive, which has no source data and
thus is empty, for the CD-ROM drive which i expected from -drive if=scsi
which would not be empty, but does not show up at all.
The question remains, why the CD-ROM drive is missing if i do -drive
but not -cdrom.
Ok, so we have something to test now. :)
I will repeat my experiments with
-drive file=/dev/sg2,if=scsi,media=cdrom -cdrom /dvdbuffer/pseudo_drive
Maybe the presence of -cdrom cures the problems i had with passthrough.
(The bug in libburn is not to blame for that. The passthrough drive did not
deliver a block descriptor.)
Yes, otherwise it wouldn't be passthrough. :)
------------------------------------------------------------------------
Yeah, looks like all the
case MODE_PAGE_R_W_ERROR: /* error recovery */
cpu_to_ube16(&buf[0], 16 + 6);
should have "- 2" instead of "+ 6".
I came to the same conclusion.
Good.
MMC-1 allows MODE SENSE(6), MMC-3 implicitely assumes MODE SENSE(10) only,
MMC-5 prescribes to use MODE SENSE(10).
MMC-2 has a list of required ATAPI commands. MODE SENSE(10) is listed.
MODE SENSE(6) is not listed.
I compared this with the SCSI counterpart of cmd_mode_sense():
hw/scsi-disk.c:scsi_disk_emulate_mode_sense()
It distinguishes between MODE_SENSE, which gets 4 bytes of header,
and MODE_SENSE_10, which gets 8. This looks correct.
Yep. Seems easiest to just drop MODE SENSE(6) from ATAPI.
Paolo
