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Re: debian-hppa install notes with some CD trouble


Meelis Roos wrote:
> The only CD-related errors in dmesg are in the form of not being able to
> read past end of device:
> [...]
> [   35.918389] sr 0:0:6:0: [sr0] tag#46 Sense Key : 0x3 [current]
> [   35.973370] sr 0:0:6:0: [sr0] tag#46 ASC=0x6 ASCQ=0x0
> [   36.019042] sr 0:0:6:0: [sr0] tag#46 CDB: opcode=0x28 28 00 00 01 9c 2c 00 00 02 00
> [...]
> track:lout lba:    105518 (   422072) 23:28:68 adr: 1 control: 4 mode: -1

This is probably the CD-TAO-Read-Ahead bug.
It can be avoided by burning the CD with write type SAO (wodim option -sao).

Most CD drives report the media size including the two TAO Run-Out blocks,
which are not readable by SCSI command 28h READ(10). This is due to an
ambiguity of SCSI/MMC specs for command 25h READ CAPACITY which only some
few drives interpret like Linux expects.
See my futile attempt to bring it to the attention of linux-scsi

The remedy would be reading the last two blocks always separately from
previous blocks and to interpret their failure as End-Of-Medium if they are
not ASC 0x11 (read error) or ASC 0x15 (positioning error). No reliable
prediction of the readability of these sectors seems possible.

(I could need contact to a kernel developer for this and some other
 problems like:
 - Concurrent burn slowdown
 - Failure to wait for loaded tray to become ready
 - ioctl(BLKRRPART) refusing to re-assess CD/DVD/BD size after burning
 - undocumented old SCSI command feature used to determine start of last

Have a nice day :)


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