cdrecord and scsi-3 compliance
SCSI-3 specification has effectively removed LUN address from command
data block (it was moved to lower transport layer so to say). Therefore
assigning of cdb.g5_cdb.lun [as commonly performed by cdrecord] is
*formally* inappropriate, inappropriate in SCSI-3 context that is.
Indeed, the field specified as LUN by SCSI-2 is declared "reserved" in
*all* SCSI-3 drafts. Where "reserved" per definition is
"A keyword referring to bits, bytes, words, fields and code values that
are set aside for future standardization. A reserved bit, byte, word or
field *shall* be set to zero, or in accordance with a future extension
to this standard."
Where "shall" is defined as
"A keyword indicating a mandatory requirement. Designers are required to
implement all such mandatory requirements to ensure interoperability
with other standard conforming products."
So that *formally* application program such as cdrecord should basically
figure out SCSI level implemented by the targer and abstain from
assigning the cdb.g5_cdb.lun, if level was found to be larger than 2. As
fast-acting "relief" I would suggest to reimplement 'scg_lun(scgp)'
macro as '(scsi_level>2?0:(scgp)->addr.lun)'. But *formally* it is
assignment operator as a whole, which should be made conditional, i.e.
'if (scsi_level>2) cdb.g5_cdb.lun=scg_lun(scgp);' in SCSI level
"neutral" code pathes, and it should be simply removed in SCSI-3
specific code such as MMC driver(s) (MMC was initially formed as part of
SCSI-3 specifications family).
This naturally implies that scsi_level variable is declared and assigned
a sane value. Unfortunately there is no apparent *reliable* way to
establish target's SCSI level compliance, at least because version
fields in INQUIRY result don't match between SCSI and ATAPI
specifications. So we either have to be creative or require user to
manually identify at least ATAPI units by specifying ATAPI:/dev/xxx or
similar. Thoughts? As for "being creative." At the very least one should
be able to *reliably* use GET CONFIGURATION command to identify MMC
compliant units (MMC implies scsi_level=3!), as well as to identify
ATAPI units (physical interface is returned as part of feature code 1,
but it might be unreliable(?)). A.
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