So,
Looking at the SCSA code, it looks like there is a "new" API for DMA and
packet initialization. In particular, scsi_tran_setup_pkt(), when used
with the kmem_cache, also does the work to do the DMA initialization,
binding, etc. that HBA drivers are normally burdened with. (This
appears to be part of PSARC 2006/240. There is also 2005/680, but that
seems obsoleted by 2006/240.)
This is a good thing, since the code is pretty much the same with only
the dma attribute structure for a difference.
There is one wrinkle however. I may need to access the associated buf
(bp) for a packet instead of passing it off for DMA. This is necessary
if the HBA has to fall back to PIO, or if the driver needs to "fake" a
SCSI transaction. The wrinkle here is that none of the entry points
directly take a bp anymore. Even tran_start() doesn't get the bp.
OpenGrok finds me a routine called "scsi_pkt2bp()", which, IIUC, I
should be able to use. (Along with bp_mapin().) However, I can find
*no* callers for this code (maybe in usr/closed? I couldn't find any),
and there is no man page for the code.
So I want to use the function. Its in ON. Why isn't it documented?
Should I file a fast-track to open it? Or should another approach be used?
Btw, the man pages surrounding tran_setup_pkt() are bit sketchy on
details, and make a bogus reference to tran_setup_bp() (It looks like
that is left over from 2005/680, but was removed in the code but not the
man pages in 2006/240.). I think there is some opportunity to improve
the docs, at least.
-- Garrett
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