Jeff Garzik wrote:
Luben Tuikov wrote:
[Jeff Garzik wrote:]
* Put HCIL mapping into top-level helper code, for sharing between FC
and SAS (hopefully!)
One step further: eliminate the ugly legacy SPI-centric HCIL from
SCSI Core. Minimise and streamline SCSI Core.
How many times must we repeat: that's the long term goal.
Rome wasn't built in a day.
All transports implement HCIL mappings. (SPI drivers enjoy the easiest
mapping, hcil<->HCIL.) They are all faced with the necessity of mapping
and solve it in different ways, for different reasons. Why stop at FC +
SAS and try to find a unified solution for just those two? Also, when
you are working out how FC and SAS could interface to a common HCIL
mapping library (or HCIL mapping layer?), you are effectively designing
aspects of how an interface between FC|SAS and SCSI core should look
like. Or, why not provide the HCIL mapping helpers in the core and
subsequently make users of this new interface completely unaware of the
existence of HCIL...?
Moreover, HCIL mapping is but one aspect of a common problem. As an
example, I think yet another aspect of the same problem is that device
properties like target names and LUNs get lost below the
transport<->core interface. We want to present these device properties
to userspace in a unified manner. Here it becomes even more clear:
Neither is it a problem for FC and SAS alone, nor are transport-level
helpers a good solution to the problem.
I freely admit that I don't have a picture of where the real
difficulties lie; I am far too unfamiliar with the innards of scsi core.
But time spent on transport-level helpers which are meant to ease
symptoms of the transport<->core difficulties seems to be spent rather
ineffectively to me. More concrete, what is the ratio of benefit to cost
of HCIL mapping code sharing between SAS and FC? Especially since that
mapping is deemed obsolete already (in the long term or perhaps even mid
term). And to completely go back to the subject: Will attempts on code
sharing between FC layer and SAS layer bring things forward in the
short-term goal of SAS integration?
--
Stefan Richter
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http://arcgraph.de/sr/
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