Hello.
James Bottomley wrote:
Oh, yes. SCSI emulation is just what Linux embedded world is asking
for...
Well ATAPI is SCSI emulation (its a sort of pidgin SCSI admittedly).
ATAPI is SCSI transport (with maybe some quirks at SCSI command level
tho, IIRC). ATA is neither thansport nor does it map to SCSI 1:1.
Well, to be wholly accurate, since SCSI-3, SCSI has been separated into
an architecture, primary command, device specific command and transport
model (called the SCSI architecture model).
Thanks, I'm well aware of all this. :-)
My first encounter with SCSI dates back to 1993-94 -- it's a pity
that I had to abandon this area (switching to that puny IDE ;-)...
Starting with ATA-8, ATA
will go this way again.
It's gone that way in ATA/PI-7 actually, being broken into 3 separate
documents then, one spoecifying the command set and 2 others PATA and
SATA tranports.
What ATAPI actually is is a SCSI (really MMC
for CD and SSC for tape)
Unfortunately, the initial SFF documents specified both the transport
protocol and the command sets (which somewhat diverged form what SCSI-2
had, IIRC).
Fortunately, once ANSI finally taken over ATAPI work, they dropped
that stupid practice and started referring to MMC and SSC.
command transported over ATA using the ATA
PACKET command. With ATA-8 it will be much more analogous to SCSI
command over ATA transport.
I don't think "analogous" means that it will be sending SCSI CDBs
over PATA/SATA is of native commands and turn ATA into ATAPI. So all
this is fine but changes nothing about the SCSI emulation thing.
The code for emulating SCSI on ATA only burdens the kernel (and causes user
complaints about changing disk names from /dev/hdx to /dev/sda :-).
The code for sorting this out is already upstream in the block tree for
2.6.29.
Sorting out what, emulation?
I have to cut my response short that that point. I must be totally
crazy to allow myself to be dragged into this discussion having so much
work to do... :-/
MBR, Sergei
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