James Bottomley wrote on 2009-05-04:
On Mon, 2009-05-04 at 16:45 +0200, Stefan Richter wrote:
Ronald wrote at linux1394-user:
Linux doesn't support bigger than 2TB IEEE-1394 disk.
Will Linux have new driver for this issue?
(Adding Cc: linux-scsi)
As far as I can tell, Linux does support IEEE 1394 disks of any size.
However, if I'm not mistaken, disks larger than 2 TB require that the
READ CAPACITY (16) command is used to check the disk's capacity, rather
than the usual READ CAPACITY (10) command. Somebody correct me if I'm
wrong.
By far most firmwares of IEEE 1394/ SBP-2 chipsets implement only the
RBC (Reduced Block Commands) command set specification, or at least
claim so in their INQUIRY response. If I understood correctly, the
Linux SCSI stack will never send READ CAPACITY (16) to them since this
command is not included in RBC.
That's true ... but not quite the way we work. There's a standard
defined return for READ CAPACITY(10) which means ... I have more
sectors, please use READ CAPACITY (16). If we get that return, we'll
try again with READ CAPACITY (16) regardless of whether the device says
it's only RBC or not.
I obviously missed one other fact:
Initiator drivers need to tell the Linux SCSI core what the maximum
length of commands is that the driver is able to send to targets. Alas
our SBP-2 drivers do not specifiy a value for this (struct
Scsi_Host.max_cmd_len) and hence the core will send at most 12 bytes
long command blocks. But for disks > 2TB, we need 16 bytes long command
blocks.
I need to fix the SBP-2 drivers to set the limit correctly. This will
be a little more than one-liners though, I guess, because we need to
check a target capability datum before we set the length limit.
Stay tuned.
--
Stefan Richter
-=====-==--= -==- ===-=
http://arcgraph.de/sr/
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