Florent Thoumie wrote:
On Tuesday 31 January 2006 02:00, Nate Lawson wrote:
Florent Thoumie wrote:
It seems a lot of devices are concerned by the sync cache problem, would
it be harmful to just remove this part of the code or could there be a
way to detect if the device supports it or not?
Well, it's important to run SYNC_CACHE in shutdown or possibly when
unmounting a filesystem. Otherwise, data could be lost on boot.
However, I support adding a USB-specific mechanism that says SYNC_CACHE
should only be run on shutdown or device_eject, that way devices that
hang after this command is run would still work at runtime. And SCSI
devices that support multiple calls to SYNC_CACHE (i.e. most non-USB
devs) would still work too.
However, the first step is to investigate what windows and Linux do.
Linux only sends the SYNCHRONIZE_CACHE command if the WCE (Write Cache Enable)
bit of the disk is set. I can't seem to find something equivalent to this in
our CAM framework. I have no particular SCSI knowledge but I guess I can have
a look at this tomorrow.
I'm forwarding this to freebsd-scsi@ (keep me CC'ed, as I'm not subscribed to
this list, yet).
Hmm, is WCE part of the inquiry response? [moving to scsi@ list]
--
Nate
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