cvs commit: src/sys/cam/scsi scsi_da.c src/sys/dev/usb umass.c usbdevs

[Nate Lawson]

Florent Thoumie wrote:
> On Tuesday 31 January 2006 06:33, Matthew Jacob wrote:
> 
>>>>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]
>>
>>Yes.
> 
> 
> Hum, reading Linux source and SCSI standard [1], I'm not so sure, but I might 
> be wrong. We need to request the caching page in scsi_mode_sense_{6,10}.
> 
> I'll try to write something today, but I guess someone having already worked 
> on scsi will only need 10 minutes to DTRT.
> 
> [1] http://www.danbbs.dk/~dino/SCSI/SCSI2-09.html (table 156)
> 

You might also want to check if we or Linux set the Immediate bit as 
part of the SYNCHRONIZE CACHE command.  It's possible that USB devices 
don't properly parse that bit.

I think the tape driver (sa) does MODE SENSE as part of normal operation 
but da does not.  (Working frm memory here).

-- 
Nate