Re: [Bug 80711] [PATCH]SG_FLAG_LUN_INHIBIT is no longer implemented and there's not way to prevent the kernel from using the 2nd cdb byte for the LUN

Christoph Hellwig
2014-08-07T06:39:19Z

On Wed, Aug 06, 2014 at 04:02:22PM -0400, Alan Stern wrote:
> > I doubt either of them forces users to hack up flags for these cases.
>
> Why was this change needed in the first place? There's no explanation
> in the patch itself.

Which chance? The one to not support SG_FLAG_LUN_INHIBIT?

>
> > At least for windows I suspect it just never sends the LUN encoded
> > in the CDB and treats USB devices special instead of our insistance
> > on pretending they are SCSI-2.
>
> We no longer pretend that USB mass-storage devices have any particular
> SCSI level. See commit 09b6b51b0b6c.

So the origina reported device must report SCSI-2 all by itself if he's
running a recent kernel, ok.

> > Maybe some of the USB people have on the wire traces or access to
> > device or windows documentation on this?
>
> Most likely it varies with the version of Windows and the INQUIRY data
> returned by the device.
>
> I can obtain hardware traces for the kinds of devices and computers
> lying around here. But what sort of combinations should I test?

I'd mostly be interested to see if it actualy encodes the LUN in the CDB
for any USB multi-LUN device.