[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

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=80711

--- Comment #9 from Tiziano Bacocco <tiziano.bacocco@gmail.com> ---
(In reply to Alan Stern from comment #8)
> On Wed, 6 Aug 2014, Christoph Hellwig wrote:
> 
> > 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?
> 
> No, the patch that started this Bugzilla entry.  Tiziano says it is 
> needed in order to send vendor-specific commands that use the LUN bits 
> in CDB[1].
> 
> > > > 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.
> 
> I tried connecting a Linux mass-storage gadget with two logical units
> to a host PC running Windows 7.  The host scanned the first logical
> unit and completely ignored the second!  Didn't even send an INQUIRY 
> command.
> 
> So the question remains unanswered...
> 
> Can someone tell me if anything special is needed to make Windows
> recognize logical units beyond the first?
> 
> Alan Stern

That's weird , old android phones which use multiple LUNs and Linux usb gadgets
, had internal memory and SD card , and they worked on windows

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