Re: [Linux-usb-users] USB floppy drive no longer works under 2.6.15-rc6

Re: [Linux-usb-users] USB floppy drive no longer works under 2.6.15-rc6

[Jan De Luyck]

On Wednesday 28 December 2005 17:51, Matthew Dharm wrote:
> Can you try without ehci_hcd loaded?  The device is only full-speed anyway,
> so there should be no performance loss (like floppy has any performance to
> lose...)

Sorry for the delay, I was on some hard-needed vacation :)

I've tried it with ehci_hcd unloaded, but it shows the same problems, only 
with the same style of messages.

Anything else to try?

Jan

-- 
The real purpose of books is to trap the mind into doing its own thinking.
		-- Christopher Morley

Re: [Linux-usb-users] USB floppy drive no longer works under 2.6.15-rc6

[Alan Stern]

[Moved to linux-scsi]

On Mon, 9 Jan 2006, Matthew Dharm wrote:

> A long time ago, I noticed a quirk of the UFI specification in regards to
> one of the options for how to indicate a LUN isn't there.  Something about
> a special PDT, I think, in the INQUIRY respose.  I don't recall the
> details, but I do recall thinking something along the lines of "that's
> odd.. and it's going to confuse the SCSI core."
> 
> If I can find some time to search for that oddity of spec, then modify the
> UFI protocol handler to translate that oddity into a result code the SCSI
> core can understand, you can close the #2 case.

I see what you mean.  The UFI spec requires a device to return 0x1f in the
first byte of the INQUIRY response if no device is present at the LUN.  
That's Peripheral Qualifier = 0 and PDT = 0x1f (unknown or no device).  
Now SCSI-2 requires the value to be 0x7f to indicate no device, but UFI
also requires the returned SCSI level to be 0, and I don't know what
SCSI-0 says about reporting no device at a LUN.

Does anybody among the SCSI developers have the answer?  Should 
scsi_probe_and_add_lun() check for (result[0] & 0x1f) == 0x1f whenever 
(result[2] & 0x07) == 0?

If not, perhaps usb-storage should alter the returned value and max_lun
for a UFI device whenever we see 0x1f.

Alan Stern

Re: [Linux-usb-users] USB floppy drive no longer works under 2.6.15-rc6

[Matthew Dharm]

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On Tue, Jan 10, 2006 at 10:50:15AM -0500, Alan Stern wrote:
> [Moved to linux-scsi]
> 
> On Mon, 9 Jan 2006, Matthew Dharm wrote:
> 
> > A long time ago, I noticed a quirk of the UFI specification in regards to
> > one of the options for how to indicate a LUN isn't there.  Something about
> > a special PDT, I think, in the INQUIRY respose.  I don't recall the
> > details, but I do recall thinking something along the lines of "that's
> > odd.. and it's going to confuse the SCSI core."
> > 
> > If I can find some time to search for that oddity of spec, then modify the
> > UFI protocol handler to translate that oddity into a result code the SCSI
> > core can understand, you can close the #2 case.
> 
> I see what you mean.  The UFI spec requires a device to return 0x1f in the
> first byte of the INQUIRY response if no device is present at the LUN.  
> That's Peripheral Qualifier = 0 and PDT = 0x1f (unknown or no device).  
> Now SCSI-2 requires the value to be 0x7f to indicate no device, but UFI
> also requires the returned SCSI level to be 0, and I don't know what
> SCSI-0 says about reporting no device at a LUN.

SCSI-0 doesn't exist.  SCSI level 0 means "not really SCSI".

> Does anybody among the SCSI developers have the answer?  Should 
> scsi_probe_and_add_lun() check for (result[0] & 0x1f) == 0x1f whenever 
> (result[2] & 0x07) == 0?
> 
> If not, perhaps usb-storage should alter the returned value and max_lun
> for a UFI device whenever we see 0x1f.

That was my intention.  I've just never gotten around to doing it and
testing it.

Matt

-- 
Matthew Dharm                              Home: mdharm-usb@one-eyed-alien.net 
Maintainer, Linux USB Mass Storage Driver

Ye gods! I have feet??!
					-- Dust Puppy
User Friendly, 12/4/1997

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