Re: REPORT LUNS

[Patrick Mansfield <patmans@us.ibm.com>]

On Mon, Jun 16, 2003 at 08:55:18AM +0200, Josef Möllers wrote:
> Patrick Mansfield wrote:
> > 
> > On Fri, Jun 13, 2003 at 04:04:48PM +0200, Josef Möllers wrote:
> > > Hi,
> > >
> > > Wile trying to figure out how to ignore non-existing LUNs on RAID
> > > devices, I have fallen across an error in scsilun_to_int() where it
> > > doesn't behave as the comment suggests and a problematic piece of code
> > > in scsi_report_lun_scan().
> > >
> > > Patch is included.
> > 
> > If we clear the upper bits (address method, per SAM-3), someone has to
> > eventually set them again, and this is not handled today in linux scsi
> > core.
> 
> The comment said that the upper two bits were ignored which they were
> not in the original code, so, apart from fixing the shifts, I also added
> the mask to keep the code in sync with the comment. I haven't yet
> followed the use of the value thus created.

Ignored meaning "does nothing with it", when we should probably do
something - proper conversion, an error or warning output. The current
code might work (with high bits set), if we did not exceed the
host->max_lun. We might need an 8 byte lun everywhere to make it work
right for all cases.

Can you give more details of the problem you are seeing, and software
(adapter driver) and hardware in use?

I did not notice your shift changes - I don't see how they work or what
it fixes.

If scsi_lun was: 0x1 0x2 0x3 0x4 0 0 0 0

Current code:

First loop in scsilun_to_int, with i = 0:

	lun = 0 | ( (0x1 << 8 | 0x2) << 0) = 0x0102

Second loop i = 2:

	lun = 0x0102 | ( (0x3 << 8 | 0x4) << 16) = 0x03040102

Your patch would give:

First loop i = 0:

	lun = 0 | ((0x1 & 0x3f) << 1) | (0x2 << 0) = 0x02

Second loop i = 2:

	lun = 0x02 | ( ((0x3 & 0x3f) << 17) | (0x4 << 16) = 0x00060002

-- Patrick Mansfield
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