Re: [PATCH] sd: do not set changed flag on all unit attention conditions

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Tue, 2012-07-17 at 11:28 +0200, Paolo Bonzini wrote:
> Il 17/07/2012 11:11, James Bottomley ha scritto:
> > We don't do stuff just because the standards allows it; just the
> > opposite: we try to use the smallest implementations from the standards
> > we can get away with just because the more things we do, the more
> > exceptions and broken devices we come across.
> 
> Yes, I realize failing only on specific sense codes as I did it in the
> patch is not going to work.  However, the other way round is not
> problematic (explicitly allow some sense codes, fail on all others).

Heh, I once thought that, but there's no end to the strange ideas USB
manufacturers get.

> Another example is "target operating conditions have changed".  QEMU
> cannot report such changes because scsi_error prints a warning (fine)
> and then passes the unit attention upwards.  With removable drives, this
> has the same problem as resizing.

Why would a removable device ever use any of the codes under this ASC
when the medium hasn't changed?  They're all for arrays (well except
0x10 and 0x11 ... and they're only supposed to apply to tape changers
with autoload support declared in the control mode page).

The unanswered point is still that there's no use case for a device
that's both removable and requires array like sense code support.

James