Re: Sizing hardware drive capabilities (in the absence of probed devices)

[Don NetBSD <netbsd-embedded%gmx.com@localhost>]

On 9/16/2018 2:27 AM, Michael van Elst wrote:
> netbsd-embedded%gmx.com@localhost (Don NetBSD) writes:
>
> > Ah!  So, the sd(4) driver won't pass "non-scsi" commands and
> > the sd(4) devices might not accept scsi commands.  (damned if you
> > do, damned if you don't)?
>
> The sd driver just passes some byte sequence, some are intercepted by
> mfi, some aren't. The mfi firmware might do more before it actually
> reaches the disk.

The 2950 uses an mpt(4) -- though I suspect your points apply equally.

> > I'd have to make sure I numbered the targets on each scsibus as well.
>
> Yes, you need to wire scsibus (if there could be more than one) and
> you need to wire sd.

So, my kernel config should contain N+1 sd entries (the N+1th for a
wildcarded "sd?") each with specific unit numbers.  Ditto scsibus(4)'s
as well as the controller (mpt) to which they attach.  In this way, I
should be able to rely on the /dev mappings to specific hardware (even
in the absence of said hardware or portions thereof).

> > Yes, that's what I'm trying to guard against.  I can almost guarantee
> > that someone will get the "bright idea" that they can hack together a
> > second appliance -- using DIFFERENT hardware (a computer is a computer,
> > right?) and just cloning the system disk.  Then, complain when it
> > doesn't work as expected.
>
> You need to wire down scsibus to a specific controller. I.e. adding
> another controller or replacing it with a different model makes your
> kernel config void.

That's acceptable -- it's an *appliance*, not a "general purpose computer".
I just need to ensure that the software either knows that the configuration
has been changed (and can complain about it) *or* lock the system (hardware
and software) so it *can't* be changed.

(sigh)  This would be *so* much easier if I just pulled product off the Line
and tweeked the firmware!  "Want another?  Go get one (and *I* know it will
be identical to the last!)"