Why do we have the orm device?

[M. Warner Losh]

In message: <44138F0A.8000606 at bitfreak.org>
            Darren Pilgrim <darren.pilgrim at bitfreak.org> writes:
: I see it on all of my machines and have never seen it used by anything. 
:   The orm(4) man page says it's part of ISA bus support and is designed 
: to claim ROMs sitting in the memory address space, but doesn't go into 
: any detail why it's necessary to prevent other drivers from using ROM 
: addresses.
: 
: So why do we have this device?

The ROMs that sit on the ISA bus in expansion cards and as part of
video support cannot be used for other purposes.  orm prevents that by
allocating those resources.

This prevents collisions with old ISA devices like 16-bit PC Card
bridges, many network cards that have shared memory, as well as some
scsi cards that also do the same.  Many of these ISA devices have the
ability to set which address range to use.  If there's a ROM where the
driver picks, then it just won't work.  You can't have two devices
decode the same address.

Warner