Re: ioperm and pseudo devices

[Roland McGrath]

> I think we need a flag in the device structure to mark the type of the
> device more properly than the device ops does.  In particular, I am worried
> about someone sending an io perm modify IPC to a non-io perm device port, it
> doesn't look to me as if I coded any guard against this into it.

That RPC goes to the task.  You are talking about its argument.
convert_io_perm_to_port needs to check that it's really an io_perm port.

As it happens, I don't think that any other device uses no_device_ops (I
don't recall what it was there for in the first place).  So you could use
ops==&no_device_ops as the test.  Or to avoid the presumption you could
just make your own all-zeros io_perm_device_ops so that the address would
be unique.

It seems to me we might actually want a device_ops anyway, to have close.
Then io_perm.c could use the oskit interfaces for the global io bitmap,
to disallow an io_perm range that overlaps with a kernel driver.