io_block_mapping in PPC64?

[Paul Mackerras]

Tzachi Perelstein writes:

> I don't know why you say that the io_block_mapping shouldn't be used.

It's because it makes (and imposes) assumptions about the layout of
kernel virtual address space, and it does so at the point where it is
called.  That point is in the caller of io_block_mapping, which is
usually in board setup code, distant from the mm code, which makes it
harder to maintain the mm code that lays out the kernel virtual space
and limits its flexibility.

In fact there is really no reason for platform and device drivers to
require a specific virtual address for their device.  It's not that
hard to store the virtual address in a variable and dereference
that. :)

Paul.