rapidio: make enumeration/discovery configurable

rapidio: make enumeration/discovery configurable

Systems that use RapidIO fabric may need to implement their own
enumeration and discovery methods which are better suitable for needs of a
target application.

The following set of patches is intended to simplify process of
introduction of new RapidIO fabric enumeration/discovery methods.

The first patch offers ability to add new RapidIO enumeration/discovery
methods using kernel configuration options.  This new configuration option
mechanism allows to select statically linked or modular
enumeration/discovery method(s) from the list of existing methods or use
external module(s).

This patch also updates the currently existing enumeration/discovery code
to be used as a statically linked or modular method.  The corresponding
configuration option is named "Basic enumeration/discovery" method.  This
is the only one configuration option available today but new methods are
expected to be introduced after adoption of provided patches.

The second patch address a long time complaint of RapidIO subsystem users
regarding fabric enumeration/discovery start sequence.  Existing
implementation offers only a boot-time enumeration/discovery start which
requires synchronized boot of all endpoints in RapidIO network.  While it
works for small closed configurations with limited number of endpoints,
using this approach in systems with large number of endpoints is quite
challenging.

To eliminate requirement for synchronized start the second patch
introduces RapidIO enumeration/discovery start from user space.

For compatibility with the existing RapidIO subsystem implementation,
automatic boot time enumeration/discovery start can be configured in by
specifying "rio-scan.scan=1" command line parameter if statically linked
basic enumeration method is selected.

This patch:

Rework to implement RapidIO enumeration/discovery method selection
combined with ability to use enumeration/discovery as a kernel module.

This patch adds ability to introduce new RapidIO enumeration/discovery
methods using kernel configuration options.  Configuration option
mechanism allows to select statically linked or modular
enumeration/discovery method from the list of existing methods or use
external modules.  If a modular enumeration/discovery is selected each
RapidIO mport device can have its own method attached to it.

The existing enumeration/discovery code was updated to be used as
statically linked or modular method.  This configuration option is named
"Basic enumeration/discovery" method.

Several common routines have been moved from rio-scan.c to make them
available to other enumeration methods and reduce number of exported
symbols.

Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Li Yang <leoli@freescale.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Andre van Herk <andre.van.herk@Prodrive.nl>
Cc: Micha Nelissen <micha.nelissen@Prodrive.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>