[PATCH] cciss: adds MSI and MSI-X support

[PATCH] cciss: adds MSI and MSI-X support

This creates a new function, cciss_interrupt_mode called from
cciss_pci_init.  This function determines what type of interrupt vector to
use, i.e., MSI, MSI-X, or IO-APIC.

One noticeable difference is changing the interrupt field of the controller
struct to an array of 4 unsigned ints.  The Smart Array HW is capable of
generating 4 distinct interrupts depending on the transport method in use
during operation.  These are:

#define DOORBELL_INT 0
Used to notify the contoller of configuration updates. We only use
this feature when in polling mode.

#define PERF_MODE_INT 0
Used when the controller is in Performant Mode.

#define SIMPLE_MODE_INT 2
Used when the controller is in Simple Mode (current Linux implementation).

#define MEMQ_INT_MODE 3
Not used.

When using IO-APIC interrupts these 4 lines are OR'ed together so when any
one fires an interrupt an is generated.  In MSI or MSI-X mode this hardware
OR'ing is ignored.  We must register for our interrupt depending on what
mode the controller is running.  For Linux we use SIMPLE_MODE_INT
exclusively at this time.  Please consider this for inclusion.

Signed-off-by: Mike Miller <mike.miller@hp.com>
Cc: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>