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From: ebiederm@xmission.com (Eric W. Biederman)
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Subject: [PATCH 0/25] Decouple IRQ issues (MSI, i386, x86_64, ia64) 
Date: Tue, 20 Jun 2006 16:24:35 -0600
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The following patchset is against 2.6.17-rc6-mm2.
It was the only easy place I could get everyones work who has been
touching relevant code.

The primary aim of this patch is to remove maintenances problems caused
by the irq infrastructure.  The two big issues I address are an
artificially small cap on the number of irqs, and that MSI assumes
vector == irq.  My primary focus is on x86_64 but I have touched
other architectures where necessary to keep them from breaking.

- To increase the number of irqs I modify the code to look at
  the (cpu, vector) pair instead of just  looking at the vector.

  With a large number of irqs available systems with a large irq
  count no longer need to compress their irq numbers to fit.
  Removing a lot of brittle special cases.

  For acpi guys the result is that irq == gsi.

- Addressing the fact that MSI assumes irq == vector takes a few more
  patches.  But suffice it to say when I am done none of the generic
  irq code even knows what a vector is.

In quick testing on a large Unisys x86_64 machine we stumbled over at
least one driver that assumed that NR_IRQS could always fit into an 8
bit number.  This driver is clearly buggy today.  But this has become
a class of bugs that it is now much easier to hit. 

I've done my best but if this patchset wasn't perfect it won't
surprise me.  But I'm pretty certain I have succeeded in decoupling
any fixes should be small and well contained.

Eric