irq.h changes in 2.3.14

irq.h changes in 2.3.14

[Jes Sorensen]

Hi

I noticed the moving of arch/i386/kernel/irq.h to include/linux/irq.h in
the 2.3.14 final patch.

I really don't think it is a good idea to move this very i386 specific
definitions in there since the interrupt subsystems on other
architectures are very different from that of the i386. Ie. on the m68k
we do not use the same types or irq descriptors, the IRQ line statuses
make no sense etc. and I am sure it is the same for some of the other
non x86 architectures.

I see that it expects asm/hw_irq.h to be the architecture dependant
stuff, but even the things that made it into include/linux/irq.h are way
to architecture specific.

Putting this include file in include/linux/irq.h with a generic name
like that means someone is going to use it in the generic kernel code at
some point. Having the common kernel code relying on such x86 specific
features is going to be a pain for us to handle at that point.

The only things I can see being architecture independant is the
irq_{enter,exit}() stuff and even then I am not sure the SMP versions
are portable enough for non x86 machines (being able to do test_bit() on
a spin lock is fairly implementation specific).

I really think those bits should be moved out of the generic header
files to avoid problems.

Jes

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Re: irq.h changes in 2.3.14

[Linus Torvalds]

On Thu, 19 Aug 1999, Jes Sorensen wrote:
> 
> I noticed the moving of arch/i386/kernel/irq.h to include/linux/irq.h in
> the 2.3.14 final patch.
> 
> I really don't think it is a good idea to move this very i386 specific
> definitions in there since the interrupt subsystems on other
> architectures are very different from that of the i386.

The thing is, that the irq handling is _too_ different on different
architectures. A lot of the problems, especially the SMP issues, are
simply completely architecture-independent. 

>					 Ie. on the m68k
> we do not use the same types or irq descriptors, the IRQ line statuses
> make no sense etc. and I am sure it is the same for some of the other
> non x86 architectures.

It is. And I _know_ that just about every architecture except for the x86
has bugs when it comes to SMP handling. Some, like the 68k, do not need to
care. 

> I see that it expects asm/hw_irq.h to be the architecture dependant
> stuff, but even the things that made it into include/linux/irq.h are way
> to architecture specific.

There's absolutely nothing architecture-specific in <linux/irq.h>.

It may be _different_ than existing architectures, but I'll try to make
sure that future ports use the same correct irq handling, and I'll see if
I can port some of the existing stuff (notably alpha) to use the new
generic handling. It's actually very flexible - it pretty much has to be
in order to handle the different kinds of interrupt controllers that exist
on PC-like machines.

No architecture will be _forced_ to use the new stuff, so don't worry. But
I'll just warn you that you're likely to get the SMP stuff wrong if you
don't use it ;)

			Linus


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