Theodore Tso wrote:
On Wed, Nov 29, 2006 at 09:44:59AM -0800, Dan Nicolaescu wrote:
Hi,
In 8250.c is_real_interrupt is defined like this:
/*
* We default to IRQ0 for the "no irq" hack. Some
* machine types want others as well - they're free
* to redefine this in their header file.
*/
#define is_real_interrupt(irq) ((irq) != 0)
on my platform the UART IRQ is 0, so is_real_interrupt returns
false.
In order to allow machines to override is_real_interrupt, and for the
code to match the comment shouldn't this patch be applied?
No, IRQ 0 for linux is always "no IRQ". We should probably add this
to the LKML FAQ, since it keeps coming up. Per Linus, if there are
any architectures that has a valid IRQ #0, then the
architecture-specific kernel code should remap IRQ numbers. See:
http://comments.gmane.org/gmane.linux.kernel/468449
- Ted
My reading of the messages you linked to is that is_real_interrupt
should eb defined as
#define is_real_interrupt(irq) ((irq) != NO_IRQ)
where NO_IRQ may be defined differently for platforms where IRQ #0 is
valid,
not that IRQ 0 is always "no IRQ"
I have not done any low level x86 linux work, but even on an x86 IRQ 0
is valid.
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Dave Lynch DLA Systems
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