From: Yinghai Lu on
On 03/21/2010 07:43 AM, Thomas Gleixner wrote:
> Eric,
> On Sun, 21 Mar 2010, Eric W. Biederman wrote:
>> With SPARSE_IRQ irq_to_desc becomes an unnecessary lookup operation on
>> the fast path of dispatching irqs to their handlers. We can avoid
>> this cost by passing an irq_desc pointer instead of using an integer
>> irq token to the irq_chip methods.
>> A single patch to convert all of the architectures is an unreviewable
>> 2000+ line patch. A gradual transition scenario with two sets of
>> irq_chip methods in irq_chip is an unmanageable mess in kernel/irq.
>> So instead I define some macros so the generic irq code in kernel/irq/
>> can compile either way based on a boolean Kconfig variable
>> CONFIG_CHIP_PARAM_DESC. This allows us to convert one architecture at
>> a time, reducing the follow on patches to manageable proportions. It
>> is a little bit ugly but it is much better than the alternatives, and
>> as soon as we finish the transition we can kill the macros.
>> I introduce the macros CHIP_ARG, CHIP_VAR, and CHIP_PARAM where
>> appropriate. I change a few declarations of irq as int to unsigned
>> int. I normalize the variables names in the functions that call
>> chip methods to ensure that I have the variables irq and desc present
>> allowing CHIP_ARG to work properly. Most importantly none of the irq
>> logic changes with this patch.
> I like that approach very much. Is the output binary equivivalent?

will update x86 part and related core according to this, and give it a try.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)
More majordomo info at
Please read the FAQ at