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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Nitesh Lal <nilal@redhat.com>,
        Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Marcelo Tosatti <mtosatti@redhat.com>
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Subject: Re: [PATCH tip:irq/core v1] genirq: remove auto-set of the mask when setting the hint
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Date:   Fri, 21 May 2021 13:56:10 +0200
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Nitesh,

On Thu, May 20 2021 at 20:03, Nitesh Lal wrote:
> On Thu, May 20, 2021 at 5:57 PM Nitesh Lal <nilal@redhat.com> wrote:
>> I think here to ensure that we are not breaking any of the drivers we have
>> to first analyze all the existing drivers and understand how they are using
>> this API.
>> AFAIK there are three possible scenarios:
>>
>> - A driver use this API to spread the IRQs
>>   + For this case we should be safe considering the spreading is naturally
>>     done from the IRQ subsystem itself.
>
> Forgot to mention another thing in the above case is to determine whether
> it is true for all architectures or not as Thomas mentioned.

Yes.

>>
>> - A driver use this API to actually set the hint
>>   + These drivers should have no functional impact because of this revert

Correct.


>> - Driver use this API to force a certain affinity mask
>>   + In this case we have to replace the API with the irq_force_affinity()

irq_set_affinity() or irq_set_affinity_and_hint()

>> I can start looking into the individual drivers, however, testing them will
>> be a challenge.

The only way to do that is to have the core infrastructure added and
then send patches changing it in the way you think. The relevant
maintainers/developers should be able to tell you when your analysis
went south. :)

Been there, done that. It's just lots of work :)

Thanks,

        tglx